3

INTRODUCTION

Pharmaceutical chemistry – is the chemistry of drugs and the science which is

developing rapidly. Quality control is integral to all modern processes and the

pharmaceutical industry is no exception. Testing a pharmaceutical product involves

chemical, physical and sometimes microbiological analyses. Each year lots of new

biologically active compounds are synthesized and new drugs are appeared on the

pharmaceutical market, and methods of synthesis and analysis of the traditional

medicines (so called "generics") are improved.

That is why the authors did not want to cover absolutely all the methods of

preparation or analysis of drugs, and made their generalizations to provide concrete

material for example, giving the most typical representatives of certain groups of

drugs that will allow students to study program material creatively.

This textbook has been designed primarily for students of pharmaceutical

universities and departments of pharmacy in higher educational establishments.

During writing this textbook it was assumed that students of III-V years

already have sufficient knowledge of chemistry, to avoid excessive increase in the

volume of the book, the authors refused to repeat certain reactions.

In the section "Identification" and "Limit tests," which refers determination of

certain ions (when the opposite ion is unknown or not named) interact with a specific

method given in substance (substances), we consider that it is appropriate to give the

reactions in ion-molecular form. In other sections reactions are given mainly in

molecular form. Some complex reactions of organic substances are schematic and not

balanced.

The textbook consists of two parts. In the first part analysis of medicinal

substances of inorganic, aliphatic and aromatic structure is given. The second part

involves main methods of analyses for medicinal substances of heterocyclic structure

and natural origin. Main methods for identification and assay are given according to

European Pharmacopoeia and State Pharmacopoeia of Ukraine, but at the same time

the most widely used and specific reactions not included into Pharmacopoeias are

also given.

In the first and second parts of the textbook features of the pharmaceutical

analysis of drugs in groups according to the composition and chemical structure are

discussed: inorganic - by groups of periodic table, organic - in accordance with the

presence of functional groups, the natural biologically active compounds - by the

chemical structure and biological effects (alkaloids, glycosides, vitamins, hormones,

antibiotics, etc.).

Each group of drugs is described in a separate section by the following plan:

general characteristic, physical and chemical properties, ways or schemes of

preparation, reactions and methods of identification, tests for purity, and the most

widely used methods for quantitative determination, special storage conditions,

pharmacological action and usage in medical practice. The most attention is paid to

the modern medicines and methods for their research.

The authors are grateful for critical comments and suggestions, which will be

considered in future work on the textbook of pharmaceutical chemistry.

4

Chapter 1. SUBJECT OF PHARMACEUTICAL CHEMISTRY

IDENTIFICATION AND TESTS FOR PURITY

Plan

1. Subject of pharmaceutical chemistry.

2. Structure of Pharmacopoeia and of a monograph.

3. General reactions for identification of inorganic preparations.

4. Tests for purity:

general questions on impurity determination;

clarity and degree of opalescence of liquids;

degree of coloration of liquids;

determination of pH;

loss on drying and determination of water;

limit tests.

Subject of pharmaceutical chemistry

Pharmaceutical chemistry studies chemical structure, preparation, physical

and chemical properties of medicinal substances, their identification, assay and

determination of impurities, storage of the preparations and their use in medicine,

methods of standardization of medicines, structure-activity relationships for the

preparations.

Pharmaceutical chemistry is one of the most important disciplines for the

pharmacists. It gives very important knowledge about chemical properties of

medicinal preparations. These properties have great influence on the pharmacological

activity because the behaviour of preparations depend on their solubility in different

solvents, possibility to interact with biological systems and other preparations, to

participate in biochemical processes, to form different metabolites etc.

Pharmaceutical chemistry is based on the other chemical sciences such as inorganic,

organic, analytical, physical, colloidal chemistry, and pharmacology.

Pharmaceutical analysis is one of the main parts of pharmaceutical chemistry.

Its objects are medicinal substances and medicinal preparations produced on

pharmaceutical plants or in the chemist’s.

Substance is the standardized biologically active compound or standardized

mixture of such compounds used for the medicines’ preparation.

The main document standardizing the quality of the medicinal substances and

medicinal preparations is Pharmacopoeia. European pharmacopoeia is legislative for

the many countries of Europe. State Pharmacopoeia of Ukraine is legislative in

Ukraine. Pharmacopoeia is a legal act, which contains general requirements for the

preparations, monographs, and methods of medicines standardization.

Pharmacopoeia’s requirements are obligatory for all the enterprises of the country,

which produce, analyze, store, and realise the medicaments.

5

Structure of Pharmacopoeia and of a monograph

Pharmacopoeia has two large parts: general methods and monographs for the

substances (in European Pharmacopoeia there are no monographs for the dosage

forms because their quantity nowadays is great).

All monographs have the same structure.

At the beginning of each monograph, there are international and chemical

names of the substance. Then graphic and molecular formulas of the substance and its

molecular weight are given.

Definition contains the limits of content of a substance. An upper limit

exceeding 100 % may be stated, e.g. 101 %. It means that the result of the assay is

not more than 101 %, calculated in terms of the equivalent content of compound.

Characters give the appearance of the substance and its solubility.

Identification is the important part of the monograph. The tests given in this

part of the monograph do not establish absolute proof of identity, but they provide a

means of verifying that the identity of the material being examined is in accordance

with the label on the container. Depending on the chemical nature of the substance,

the combination of different physico-chemical methods with chemical reactions is

used for the identification.

Certain monographs have subdivisions “First identification” and “Second

identification”. The tests of “Second identification” can be used instead of the test or

tests of the “First identification” provided it could be demonstrated that the substance

or preparation is fully traceable to a batch certified to comply with all the

requirements of the monograph.

Each substance can contain different foreign compounds, called impurities.

That is why another very important part of a monograph is tests: appearance of the

solution (clarity and degree of opalescence of liquids and degree of coloration of

liquids), acidity or alkalinity, tests of permitted limits of certain impurities, etc. The

concentration of certain impurities is given either as a percentage or in parts per

million by weight (ppm). Quantity of such impurities should not exceed the stated

limit. There are also impurities, which could not be discovered at all by the methods

described (limits for them are not stated).

The assay gives the method for the quantitative analysis of a substance in order

to know the limits of its content.

Storage expresses conditions of storage of a substance.

At the end of a monograph, there are labelling and action and use.

General reactions for identification of inorganic preparations

Among other methods of analyses given in European Pharmacopoeia, there are

general reactions of ions (anions and cations) and functional groups, given into the

general article “Identification reactions of ions and functional groups”.

In this part, we will discuss identification reactions for inorganic ions only.

6

ALUMINIUM

No precipitate is formed after adding of thioacetamide reagent to the

aluminium salt solution in the presence of dilute hydrochloric acid (absence of heavy

metals salts). After adding of sodium hydroxide solution a gelatinous white

precipitate is formed which dissolves on further addition of the reagent:

Al3+

+ 3NaOH Al(OH)3+ 3Na+

Al(OH)3 + 3NaOH Na3[Al(OH)6]

The gelatinous white precipitate is reformed after adding of ammonium

chloride solution.

Na3[Al(OH)6] + 3NH4Cl Al(OH)3 +3NH4OH +3NaCl

AMMONIUM SALTS

For the emission of ammonium from its salts, magnesium oxide is added to the

prescribed solution of the substance. Then a current of air is passed through the

mixture and the escaping gas is directed on the surface of a mixture of 0,1M

hydrochloric acid and methyl red solution. The colour of the indicator changing to

yellow shows the presence of ammonium salts.

NH3 + HCl NH4Cl

The solution obtained forms yellow precipitate in reaction with sodium

cobaltinitrite solution:

2NH4Cl + Na3[Co(NO2)6] (NH4)2Na[Co(NO2)6] + 2NaCl

AMMONIUM SALTS AND SALTS OF VOLATILE BASES

After heating of the preparation with sodium hydroxide solution, the reaction

mixture gives off vapour that can be identified by its odour and its alkaline reaction. to

NH4+ + OH

- NH3 + H2O

ARSENIC

a) After heating of the prescribed solution on a water-bath with an equal

volume of hypophosphorous reagent a brown precipitate is formed.

NaH2PO

2 + HCl → H3PO2 + NaCl

As2O3 + 3H3PO2 → 2As + 3H3PO3

As2O5 + 5 H3PO2 → 2As + 5 H3PO3

The State Pharmacopoeia of Ukraine additionally uses the following two

identification reactions of arsenic compounds:

b) Identification of arsenic (III) (arsenites):

The solution of the substance gives yellow precipitate after adding of dilute

hydrochloric acid and sodium sulphide solution. The formed precipitate dissolves on

addition of ammonia.

As2O3 +6HCl 2AsCl3 + 3H2O

2AsCl3 + 3Na2S As2S3 + 6NaCl

As2S3 + 6NH4OH (NH4)3AsO3 + (NH4)3AsS3 + 3H2O

c) Identification of arsenic (V) (arsenates):

7

The prescribed solution reacts with ammonium chloride, ammonia and

magnesium sulphate solution forming a white, crystalline precipitate, which dissolves

on addition of dilute hydrochloric acid. (This reaction is used for distinction arsenates

from arsenites).

Na2HAsO4 + MgSO4 + NH4OH ClNH4 NH4MgAsO4 + Na2SO4+ H2O

BISMUTH

a) Bismuth preparations react with sodium sulphide solution giving brown

precipitate. Reaction is carried out after dissolving of preparation in hydrochloric

acid and heating to boiling and cooling the mixture (filtering if necessary). Then after

adding of water, a white or slightly yellow precipitate is formed (due to the formation

of the oxychloride BiOCl). After adding of reagent, it turns brown.

2Bi3+

+ 3Na2S Bi2S3 + 6Na+

b) For this reaction the solution is boiled with dilute nitric acid. The solution

obtained reacts with thiourea solution forming a yellowish-orange colour or an

orange precipitate. After adding of sodium fluoride solution, the obtained solution is

not decolourised within 30 min.

Bi3 3(NH2)2CS [Bi((NH2)2CS)3]

3

BROMIDES

a) Silver nitrate solution in the presence of dilute nitric acid gives a curdled,

pale yellow precipitate, which dissolves with difficulty in ammonia.

Br- + AgNO3 AgBr + NO3

-

AgBr + 2NH4OH [Ag(NH3)2]Br + 2H2O

b) In this reaction free bromine is formed after interaction with lead dioxide in

the presence of acetic acid. Free bromine brominates fuchsin (this reaction is carried

out on the filter paper strip impregnated by decolorized fuchsin solution). Due to the

forming of bromosubstituted fuchsin a violet colour appears on the filter paper.

c) The State Pharmacopoeia of Ukraine additionally uses the following

reaction. Bromides are oxidized by chloramine solution in the presence of dilute

hydrochloric acid and chloroform with the forming of free bromine. Due to the

extraction of bromine chloroform layer is coloured yellowish-brown.

CH

3

SO2N

Cl

Na

CH3

SO2NH

2

+ 2HCl + Cl2 + NaCl

2Br - + Cl2 Br2 + 2 Cl -

8

CALCIUM

a) Reaction with glyoxal hydroxyanile alcohol solution. This reaction is carried

out in basic conditions (presence of dilute sodium hydroxide solution and sodium

carbonate solution). After shaking of the reaction mixture with chloroform and

adding water the chloroform layer is coloured red.

Ca2+

H+

N

OH

N

OH

CH CH N

O

N

O

CH CH

Ca

+ +2

NaOH

Na2CO3

CHCl3

b) Substance is dissolved in acetic acid. After adding of potassium

ferrocyanide solution the solution remains clear (absence of iron salts). On addition

of ammonium chloride a white, crystalline precipitate is formed:

Ca2+

+ 2NH4+ + K4[Fe(CN)6] (NH4)2Ca[Fe(CN)6] + 4K

+

The next two reactions of calcium ions are additionally used by the State

Pharmacopoeia of Ukraine, reaction c) is used also in EP for the test for calcium.

c) After adding of ammonium oxalate solution to the prescribed solution a

white precipitate of calcium oxalate is formed. It does not dissolve in dilute acetic

acid and ammonia and dissolves in dilute mineral acids.

Ca2+

+ (NH4)2C2O4 CaC2O4 + 2NH4+

d) Calcium salt, treated with hydrochloric acid and put into the colourless

flame, makes it orange-red.

CARBONATES AND BICARBONATES a) After adding of dilute acetic acid to the solution (or the suspension) of the

substance colourless and odourless gas (carbon dioxide) is formed by both carbonates

and hydrocarbonates.

CO32-

+ 2CH3COOH CO2 + H2O + 2CH3COO-

HCO3- + CH3COOH CO2 + H2O + CH3COO

-

This gas collected in barium hydroxide solution gives a white precipitate that

dissolves on addition of an excess of hydrochloric acid.

CO2 + Ba(OH)2 BaCO3 + H2O

BaCO3 + 2HCl BaCl2 + CO2 + H2O

There are two reactions, used by the State Pharmacopoeia of Ukraine, which

help to distinguish hydrocarbonates from carbonates:

b) In reaction with magnesium sulphate solutions of carbonates give a white

precipitate. Bicarbonates give a precipitate only after boiling:

4Na2CO3 + 4MgSO4 + 4H2O 3MgCO3∙Mg(OH)2∙3H2O↓ + 4Na2SO4 + CO2↑

2HCO3- + MgSO4 → Mg(HCO3) + SO4

2-

tº

Mg(HCO3) → MgCO3↓ + CO2↑ + H2O

c) Carbonates solutions become violet-red after adding of phenolphthalein.

Bicarbonates solutions stay colourless.

9

CHLORIDES

a) Chlorides give curdled, white precipitate with silver nitrate solution in the

presence of dilute nitric acid. Precipitate dissolves easily in ammonia.

Cl- + AgNO3 AgCl + NO3

-

AgCl + 2NH4OH [Ag(NH3)2]Cl + 2H2O

b) After chlorides interaction with potassium dichromate and sulphuric acid the

chromyl chloride is formed. This gas colours a filter-paper strip impregnated with

diphenylcarbazide solution into violet-red.

4Cl- + K2Cr2O7 + 3H2SO4 2CrO2Cl2 + K2SO4 + 3H2O + 2SO4

2-

O=CNH-NH-C6H5

NH-NH-C6H5

O=CNH-NH-C6H5

N=N-C6H5

CrO2Cl2

N=N-C6H5

C OH

N-NH-C6H5Ñr

2+ +

N=N-C6H5

C OH

N-NH-C6H5

Cr2 + 2

N=N-C6H5

C O

N-NH-C6H5

Cr

C6H5-N=N

CO

C6H5-HN-N

+ 2H

IODIDES a) Silver nitrate solution in the presence of dilute nitric acid gives a curdled,

pale-yellow precipitate, which does not dissolve in ammonia:

I- + AgNO3 AgI + NO3

-

b) Free iodine is formed after reaction of iodides with potassium dichromate

solution in the presence of dilute sulphuric acid. After shaking of reaction mixture

with chloroform the chloroform layer is coloured violet or violet-red.

6KI + K2Cr2O7 +7H2SO4 3I2 + Cr2(SO4)3 + 4K2SO4 + 7H2O

IRON

In EP there are one reaction for Fe2+

identification and two reactions for Fe3+

.

a) Potassium ferricyanide solution gives with ferrous (Fe2+

) salts a blue

precipitate that does not dissolve after adding of dilute hydrochloric acid:

3Fe2+

+ 2K3[Fe(CN)6]3‾

Fe3[Fe(CN)6]2↓ + 6K+

b) Potassium thiocyanate solution gives with ferric (Fe3+

) salts complex of red

colour:

Fe3+

+ 3KSCN [Fe(SCN)3] + 3K+

After adding of isoamyl alcohol or ether to one portion of reaction mixture

organic layer is coloured pink. After adding of mercuric chloride solution to the

second portion of red mixture the red colour disappears:

2[Fe(SCN)3 ]+ 3HgCl2 3[Hg(SCN)2] + 2FeCl3

c) Potassium ferrocyanide solution gives with ferric salts a blue precipitate that

does not dissolve after adding of dilute hydrochloric acid:

4Fe3+

+ 3K4[Fe(CN)6] Fe4[Fe(CN)6]3↓ + 12K+

10

LEAD

a) Reaction with potassium chromate solution with formation of yellow

precipitate that dissolves on addition of strong sodium hydroxide:

Pb2+

+ K2CrO4 PbCrO4 + 2K+

PbCrO4↓ + 4NaOH Na2[Pb(OH)4] + Na2CrO4

b) Potassium iodide solution gives a yellow precipitate, disappearing on

boiling and re-forming after cooling, as glistening, yellow plates.

Pb2+

+ 2KI PbI2 + 2K+

MAGNESIUM

Dilute ammonia gives with magnesium ions a white precipitate that dissolves

on addition of ammonium chloride solution:

Mg2+

+ 2OH- Mg(OH)2

Mg(OH)2 + 2NH4Cl MgCl2 + 2NH4OH

Then disodium hydrogen phosphate solution gives a white crystalline

precipitate: NH4Cl

Mg2+

+ Na2HPO4 + NH4OH NH4MgPO4 + H2O + 2Na+

MERCURY

a) When the solution of mercuric salts is placed on well-scraped copper foil, a

dark-grey stain is formed. It becomes shiny on rubbing. After drying and heating of

the foil in a test-tube the spot disappears (metallic mercury sublimates).

Hg2+

+ Cu Hg↓ + Cu2+

b) In strongly alkaline conditions mercury salts form dense yellow precipitate:

Hg2+

+ 2NaOH HgO + 2Na+ + H2O

c) The State Pharmacopoeia of Ukraine additionally uses the following

reaction:

potassium iodide solution, being added dropwise gives a red precipitate that

dissolves in excess of reagent:

Hg2+

+ 2I‾ HgI2↓

HgI2 + 2KI K2[HgI4]

NITRATES

a) Powdered substance containing nitrates is added to a mixture of

nitrobenzene and sulphuric acid. After adding water, strong sodium hydroxide

solution and acetone the layer of organic solvent is coloured deep violet.

The State Pharmacopoeia of Ukraine additionally uses two other reactions.

b) Nitrates do not discolour potassium permanganate solution acidified with

dilute sulphuric acid (distinction from nitrites).

c) Nitrites in the reaction with phenazone in the presence of dilute hydrochloric

acid colour the solution green.

11

C6H

5

NNO

C6H

5

NNO

ONCH3

CH3

CH3

CH3

NaNO2

HCl

PHOSPHATES (ORTHOPHOSPHATES)

a) A yellow precipitate is formed in reaction of phosphates with silver nitrate

solution. This precipitate dissolves on addition of ammonia.

PO43-

+ 3AgNO3 Ag3PO4 + 3NO3-

Ag3PO4 + 6NH4OH → [Ag(NH3)2]3PO4 + 6H2O

b) A yellow colour develops after interaction with molybdovanadic reagent:

PO43-

+ HVO3 + 11H2MoO4 + 4NH4+ (NH4)4[PO4(MoO3)11VO3]+ 11H2O + H

+

POTASSIUM

a) After heating potassium salts with sodium carbonate solution no precipitate

is formed (distinction from alkaline-earth metals). Then to the hot solution sodium

sulphide solution is added, and no precipitate is formed (distinction from heavy

metals). After cooling in iced water and adding solution of tartaric acid a white,

crystalline precipitate is formed. COOH

CH OH

CH OH

COOH

COOK

CH OH

CH OH

COOH

+ K + + H +

b) A yellow or orange-yellow precipitate is formed after interaction with

sodium cobaltinitrite solution in the presence of dilute acetic acid:

2K+ + Na3[Co(NO2)6] K2Na[Co(NO2)6] + 2Na

+

c) This reaction is additionally used by the State Pharmacopoeia of Ukraine

Potassium salt put into the colourless flame makes it violet (the colour appears red

through an indigo prism).

SILVER

Silver salt solution forms a curdled, white precipitate after adding of

hydrochloric acid. Precipitate dissolves on addition of dilute ammonia.

Ag+ + HCl AgCl + H

+

AgCl + 2NH4OH [Ag(NH3)2]Cl + 2H2O

SODIUM

a) After heating sodium salts with potassium carbonate solution to boiling no

precipitate is formed (distinction from alkaline-earth metals). Adding of potassium

pyroantimonate solution and heating to boiling with following cooling yields a dense

white precipitate:

Na+ + K[Sb(OH)6] Na[Sb(OH)6] + K

+

b) A voluminous, white, crystalline precipitate is formed in the reaction with

methoxyphenylacetic reagent. After placing in water at 20°C and stirring for 5 min

12

the precipitate does not disappear, but it dissolves completely on adding of dilute

ammonia. After adding of dilute ammonium carbonate solution no precipitate is

formed.

Na+

N(CH3)

4

N(CH3)

4 CH

OCH3

COO

CH

OCH3

COONa

+ +

+

+-

c) Sodium salt, treated with hydrochloric acid and put into the colourless flame

makes it yellow.

SULPHATES

a) Barium chloride solution in the presence of dilute hydrochloric acid gives a

white precipitate:

SO42-

+ BaCl2 BaSO4 + 2Cl-

b) When to the suspension obtained during reaction (a) iodine solution is added

the suspension remains yellow (distinction from sulphites SO3- and dithionites S2O4

2-

), but is decolorized by adding dropwise stannous chloride solution (distinction from

iodates IO3-).

2I2 + 2SnCl2 → SnCl4 + SnI4

On boiling the mixture, no coloured precipitate is formed (distinction from

selenates SeO42-

and tungstates WO42-

).

SULPHITES

The State Pharmacopoeia of Ukraine, unlike European Pharmacopoeia, gives

two general reactions for sulphites identification.

a) To the prescribed solution containing sulphite ions dilute hydrochloric acid

is added. Gradually the solution gives off a gas with strong odour (sulphurous

dioxide).

SO32-

+ 2HCl SO2 + H2O + 2Cl-

b) After interacting with iodine the solution is decolourized:

SO32-

+ I2 + H2O SO42-

+ 2HI

ZINC

a) After adding of strong sodium hydroxide solution a white precipitate is

formed.

Zn2+

+2NaOH Zn(OH)2 + 2Na+

After adding of a further quantity of this solution the precipitate dissolves and

remains clear on addition of ammonium chloride solution.

Zn(OH)2 + 2NaOH Na2ZnO2 + 2H2O

After adding of sodium sulphide solution a flocculent white precipitate is

formed:

Zn2+

+ Na2S ZnS + 2Na+

b) Potassium ferrocyanide solution gives with zinc salts a white precipitate that

does not dissolve after adding of dilute hydrochloric acid:

Zn2+

+ 2K4[Fe(CN)6] K2Zn3[Fe(CN)6]2↓ + 6K+

13

Tests for purity

General questions on impurity determination

The very important part of the pharmacopoeial analysis is impurities

determination and limit tests.

Impurities are certain chemical substances, which can be present in small

amounts together with the main compound. Their presence in the preparation can be

explained either by the process of Preparation or by the storage.

During Preparation of the preparations, impurities can get into them from the

raw materials from which the substances are prepared, from the reagents, or from the

apparatuses. On the other hand, they can be the semi-products or side-products of

synthesis.

Among the impurities that get into the preparations from the apparatuses,

materials and reagents, we can meet inorganic ions – iron, magnesium, zinc, arsenic,

heavy metals; anions of the acids usually used for acidifying of the reaction mixture –

chlorides, sulphates, phosphates and so on. Such impurities are named non-specific

and their determination is the same in many preparations. That is why methods for

their determination are described in general part of the Pharmacopoeia as “Limit

tests”. In monographs, only preparation of the solution to be examined is noted. Other

impurities which can get into the preparation during their Preparation are

characteristic for only one preparation or group of preparations. These impurities are

named specific. It means that their determinations are described in the monographs.

Very often chromatographic methods (gas chromatography or high-pressure liquid

chromatography) are used for their determining. Sometimes simple chemical

reactions are used.

Impurities can get into the preparation during their storage too. For example,

some substances decompose when kept, particularly in presence of air and light. Such

impurities also can be divided into specific and non-specific. Non-specific impurities

can get into the preparation from the air. It may be, for example, ammonium salts.

These impurities also are determined according to general methods. Specific

impurities usually are the products of the different chemical processes going into the

preparations during the storage. In this case, the determination of impurities is carried

out by the method described in the monograph. Example of such impurities is acetic

acid in Aspirin.

A choice of the method for impurity determination depends of the processes of

medicines manufacture, the composition of the raw materials, the properties of the

substance and its behaviour during storage.

Impurities in the substances can be determined by chemical or physico-

chemical methods.

1. Chemical methods involve carrying out different chemical reactions with the

use of standard solutions or without them. Such general quantitative or limit tests are

laid down for a number of non-specific impurities. Limit tests use simple

comparisons of opalescence or colour with fixed standards. Standard solution is the

solution containing exact quantity of certain ion. For example, chloride standard

solution contains an exact quantity of sodium chloride in water solution. Usually

14

concentration of a standard solution is expressed in ppm and standard solutions of

one impurity with different concentrations are used for different preparations.

A choice of the reagent and the reaction for the determination is very

important. The analytical reaction chosen has to be sensitive in the certain test,

specific and reproducible.

Results of the reactions are compared colorimetrically or nephelometrically in

the solutions of the substance and in the standard solution after adding of

corresponding reagents. If result of the reaction in the solution examined (colour,

opalescence, or spot) is less than that in the standard we can say that amount of

impurity is less than in this standard solution.

2. Physico-chemical methods. Different chromatographic methods are often

used in the monographs (thin-layer chromatography, gas chromatography, liquid

chromatography, etc.) for impurities determination.

Clarity and degree of opalescence of liquids

This test is carried out by comparing the liquid to be examined with a reference

suspension or with the solvent.

A liquid is considered clear if its clarity is the same as that of water R or of the

solvent, or if its opalescence is not more pronounced than that of reference

suspension I.

There are reference suspensions I-IV, they should be freshly prepared from the

standard of opalescence and water R. Standard of opalescence is obtained by dilution

of primary opalescent suspension which in its turn is obtained by mixing up two

solutions: hydrazine sulphate solution and hexamethylenetetramine solution (they

give a white precipitate in a form of opalescent suspension).

The solutions should be compared using identical test tubes of colourless,

transparent, neutral glass with a flat base and an internal diameter of 15 mm to

25 mm, the depth of the layer being 40 mm, in diffused daylight 5 min after

preparation of the reference suspension, viewing vertically against a black

background.

Degree of coloration of liquids

The examination of the colour intensities of liquids in the range brown-yellow-

red is carried out by one of the two methods (I or II), which differ by the size of the

tubes, quantity of liquids and the way of viewing. Test is carried out using identical

tubes of colourless, transparent, neutral glass, in diffused daylight, looking against a

white background.

A solution is colourless if it has the appearance of water R or the solvent or is

not more intensely coloured than reference solution B9.

There are reference solutions of the scales B (brown, B1-B9), BY (brownish-

yellow, BY1-BY7), Y (yellow, Y1-Y7), GY (greenish-yellow, GY1-GY7), R (red, R1-

R9), and corresponding five standard solutions. Each reference solution is prepared

using prescribed volumes of a standard solution and hydrochloric acid 10g/l.

Standard solutions B, BY, Y, GY, R are prepared by mixing three primary

solutions: yellow (ferric chloride solution), red (cobalt chloride solution), and blue

15

(copper sulphate solution) in different proportions with hydrochloric acid 10g/l.

Primary solutions themselves are acidified with hydrochloric acid.

Method I: Liquids to be examined are compared in identical tubes of 12 mm

external diameter, taking volumes of 2 ml, viewing horizontally.

Method II: Liquids to be examined are compared in identical tubes with a flat

base and an internal diameter of 15 to 25 mm, the depth of the layer being 40 mm.

The comparison is made by looking vertically downwards through the columns of

liquid in the tubes.

Determination of pH

pH value of a solution gives the important information about purity and

identity of a preparation, because pH shows the presence of acidic or alkaline

impurities, and it is one of the chemical characteristics of a substance. Storage and

usage of solutions depend on their pH. Solutions for injections should have pH value

close to pH value of blood.

European Pharmacopoeia recommends using two methods for pH

determination: electrometric (potentiometric) and colorimetric, using indicators.

1. Potentiometric determination is used to measure the exact value of pH.

The potentiometric determination of pH is made by measuring the potential

difference between 2 appropriate electrodes immersed in the solution to be examined:

one of these electrodes is sensitive to hydrogen ions (usually a glass electrode) and

the other is the reference electrode (for example, a saturated calomel electrode), the

measuring apparatus is a voltmeter.

2. Colorimetric determination is made according to the table describing

relationship between reaction of solution, approximate pH and colour of certain

indicators.

Loss on drying and determination of water

These tests can be prescribed to control the quantity of water in the substance.

Loss on drying is the loss of mass expressed as per cent m/m. To check the

loss on drying the prescribed quantity of the substance should be placed in a

weighing bottle previously dried under the conditions prescribed. Then the substance

should be dried to constant mass or for the prescribed time over:

o diphosphorus pentoxide: “in a desiccator”, at atmospheric pressure or “in

vacuo” (pressure of 1.5 kPa to 2.5 kPa), or “under high vacuum” (at a pressure not

exceeding 0.1 kPa), at room temperature or within the temperature range prescribed

in the monograph;

o in an oven within a specified temperature range.

The term “dried to constant mass” means that two consecutive weighings do

not differ by more than 0.5 mg, the second weighing following an additional period

of drying.

16

Determination of water by distillation

Distillation of water is carried out with the help of toluene, which form

aseotropic mixture with water. After the distillation, when the water and toluene have

completely separated, the volume of water is read and calculation of the content of

water present in the substance as ml per kg is made. This method is widely used for

the analysis of medicinal plants preparations.

Semi-micro determination of water

The volumetric method of titration of water is based upon the quantitative

reaction of water with iodosulphurous reagent, being the mixture of sulphur dioxide

and iodine in an anhydrous medium of ethyleneglycol monomethyl ether in the

presence of a base – anhydrous pyridine.

SO2 + I2 + 2H2O H2SO4 + 2HI

The titration vessel is fitted with two platinum electrodes, a nitrogen inlet tube,

a stopper which accommodates the burette tip, and a vent-tube protected by a

desiccant. The substance to be examined is introduced through a side-arm which can

be closed by a ground stopper. Stirring is effected magnetically or by means of a

stream of dried nitrogen passed through the solution during the titration. The end-

point is determined by amperometry.

Pyridine reacts with hydroiodic acid and sulphur dioxide (reducing its

volatility).

N

H

I2

SO2

OH2 I

N

SOO

ON

+ + +3 + + +2

According to a monograph, either direct (by iodosulphurous reagent) or back

(excess of iodosulphurous reagent is titrated by anhydrous methanol) titration can be

used.

N

H

N

SOO

O

CH3OH CH

3SO

4++

+-

Individual determinations can be carried out successively if each component of

the test mixture is compatible with the other components and no other reactions take

place.

Micro determination of water

It is the coulometric titration of water, reactions which take place are similar to

the semi-micro determination of water. Iodine is produced electrochemically in the

reaction cell by oxidation of iodide. The iodine produced at the anode reacts

immediately with the water and the sulphur dioxide contained in the reaction cell.

The amount of water in the substance is directly proportional to the quantity of

17

electricity up until the titration end-point. When all of the water in the cell has been

consumed, the end-point is reached and thus an excess of iodine appears.

This method is used for the quantitative determination of small amounts of

water, a range of 10 µg up to 10 mg of water is recommended.

Limit tests

TEST FOR CHLORIDES

A solution of a substance is acidified with nitric acid, and this mixture as a

single addition is poured into the silver nitrate solution: HNO3

Cl- + AgNO3 AgCl + NO3

-

A white curdled precipitate or only opalescence (because a very small amount

of chlorides can be present) is formed. The opalescence is compared with the

opalescence produced by addition of a standard solution (containing a definite

quantity of sodium chloride and acidified with nitric acid) to the silver nitrate

solution.The liquids should be stirred and set aside protected from light for 5 minutes

before comparison, since the full opalescence is not developed immediately. After

standing for 5 min, any opalescence in the test solution should be not more intense

than that in the standard. The test-tubes should be compared laterally against a black

background.

Why the medium for this test is dilute nitric acid? If the medium is alkaline,

silver hydroxide (AgOH) may be formed. In this case we would obtain white

precipitate or opalescence even if there are no chlorides in the preparation. If the

medium is neutral the carbon dioxide presented in water would react with the silver

nitrate solution with the formation of white precipitate of Ag2CO

3. Nitric acid is

used for acidifying of the solution because another acids can form precipitates with

silver ions (for example, Ag2SO4).

TEST FOR SULPHATES

The sulphates impurity determination is based on the reaction with the barium

chloride by formation of white precipitate in the presence of acetic acid, which helps

to prevent precipitation of another anions of the second analytical group: CH3COOH

SO42-

+ BaCl2 BaSO4 + 2Cl-

In order to make this reaction more sensitive the reagent is prepared at first

from the solution of barium chloride and a small amount of sulphate standard solution

containing alcohol. Then solution to be examined and acetic acid are added to this

reagent. After 5 minutes the opalescence is compared with the opalescence produced

by addition of sulphate standard solution (containing a definite quantity of potassium

sulphate) and acetic acid to the above-mentioned mixture, containing barium

chloride. Any opalescence in the test solution should be not more intense than that in

the standard. Sensitivity of this test increases due to the presence of a small amount

of sulphate standard solution in each of the tubes, giving ionic concentrations which

18

exceed the solubility product of barium sulphate. The presence of alcohol helps to

prevent supersaturation.

TEST FOR AMMONIUM

Method A. This method is based on the reaction of ammonium with alkaline

potassium tetraiodomercurate solution (Nessler reagent):

NH2

I-Hg

I-Hg

NH3 + 2K2[HgI4] + KOH

+

I + 5KI + H2O-

The prescribed quantity of the substance to be examined is dissolved in water

in a test-tube, made alkaline if necessary by the addition of dilute sodium hydroxide

solution and mixed with alkaline potassium tetraiodomercurate solution. A standard

for comparison is prepared in the same manner, using ammonium standard solution

(containing a definite quantity of ammonium chloride) diluted with water, instead of

a solution of a substance. Both test tubes are stopped. After 5 min, any yellow colour

in the test solution should be not more intense than that in the standard.

Method B. To the prescribed quantity of the substance to be examined

dissolved or suspended in 1 ml of water heavy magnesium oxide is added. Then jar is

closed immediately after placing a wetted piece of silver manganese paper under the

polyethylene cap. It is allowed to stand at 40 °C for 30 min.

Heavy magnesium oxide makes medium alkaline and during the heating

ammonia is evolved. Then ammonia reacts with silver manganese paper (containing

silver nitrate and manganese sulphate):

2AgNO3 + MnSO4 + 4NH3 + 2H2O 2Ag + MnO2+ (NH4)2SO4 +

NH4NO3If the silver manganese paper shows a grey colour, it should be not more

intense than that of a paper prepared at the same time and in the same manner using

the ammonium standard solution instead of a solution (or suspension) of the

substance.

Methods C and D are described additionally by the State Pharmacopoeia of

Ukraine.

Method C. This method is used for the determination of ammonium impurity

in the preparations containing alkaline-earth and/or heavy metals. Sodium hydroxide

and sodium carbonate solutions are added to precipitate alkaline-earth and/or heavy

metals in the form of carbonates. After filtering the precipitates off, the reaction with

alkaline potassium tetraiodomercurate solution is carried out with the filtrate.

Method D. If the preparation contains ferric salts they should be bound in the

complex by adding of sodium-potassium tartrate solution in the presence of sodium

hydroxide solution. A complex is forming:

19

Apparatus for the limit test A

Dimensions in millimeters

CH CH C

O

COO

O

Fe

OO

-

Then the reaction with alkaline potassium tetraiodomercurate solution is

carried out.

TEST FOR ARSENIC

Pharmacopoeia describes two methods for arsenic impurity determination.

Method A is based on the reduction of arsenic compounds to gaseous

arsenious hydride, or arsine, by the use of zinc and dilute acid:

6Zn + As2O3 + 12HCl → 2AsH3+ 3H2O + 6 ZnCl2The solution is

previously treated with stannous chloride solution (reducing agent)

to convert compounds of arsenic (V) into compounds of arsenic

(III).

The apparatus for arsenic determination consists of a 100 ml

conical flask closed with a ground-glass stopper, through which

passes a glass tube. This tube is open at the upper end. The lower

end is drawn out to a diameter of 1 mm. There is a hole in the side

of this tube, 15 mm from the lower end. Such peculiarity in the

construction in made to remove condensed moisture from the

constricted part. The tube is loosely packed with lead acetate cotton

(or a small plug of cotton and a rolled piece of lead acetate paper).

Lead acetate reacts with hydrogen sulphide that could be possibly

emitted together with arsine from the sample, forming on the cotton

a precipitate of lead sulphide.

The upper end of the tube has a perfectly flat, ground surface.

Over the top of this tube a disc or a small square of mercuric

bromide paper is fixed (large enough to cover the orifice of the

tube), in such a way that gas evolved from the bottle passes through

a mercuric bromide paper. Pharmacopoeia suggests fixing this

paper using a second glass tube of the same diameter,

with a similar flat ground surface, placed in contact with

the first, and held in position by two spiral springs.

Arsine being formed reacts with mercury bromide on the paper, forming a stain,

intensity of colouration of which depends on the impurity concentration:

AsH3 + HgBr2 → AsH2(HgBr) + HBr

AsH3 + 2HgBr2 → AsH(HgBr)2 + 2HBr

AsH3 + 3HgBr2 → As(HgBr)3 + 3HBr

AsH3 + As(HgBr)3 → As2Hg3 + 3HBr

The solution to be examined is placed in the flask, hydrochloric acid, stannous

chloride solution and potassium iodide solution are added, and allowed to stand for

15 min. Then activated zinc is introduced, and two parts of the apparatus are

20

assembled immediately. The flask is immersed in a water bath at a temperature such

that a uniform evolution of gas is maintained. The reaction is allowed to go on for 2

hours. Standard is prepared in the same manner, using arsenic standard solution

(prepared by dissolving a definite quantity of arsenic trioxide in sodium hydroxide),

diluted with water. The mercuric bromide paper is then removed, and the stain is

compared with the standard stain.

The stain produced on the mercuric bromide paper in the test should be not

more intense than that in the standard.

Method B is based on the reduction of arsenic compounds by the use of

hypophosphorus reagent, in acidic medium. Hypophosphorus reagent, which is

solution of sodium hypophosphite and hydrochloric acid, reduces compounds of

arsenic (III) and (V) to a brown precipitate of free arsenic.

The substance to be examined is introduced into a test-tube containing

hydrochloric acid and potassium iodide and then mixed with 3 ml of hypophosphorus

reagent. Mixture is heated on a water-bath for 15 minutes and compared with a

standard, prepared in the same way, containing known quantity of arsenic standard

solution. Any colour in the test solution should be not more intense than that in the

standard.

NaH2PO2 + HCl NaCl + H3PO2

As2O3 + 3H3PO2 2As↓ + 3H3PO3

As2O5 +5H3PO2 2As↓ + 5H3PO3

The process of reduction has two stages, and phosphine can be considered a

real reducing agent:

2H3PO2 H3PO4 + PH3

As2O3 + PH3 2As↓ + H3PO3

This method can be also used for determination of selenium and tellurium

impurities, which are in the same way reduced to the free state. It is used often for the

arsenic determination in the preparations containing bismuth, mercury, silver and

antimony as far as sulphides and sulphites.

TEST FOR HEAVY METALS

Heavy metals are the metals with density equal or exceeding 5 g/cm3 (Pb, Cd,

Cu, Fe, Ni, Zn, Hg and others). They are the very undesirable impurities in medicinal

substances.

Method A. Concentrated solutions of heavy metals salts yield, on addition of

thioacetamide reagent in acidic medium, a black (or dark) precipitates of metal

sulphides. With very dilute solutions a brown coloration is produced. The intensity of

it varies according to the quantity of heavy metals present.

CH3

C

S

NH2

CH3COO NH

4+ + ++-2H2O H2S

Pb

2+ + H2S → PbS + 2H

+

Medium must be acidic to prevent the formation of the precipitates of metals

hydroxides and carbonates. The solutions are made acidic with buffer solution pH

21

3,5. Colouration in the test solution should be compared after 2 minutes with

colouration in a standard prepared by adding of buffer solution pH 3,5 and

thioacetamide reagent to lead standard solution (containing a definite quantity of lead

(II) nitrate). A blank should also be prepared, using a mixture of water and the

solution to be examined. Compared to the blank, the standard shows a slight brown

colour.

After 2 min, any brown colour in the test solution should be not more intense

than that in the standard.

Methods B-F describe especial conditions of sample Preparation but the main

conditions are the same.

TEST FOR CALCIUM

Reaction is based on the possibility of calcium-ions to form a white precipitate

with ammonium oxalate solution in the medium of dilute acetic acid.

CH3COOH

Ca2+

+ (NH4)2C2O4 CaC2O4 + 2NH4+

Dilute acetic acid and a solution of a substance is added to the previously

prepared mixture, containing a small amount of alcoholic calcium standard solution

(the principle of this is the same as in the test for sulphates, above) and the main

reagent, ammonium oxalate solution. After 15 minutes the opalescence is compared

with the opalescence produced by addition of aqueous calcium standard solution

(prepared by dissolving of known quantity of calcium carbonate in acetic acid, then

diluted with water) and dilute acetic acid to the mixture, containing ammonium

oxalate. Any opalescence in the test solution should be not more intense than that in

the standard.

We can’t choose the alkaline medium because of calcium hydroxide

precipitation. If the pH=7, calcium carbonate can form. The choice of acetic acid can

be explained by solubility of calcium oxalate in mineral acids.

TEST FOR MAGNESIUM

8-Hydroxyquinoline in the alkaline medium forms a yellowish-green complex

with the impurity at the presence of chloroform:

N

OH

Mg2+

N

O

N

OMg

H+CHCl

3+2 + 2

Magnesium is extracted from aqueous solution by the chloroform solution of

the main reagent, 8-hydroxyquinoline. The chloroform layer is then used for

comparison with the standard prepared in the same manner, using magnesium

standard solution, containing a definite quantity of magnesium sulphate. Any colour

in the solution obtained from the substance should be not more intense than that in

the standard.

22

TEST FOR MAGNESIUM AND ALKALINE-EARTH METALS

Magnesium and alkaline-earth metals (calcium, strontium, and barium) are

determined by the complexometric titration. Solution of the substance to be analysed

is added to the previously prepared alkaline solution, containing zinc sulphate,

mordant black 11 triturate, previously titrated by 0,01 M sodium edetate until the

violet colour changes to full blue (colour of free indicator).

N

O

NaO3S

O2N

N

OZn

OH2H

2O

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Zn

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

N

OH

NaO3S

O2N

N

OH

+

+

-2 H2O

NH4Cl

NH4OH

If the colour of the solution changes to violet (presence of the impurity), it is

titrated with 0,01 M sodium edetate until the full blue colour is again obtained.

N

O

NaO3S

O2N

N

Mg O

OH2

N

OH

NaO3S

O2N

N

OH

Mg2+

H+

H2O

+

-2

2 H2O

NH4Cl

NH4OH

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

N

O

NaO3S

O2N

N

Mg O

OH2

H2O

+

-2 H2O

NH4Cl

NH4OH

23

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Mg

N

OH

NaO3S

O2N

N

OH

+

The test is carried out in the presence of hydroxylamine hydrochloride and

ammonium chloride buffer solution pH 10,0 at the temperature 40 ºC. The volume of

0,01 M sodium edetate used in the second titration should not exceed the prescribed

quantity given in the monograph.

TEST FOR IRON

To a solution of the substance, solution of citric acid and 0,1 ml of thioglycollic

acid are added, and the solution is then made alkaline with ammonia and diluted with

water. A standard containing iron standard solution (prepared from ammonium iron

(III) sulphate by dissolving in the mixture of water and sulphuric acid) is prepared in

the same way, and the colours of the two solutions are compared after 5 minutes. Any

pink colour in the test solution should be not more intense than that in the standard.

Thioglycollic acid gives with iron salts in ammoniacal solution compounds, coloured

pink:

Fe3+

+ 2HS-CH2COOH + 5NH4OH → [Fe(OH)(S-CH2COO)2]2-

+ 5NH4+ + 4H2O

TEST FOR FLUORIDES

Impurity of fluorides is determined in the special apparatus. Substance to be

examined is placed into the inner tube of the apparatus together with acid-washed

sand and mixture of sulphuric acid and water. Mixture is heated using jacket of

boiling tetrachloroethane (146 ºC). Distillate is collected into a volumetric flask,

containing 0,1M sodium hydroxide and phenolphthalein. During the distillation

0,1 M sodium hydroxide could be added to the flask to ensure that the distillate

remains alkaline. When the distillation is over, solution in the volumetric flask is

diluted to the volume, and 20 ml of it is introduced into a glass-stoppered cylinder.

The same procedure is carried out with the fluoride standard solution instead of the

substance to be examined. Finally, equal volumes of aminomethylalizarindiacetic

reagent (red colour, contains cerous nitrate and aminomethylalizarindiacetic acid) are

introduced into the cylinders.

SiO2 + 6HF → H2[SiF6] + 2H2OH2[SiF6] + 2NaOH → Na2[SiF6] + 2H2O O

O

OH

OH

CH2 N

CH2

C

O

OH

CH2

C

O

OH

OH2

Ce(NO3)

3.

2

24

O

O

OH

O

CH2

O

CeO

H2O

H2O

N

CH2

CH2

C

O

C

O

Na2[SiF

6]

NaOH

O

O

ONa

ONa

CH2 N

CH2

C

O

CH2

C

O

O

O

Ce

H2O

H2O

F

Any blue colour in the test solution should be less intense than that in the

standard.

TEST FOR PHOSPHATES

Test for phosphates is carried out with sulphomolybdic reagent (solution of

ammonium molybdate and sulphuric acid) at the presence of stannous chloride

solution:

PO43-

+ 12(NH4)2MoO4 + 27H+ → H7[P(Mo2O7)6] + 24NH4

+ + 10 H2O

To compare blue colouration of the test solution and of a standard, prepared in

the same manner using phosphate standard solution (containing a known quantity of

potassium dihydrogen phosphate), volumes of 20 ml each are used, after 10 minutes.

Any yellow colour in the test solution should be not more intense than that in the

standard.

TEST FOR POTASSIUM

Freshly prepared solution of sodium tetraphenylborate gives with potassium a

white precipitate:

K+ + NaВ(C6H5)4 KB(C6H5)4 + Na

+

After 5 minutes, any opalescence in the test solution should be not more

intense than that in the standard, containing potassium standard solution (solution of a

known quantity of potassium sulphate) and the solution of sodium tetraphenylborate.

TEST FOR ALUMINIUM

Similar to the test for magnesium, solution of 8-hydroxyquinoline in

chloroform is used for the extraction of aluminium. This reagent gives fluorescent

complex with aluminium:

25

N

OH

Al3+

N

O

N

OAl

H+CHCl

3

N

O

+3 + 3

The intensity of the fluorescence of the test solution (I1), of the standard (I2)

and also of the blank (I3) is measured using fluorimeter (an excitant beam at 392 nm).

The fluorescence (I1–I3) of the test solution should be not greater than that of the

standard (I2–I3).

TEST FOR ZINC

Impurity of zinc is determined with the potassium ferrocyanide solution in the

presence of hydrochloric acid (according to the State Pharmacopoeia of Ukraine). In

the presence of zinc ions a white precipitate is forming:

HCl

3Zn2+

+ 2K4[Fe(CN)6] K2Zn3[Fe(CN)6]2 + 6K+

Acidic medium is used because zinc is amphotheric and in alkaline medium it

can be reformed into zincate ZnO22-

. If the substance to be examined contains

additionally the iron impurity (blue colour appears after adding of potassium

ferrocyanide solution) iron should be removed using dilute ammonia, in the form of

hydroxide that is filtered off. Then the filtrate is acidified (zincate is transformed into

Zn2+

) and the test is carried out.

After 10 min, any opalescence in the test solution should be not more intense

than that in the standard.

26

Chapter 2. MEDICINAL PREPARATIONS CONTAINING

THE ELEMENTS OF 7TH

AND 6TH

GROUPS OF

D.I. MENDELEYEV PERIODIC SYSTEM

Plan

1. Preparations of the halogens and hydrogen (hydrochloric acid,

concentrated).

2. Preparations of hypochlorous and hydrochloric acids’ salts (chlorinated

lime).

3. Preparations of the halides (sodium chloride, potassium chloride, sodium

bromide, potassium bromide, sodium iodide, potassium iodide).

4. Preparations of iodine (iodine, iodine solution in alcohol 5% and 10%,

iodinole).

5. Preparations of manganese (potassium permanganate).

6. Preparations of hydrogen peroxide (hydrogen peroxide solution 3 and 30

per cent, hydroperite, magnesium peroxide).

7. Preparations of sulphur (sodium thiosulphate, sodium sulphate decahydrate,

sulphur for external use).

Preparations of the halogens and hydrogen

Hydrochloric acid, concentrated, E.P.

(Acidum hydrochloricum concentratum)

HCl

Preparation

Pure hydrochloric acid is usually made by direct synthesis from hydrogen and

chlorine produced by electrolysis of sodium chloride solution:

NaCl Na+ + Cl

-.

Cathode: Anode:

H2O + ē → Ho + OH

- 2Cl

- − 2ē → 2Cl

o

Ho + H

o → H2 2Cl

o → Cl2

2NaCl + 2H2O Cl2 + H2 + 2NaOH

The chlorine is burned in hydrogen in large-diameter silica tubes.

H2 + C12 → 2HC1

The hydrogen chloride so formed is absorbed in water:

Properties

Pharmacopoeial preparation is a clear, colourless, fuming liquid, miscible with

water. It has a relative density of about 1.18.

Concentrated hydrochloric acid contains not less than 35 % and not more than

39% of hydrogen chloride. This acid fumes because hydrogen chloride combines

with ammonia (always present in the air) forming ammonium chloride (and it is

exactly the very minute particles of this compound that form the fume).

27

Identification

1. Diluted with water, the solution of the preparation is strongly acid. This

property is confirmed with correspondent indicator (E.P.).

2. Hydrochloric acid is recognized by the identification reactions for chlorides

(above) (E.P.).

3. It complies with the limits of the assay (E.P.).

4. After heating of HCl with manganese dioxide free chlorine evolves, being is

detected by its odour: to

4HCl + MnO2 Cl

2+ MnCl

2 + 2H

2O

Tests for purity

Free chlorine is detected by liberation of iodine from potassium iodide in the

presence of iodide-free starch solution. The iodine colours starch solution blue.

Cl2 + 2KI I

2 + 2KCl

Blue colour should disappear on the addition of 0.2 ml of 0.01 M sodium

thiosulphate solution.

Assay (quantitative determination)

1. Hydrochloric acid is assayed by titration with sodium hydroxide, using

methyl red as indicator (alkalimetry, s = 1) (E.P.).

HCl + NaOH NaCl + H2O

2. According to the density of hydrochloric acid, because a definite density

corresponds to a definite acid concentration.

Storage In an airtight container made of glass or another inert material, at a

temperature below 30 C.

Usage Concentrated hydrochloric acid is used for Preparation dilute

hydrochloric acid. The latter is administered orally to improve gastric acidity.

Preparations of hypochlorous and hydrochloric acids’ salts

Chlorinated lime (Calcaria chlorata)

CaOCl

Cl

Ca(OH)2 H

2O. . n

Chlorinated Lime is a mixed calcium salt of hypochlorous and hydrochloric

acids (calcium chloro-hypochlorite), associated with varying proportions of calcium

hydroxide and moisture.

Preparation

CaO + H2O Ca(OH)2

Ca(OH)2 + Cl2 CaOCl2 + H2O

28

Properties

Chlorinated lime is a dull white or light greyish powder with chlorine’s odour,

is partly solvable in water. It slowly decomposes on exposure to air due to the action

of atmospheric carbon dioxide and moisture.

Identification

1. Solution of chlorinated lime 1:10, added to the red litmus, colours it blue

(рН>7), the blue colour then disappears owing indicator’s destruction by chlorine:

CaOCl2 + H

2O Ca(OH)

2 + Cl

2

2. Under the effect of hydrochloric acid, chlorinated lime decomposes with the

evolution of free chlorine:

CaOCl2 + 2HCl → CaCl2 + Cl2 + H2O

After adding of potassium iodide solution the yellow colour of iodine appears:

Cl2 + 2KI I

2 + 2KCl

3. For the calcium identification the solution of ammonium oxalate is added

after chlorine evolved. The latter is reached by the boiling of the substance with

acetic acid. Acetic acid, like other acids, liberates chlorine from the chlorinated lime:

2CaOCl2 + 2CH3COOH → (CH3COO)2Ca + CaCl2 + Cl2↑ + H2O

(CH3COO)

2Ca + (NH

4)

2C

2O

4 CaC

2O

4+ 2CH

3COONH

4

Assay

Iodometric titration. For the assay, an aqueous suspension of the substance is

treated with acetic acid in the presence of excess of potassium iodide. The liberated

chlorine displaced an equivalent amount of iodine from potassium iodide. The iodine

produced in this way is titrated with sodium thiosulphate, using starch solution as

indicator (s = 1/2).

2CaOCl2 + 2HCl + 2KI → I2 + CaCl2+ 2KCl + H2O

I2 + 2Na2S2O3 2NaI + Na2S4O6

Chlorinated lime should contain not less than 32 % of available chlorine.

Storage In an airtight containers at cool, protected from light place.

Usage Disinfectant.

Preparations of the halides

Sodium chloride (Natrii chloridum), EP

NaCl

Potassium chloride (Kalii chloridum), EP

KCl

Preparation

Sodium chloride occurs widely in nature as massive underground deposits of

rock salt. This is exactly the main source for the production of the Preparation.

29

“Common salt” has been manufactured also for hundreds of years by evaporation of

seawater in shallow pans.

During the manufacture the brine obtained is purified in several stages. The

reagents for purification are barium chloride solution, sodium carbonate solution and

hydrochloric acid:

Na2SO4 + BaCl2 BaSO4 + 2NaCl

Na2HPO4 + BaCl2 BaHPO4 + 2NaCl

MgCl2 + Na2CO3 MgCO3 + 2NaCl

CaCl2 + Na2CO3 CaCO3 + 2NaCl

BaCl2 + Na2CO3 BaCO3 + 2NaCl

Na2CO3 + 2HCl 2NaCl + CO2 + H2O

The precipitates are filtered off after the adding of BaCl2, then after adding of

Na2CO3. Then the solution is purified by recrystallization.

Potassium chloride is made from carnallite, KCl·MgCl2·6H2O by a process of

fusion whereby the liquefied magnesium chloride hexahydrate can be separated from

the solid potassium chloride; or by a process of crystallization. It also can be prepared

from the silvinite KCl·NaCl.

Properties

Both the preparations are white, crystalline powders or colourless crystals (or

white pearls for NaCl). They are freely soluble in water, practically insoluble in

ethanol.

Identification is carried out using general identification reactions (EP) for

sodium, potassium and chlorides (above).

Tests for purity

Bromides. This impurity is determined with chloramine and sodium

thiosulphate in the presence of phenol red solution. The absorbance of the solution

measured at 590 nm is not greater than that of a standard prepared using solution of

potassium bromide. CH

3

SO2N

Cl

Na

CH3

SO2NH

2

+ 2HCl + Cl2 + NaCl

2Br - + Cl2 Br2 + 2 Cl -

Ferrocyanides (in sodium chloride). Ferrocyanides are detected by formation

of a blue precipitate (Prussian blue) after the adding of ferric ammonium sulphate in

sulphuric acid and ferrous sulphate solution. Blue colour should not develop within

10 min.

3Na4[Fe(CN)

6] + 4FeNH4(SO4)2 Fe4[Fe(CN)

6]3 + 6Na2SO4 + 2(NH4)2SO4

30

Iodides. In this test the crystalline substance is moistened by the acidified

mixture of sodium nitrite solution, being an oxidizing agent, and iodide-free starch

solution. An oxidizing agent liberates iodine from iodides, and blue colour is

producing. The substance should not show any blue colour.

2NaI + 2NaNO2 + 2H2SO4 I2 + 2NO + 2Na2SO4 + 2H2O

Barium. The test for barium is included to guard against the possible presence

of this impurity resulting from the use of barium chloride in process of purification

(see Preparation). The reagent is dilute sulphuric acid. After 2 h, any opalescence in

the solution should be not more intense than that in a mixture of solution S and

distilled water.

BaCl2 + H2SO4 BaSO4↓ + 2HCl

Potassium and sodium are pharmacological antagonists, that’s why impurity of

potassium is determined in sodium preparations and impurity of sodium is determined

in potassium preparations, by atomic emission spectrometry.

Assay

1. Argentometry (EP). A weighed quantity of substance is dissolved in water

and treated with a measured volume of 0,1 M silver nitrate determining the end-point

potentiometrically; s=1. Calculation is made with reference to the dried substance.

NaCl + AgNO3 AgCl + NaNO3

2. Back argentometry by Volhard in the presence of dibuthyl phthalate (EP).

A weighed quantity is dissolved in water, acidified with nitric acid, and treated

with an excess of silver nitrate solution in the presence of dibuthyl phthalate:

KCl + AgNO3 AgCl + KNO3

The excess of silver nitrate is then determined by titration with ammonium

thiocyanate, using ferric ammonium sulphate as indicator (s = 1).

Calculation is made with reference to the dried substance.

AgNO3 + NH4SCN AgSCN + NH4NO3

3NH4SCN + Fe(NH4)(SO4)2 [Fe(SCN)3] + 2(NH4)2SO4

3. Mercurimetric method. Standard solution is mercury nitrate, indicator is

diphenylcarbazone that forms red-violet complex with excessive amount of mercury

nitrate (s=2). Calculation is made with reference to the dried substance.

2NaCl + Hg(NO3)2 HgCl2 + NaNO3

CO

NH

N N

NH C6H

5

C6H

5

Hg(NO3)

2 CO

NH

N N

C6H

5

N

C6H

5

C O

NN

C6H

5

N

C6H

5

NH

Hg

HNO3

2 +

2_

The end-point can be also determined with sodium nitroprusside:

Na2[Fe(CN)5NO] + Hg(NO3)2 Hg[Fe(CN)5NO] +2NaNO3

Storage In airtight containers.

31

Usage The most important function of the sodium chloride is providing a

constant blood pressure. Isotonic (0,9%) sodium chloride solution is widely used as a

solvent for different injection solutions and as sodium chloride intravenous infusion.

Potassium chloride is used as antiarrythmic and the source of potassium ions.

Sodium bromide (Natrii bromidum), EP

NaBr

Potassium bromide (Kalii bromidum), EP

KBr

Preparation

Sodium and potassium bromides are manufactured from a bromide of iron,

FeBr2·2FeBr3, or Fe3Br8, which is produced by the action of bromine on moist iron

borings.

Fe + Br2 FeBr2

3FeBr2 + Br2 Fe3Br8 (FeBr2 . 2FeBr3)

Then this compound is boiled with the sodium or potassium carbonate solution

and filtered, and the filtrate is evaporated to dryness: t

о

Fe3Br8 + 4Na2CO3 + 4H2O 8NaBr + Fe(OH)2+ 2Fe(OH)3+ 4CO2

(K2CO3) (KBr)

The residue is then extracted with water and recrystallized.

Properties

Sodium bromide is a white, granular powder or small, colourless, transparent

or opaque crystals, slightly hygroscopic, freely soluble in water, soluble in alcohol.

Potassium chloride is a white, crystalline powder or colourless crystals, freely soluble

in water and in glycerol, slightly soluble in alcohol.

Identification is carried out using general identification reactions (EP) for

sodium, potassium and the reaction (a) for bromides with silver nitrate solution

(above).

There is one more non-pharmacopoeial reaction for bromides identification.

This is formation of a black precipitate when the copper sulphate (in the presence of

concentrated sulphuric acid) is added to the substance:

Cu2+

+ 2Br- CuBr2

This precipitate is destructed on addition of water.

Tests for purity

Bromates are determined by the interaction of bromate and bromide in the

presence of dilute sulphuric acid; with liberation of free bromine, which reacts with

potassium iodide in the presence of starch solution. Blue or violet colour should not

develop after 5 min.

BrO3- + 5Br

- + 6H

+ 3Br2 + 3H2O

Br2 + 2KI → I2 + 2KBr

32

Chlorides are determined by argentometric titration (Volhard method) after

boiling the solution with hydrogen peroxide concentrated solution in the presence of

dilute nitric acid. Bromides are more easily oxidized than chlorides, that is why

bromides are oxidized to bromine and only chlorides react with silver nitrate.

Iodides are determined by the adding of ferric chloride solution and the

coloration of chloroform layer. It should stay colourless.

2Fe3+

+ 2I- 2Fe

2+ + I2

Assay

Back argentometry by Volhard in the presence of dibuthyl phthalate (EP)

(s=1). Calculation is made with reference to the dried substance.

In calculating the result, a correction must be made to allow for the volume of

silver nitrate used in reacting with any chloride present (as determined by the test for

chloride):

The percentage content of NaBr is calculated from the expression:

a − 2,902 b

a = percentage content of NaBr and NaCl obtained in the assay and calculated

as NaBr; b = percentage content of Cl in the test for chlorides.

The percentage content of KBr is calculated from the expression:

a − 3,357 b

a = percentage content of KBr and KCl obtained in the assay and calculated as

KBr; b = percentage content of Cl in the test for chlorides.

The coefficients equal to the relations of molecular mass of the preparations to

the atomic mass of Cl.

Storage In airtight containers.

Usage The tranquillising preparations.

Sodium iodide (Natrii iodidum), EP

NaI

Potassium iodide (Kalii iodidum), EP

KI

Preparation

Sodium iodide and potassium iodide are prepared by processes exactly

analogous to those described for sodium (and potassium) bromide, but with iodine

instead of bromine.

Properties

Both preparations are white crystalline powders or colourless crystals. They are

very soluble in water, freely soluble in alcohol. Sodium iodide is deliquescent.

Identification is carried out using general identification reactions (E.P.) for

sodium, potassium and iodides (above).

33

Iodides can be also recognized by oxidation with the sodium nitrite solution:

2NaI + 2NaNO2 + 2H2SO4 I2 + 2NO + 2Na2SO4 + 2H2O

Ferric chloride solution can be also used as oxidizing agent:

2I- + 2Fe

3+ I2 + 2Fe

2+

Free iodine colours the chloroform layer violet.

Tests for purity

Iodates. The test for iodates is similar in principle to the test for bromate in

sodium bromide. To the solutions of preparations iodide-free starch solution and

dilute sulphuric acid are added. Blue colour should not develop.

IO3- + 5I

- + 6H

+ 3I2 + 3H2O

Thiosulphates are determined by the colour of the solution after adding of

starch solution and iodine. A blue colour should be produced.

I2 + 2Na2S2O3 2NaI + Na2S4O6

Assay

1. Iodatometry (EP). The solution is acidified with hydrochloric acid and

titrated with 0.05 M potassium iodate (until the colour changes from red to yellow).

This results first in liberation of iodine, but on further addition of iodate the iodine is

converted into iodine monochloride:

KIO3 + 5KI + 6HCl 3I2 + 6KCl + 3H2O

KIO3 + 2I2 + 6HCl 5ICl + KCl + 3H2O

Equation, which summarize the results of the reactions:

2KI + KIO3 + 6HCl 3ICl + 3KCl + 3H2O

To determine the end-point, the titration is continued, with vigorous shaking,

until most of the iodine has been converted into monochloride, as shown by the

decoloration of the added chloroform (s = 2). Calculation is made with reference to

the dried substance.

2. Argentometry (by Fajans). The solution of the substance is acidified with

acetic acid and then treated with 0,1 M silver nitrate using sodium eosinate as

indicator:

NaI + AgNO3 AgI + NaNO3

At the end-point the yellow precipitate of AgI colours pink due to the

adsorption of the indicator molecules on it (s = 1). Calculation is made with reference

to the dried substance.

3. Mercurymetric method (without indicator). The solution is titrated with

mercury nitrate solution (s = 4). At the end-point the red precipitate or mercury (II)

iodide is formed:

4KI + Hg(NO3)2 K2[HgI4] + 2KNO3

K2[HgI4] + Hg(NO3)2 2HgI2 + 2KNO3

Calculation is made with reference to the dried substance.

Storage Protected from light.

Usage Iodides are administered at the cases of a lack of iodine in the organism,

34

including endemic goitre. There are several preparations of eye drops, used for

treating of eye diseases (cataract etc.)

The preparations of iodine

Iodine (Iodum), EP

I2

Preparation

Iodine can be obtained from oil water or seaweeds (contain 0,5 % of iodine).

Professor Magidson O.Y. elaborated the process of iodine manufacturing from

oil water. This process consists of several stages:

1. Purification of oil water from the impurities of oil and naphthenic acids.

2. Oxidation of iodides containing in it into free iodine by sodium nitrite in the

presence of sulphuric acid:

2NaI + 2NaNO2 + 2H2SO4 I2 + NO + 2Na2SO4 + 2H2O

3. Adsorption of iodine by activated charcoal.

4. Desorption of iodine with the help of sodium hydroxide:

3I2 + 6NaOH 5NaI + NaIO3 + 3H2O

5. Subsequent oxidation of the iodides into free iodine by the action of

chlorine:

2NaI + Cl2 I2 + 2NaCl

6. Purification of iodine by the process of sublimation.

Properties

Iodine looks like greyish-violet, brittle plates or small crystals with a metallic

sheen. Preparation is very slightly soluble in water, soluble in alcohol, slightly

soluble in glycerol, very soluble in concentrated solutions of iodides. Solutions of

iodine in chloroform and carbon disulphide are violet (the same colour as iodine

vapour), solutions in water, alcohol, and aqueous iodides are reddish-brown.

Identification

1. A few fragments are heated in a test-tube. Violet vapour is evolved and a

bluish-black crystalline sublimate is formed (EP).

2. Iodine gives with starch solution a blue colour which disappears on warming

but reappears on cooling (EP). This is a very characteristic reaction of iodine.

Tests for purity

Bromides and chlorides. This test depends on the fact that silver iodide is

almost insoluble in dilute ammonia, but silver chloride is freely and silver bromide is

appreciably soluble, being reprecipitated on addition of excess of nitric acid.

Cl- + AgNO3 AgCl + NO3

-

AgCl + 2NH4OH [Ag(NH3)2]Cl + 2H2O

[Ag(NH3)2]Cl + 2HNO3 AgCl + 2NH4NO3

35

The solution obtained in this way is compared to the standard containing

0,01M hydrochloric acid mixed with water, dilute nitric acid and silver nitrate

solution.

Assay

A solution of the substance in aqueous potassium iodide is slightly acidified

with dilute acetic acid and titrated with 0,1M sodium thiosulphate, using starch

solution as indicator (s=1/2):

I2 + 2Na2S2O3 2NaI + Na2S4O6

Taking into consideration reaction of iodine with potassium iodide, the

equations can be represented as:

I2 + KI K[I3]

K[I3] + 2Na2S2O3 KI + 2NaI + Na2S4O6

Storage In airtight glass containers fitted with glass stoppers since the iodine

vapour attacks both cork and rubber.

Usage Antiseptic.

Iodine solution in alcohol 5% (Solutio Iodi spirituosa 5%)

Composition: Iodine – 5,0 g;

Potassium Iodide – 2,0 g;

Alcohol (96 %) – 41,0 g;

Purificated water to 100 g.

This solution contains 47,5 to 52,5 mg/ml of iodine, and 19,2 to 21,0 mg/ml of

potassium iodide.

Properties

A clear, reddish-brown liquid.

Identification

1. After adding of starch solution to the preparation blue-violet colour appear,

showing the presence of iodine.

2. Chloroform is added to the preparation till its decolouration (extraction of

iodine), then potassium is recognized with tartaric acid solution.

3. After the extraction of iodine (see 2) iodide identification is carried out using

the reaction (b) for iodides (above).

4. Iodine can be recognized by formation of iodoform, being the yellow

precipitate with characteristic odour:

C2H5OH + 4I2 + 6NaOH CHI3 + 5NaI + HCOONa + 5H2O

Assay

Quantity of iodine is determined by sodium thiosulphate titration using starch

solution as indicator; s =1/2:

I2 + 2Na2S2O3 2NaI + Na2S4O6

36

Quantity of potassium iodide is determined by Fajans method in the solution

obtained (s=1):

2NaI + KI + 3AgNO3 3AgI + KNO

3 + 2NaNO

3

Quantity of potassium iodide is calculated according to the formula:

analysisfor

OSNaAgNO

V

ТKVКVKI

100)(% 3223

Storage In an airtight amber bottles, protected from light.

Usage Antiseptic.

Iodine solution in alcohol 10% (Solutio Iodi spirituosa 10%)

Composition: Iodine – 100 g;

Alcohol (96 %) to 1 l.

This solution contains 9,5 to 10,5 % of iodine.

Properties

A clear, reddish-brown liquid.

Identification

See the identification (1) of iodine solution in alcohol 5%.

Tests for purity

Hydroiodic acid can form during the storage of the preparation:

I2 + C2H5OH → 2HI + CH3COH

This impurity is determined by the alkalimetric titration.

Assay As described under iodine (above).

Storage In an airtight amber bottles, protected from light. The preparation can

be stored for a month.

Usage Antiseptic.

Iodinole (Iodinolum)

Composition: Iodine – 1 g;

Potassium Iodide – 3 g;

Polyvinyl alcohol – 9 g;

Water to 1 l.

Iodinole is investigated as to the iodine solution in alcohol 5%.

37

Preparations of manganese

Potassium permanganate (Kalii permangаnas), EP

KMnO4

Preparation Manganese dioxide is fused with excess of potassium hydroxide in the

presence of a free supply of air. Then chlorine is passed through the solution:

2MnO4 +4KOH +O2 2K2MnO4 + 2H2O

2K2MnO4 + Cl2 2KMnO4 + 2KCl

Properties

A dark purple or brownish-black, granular powder or dark purple or almost

black crystals, usually having a metallic lustre, soluble in cold water, freely soluble in

boiling water. It decomposes on contact with certain organic substances.

Identification

1. After adding of dilute sodium hydroxide solution in the presence of alcohol a

green colour develops. After heating to boiling a dark brown precipitate is formed

(EP).

2KMnO4 + 3C2H5OH 2KOH + 2MnO2 + 3CH3CHO + 2H2O

2. After filtering the mixture obtained, the filtrate gives reaction of potassium

with sodium cobaltinitrite (EP, above).

3. After adding of hydrogen peroxide solution and dilute sulphuric acid to the

preparation it gets colourless:

2KMnO4 + 5H2O2 + 3H2SO4 2MnSO4 + K2SO4 + 5O2↑ + 8H2O

Assay

Iodometric titration after addition of potassium iodide, starch solution as

indicator (s=2/10 or 0,2):

2KMnO4 + 10KI +8H2SO4 2MnSO4 + 6K2SO4 + 5I2 + 8H2O

I2 + 2Na2S2O3 2NaI + Na2S4O6

Storage In an airtight container.

Usage Antiseptic.

Preparations of hydrogen peroxide

Hydrogen peroxide solution (3 per cent)

(Hydrogenii peroxydum 3 per centum)

Hydrogen peroxide solution (30 per cent)

(Hydrogenii peroxydum 30 per centum), EP

H2O2

38

Preparation

1. The part of hydrogen peroxide now produced is made by electrolytic

process. Sulphuric acid (40-68 %) is electrolyzed to give persulphuric acid; by

vacuum distillation (70-75C) this is hydrolyzed with formation of hydrogen

peroxide, which is removed as vapour.

H2SO

4 + HOH H

3O

+ + HSO

4

-

Cathode: Anode:

2H3O+ + 2e 2H2O 2HSO4

- - 2e 2HSO4

2H3O 2H2O + H2 2HSO4 H2S2O8

HOH

HOH

SO

O

OH

O

O

SO

OOH

H2O

2H

2SO

4+ + 2

2. Industrial manufacture of hydrogen peroxide is also carried out by air

autooxydation of alkylanthrahydroquinones (R = 2-ethyl, 2-tert-butyl, 2-penthyl): OH

OH

R

O

O

RO

2

H2O

2+

During the process the mixture of benzene with secondary alcohols is used,

hydrogen peroxide is extracted with water, distillated and rectificated.

Alkylanthraquinones formed in the process are reduced and used again.

Pharmacopeial preparation 3 % contains 2,5 to 3,5 per cent m/m of hydrogen

peroxide, yielding about 10 times its volume of oxygen on thermal decomposition.

Pharmacopeial preparation 30 % contains 29,0 to 31,0 per cent m/m of hydrogen

peroxide, yielding about 110 times its volume of oxygen on thermal decomposition.

Properties

Water solutions of hydrogen peroxide are colourless, clear liquids. Hydrogen

peroxide decomposes more or less rapidly in alkaline solutions, by the action of light

and heat, or under catalytic influences, particularly of iron, copper, or manganese

ions.

2H2O2 2H2O + O2↑

Stability of hydrogen peroxide is increased by addition of very small quantities

of inorganic or organic preservatives or stabilisers, such as sodium benzoate, boric

acid, urea etc.

Identification

1. After adding of dilute sulphuric acid and potassium permanganate solution

the solution becomes colourless or slightly pink (EP).

2KMnO4 + 5H2O2 + 3H2SO4 2MnSO4 + K2SO4 + 8H2O +5O2↑

39

2. The very characteristic and very delicate test for hydrogen peroxide consists

in adding ether and potassium chromate solution in the presence of dilute sulphuric

acid to the Preparation. A blue colour is being communicated to the ether on shaking.

The blue colour is due to perchromic acids formation (EP):

K2Cr2O7 + H2SO4 H2Cr2O7 + K2SO4

Cr OOH

O

O

Cr

O

O

OH H2O

2CrOH

O

O

O O Cr

O

O

OH H 2O

CrOH

O

O

O O Cr

O

O

OH H2O

2CrOH O O

O

O O

O

Cr OH

O O

O O

H 2O

+ +

+ 5 + 5

On staying the blue colour of ether layer gets green due to reduction Cr6+

Cr3+

.

3. It complies with the requirement for the content of H2O2 (EP).

Tests for purity

Test for acidity; organic stabilizers; and non-volatile residue.

Assay

Titration with potassium permanganate solution in the presence of dilute

sulphuric acid (EP) until a pink colour obtained (s=5/2 or 2,5).

5H2O2 + 2KMnO4 + 3H2SO4 2MnSO4 + K2SO4 + 8H2O +5O2

Storage Protected from light; if the solution does not contain a stabiliser, store

at a temperature below 15 °C. The label should state the name of the stabilizer.

Usage Antiseptic.

Hydroperite (Hydroperitum)

CONH

2

NH2

H2O

2.

Preparation

The preparation is obtained from the equal quantities of urea and hydrogen

peroxide. It is produced in tablets of white colour.

Properties

The citric acid solution 0,08 % is added as preservative. One tablet of

hydroperite is equivalent to 15 ml of hydrogen peroxide solution 3 %.

Identification

1. Urea in hydroperite solution is determined by the biuret test:

40

CONH

2

NH2

NH C O NH3

NH C OCONH

2

NH2

NH2

C

O

NH

C

O

NH2

O C

NH2

NH

C

NH

OHO C

NH2

NH

C

NH2

OKOH

Cu2+

O C

H2N

NH

C

N

OK

Cu

+

+

2

2. The presence of hydrogen peroxide is confirmed by perchromic acids

formation.

Assay

The same method as for the hydrogen peroxide solution. The preparation

contains 35% of hydrogen peroxide.

Storage Protected from light.

Usage Antiseptic.

Magnesium peroxide (Magnesii peroxydum)

(MgO2 + MgO)

Preparation

MgCl2 + 2KOH 2KCl + MgO + H2O

MgO + H2O2 MgO2 + H2O

Properties White odourless powder, practically insoluble in water, soluble in mineral

acids and boiling acetic acid. The preparation contains not less than 25,9 % of

magnesium peroxide.

Identification

1. Identification reaction for Mg2+

after dissolving the preparation in the

hydrochloric acid.

MgCl2 + Na2HPO4 + NH3 MgNH4PO4 + 2NaCl

2. Reaction of perchromic acids formation (above).

Assay

Permanganatometric titration (without indicator, s=5/2 or 2,5):

MgO2 + H2SO4 MgSO4 + H2O2

5H2O2 + 2KMnO4 +3H2SO4 2MnSO4 + K2SO4 + 8H2O + 5O2↑

Storage In an airtight container.

Usage Antacidic and disinfectant for the treatment of gastro-intestinal diseases.

41

Preparations of sulphur

Sodium thiosulphate (Natrii thiosulphas), EP

Na2S2O3 · 5H2O

Preparation

Oxidation of polisulphides:

2CaS2 + 3O2 2CaS2O3

CaS2O3 + Na2SO4 Na2S2O3 + CaSO4

Properties

Transparent, colourless crystals, efflorescent in dry air, very soluble in water,

practically insoluble in alcohol. It dissolves in its water of crystallisation at about 49

°C.

Identification

1. It decolourises iodinated potassium iodide solution (EP).

I2 + 2Na2S2O3 2NaI + Na2S4O6

2. After adding to the preparation of silver nitrate excess the white precipitate

is formed. It rapidly becomes yellowish, and then black (E.P.):

Na2S2O3 + 2AgNO3 Ag2S2O3 + 2NaNO3 (White)

Ag2S2O3 Ag2SO3 + S (Yellow)

Ag2SO3 + S + H2O Ag2S + H2SO4 (Black)

3. After adding to the preparation of water and hydrochloric acid a precipitate

of sulphur is formed and gas is evolved which gives a blue colour to starch iodate

paper (EP):

Na2S

2O

3 + 2HCl 2NaCl + SO

2 + S + H

2O

5SO2 + 2KIO3 → I2 + 4SO3 + K2SO4

4. Identification reaction (a) for sodium with potassium pyroantimonate (EP,

above).

Tests for purity

Sulphates and sulphites. After the adding of iodinated potassium iodide

solution to the substance sulphites are oxidized to sulphates. Then test for sulphates is

performed, using sulphates standard solution.

Sulphides are determined by reaction with sodium nitroprusside. The solution

should not become violet.

Na2S + Na2[Fe(CN)5NO] Na4[Fe(CN)5NOS]

Assay

Iodometric titration using starch solution as indicator, s=2:

I2 + 2Na2S2O3 2NaI + Na2S4O6

Storage In an airtight container.

42

Usage Detoxicant and desencibilisant as injections, sometimes as an external

insecticide.

Sodium sulphate decahydrate (Natrii sulphas decahydricus), EP

Na2SO4 10 H2O

Preparation

Anhydrous sodium sulphate is manufactured by heating sodium chloride with

concentrated sulphuric acid. The second stage requires a dull red heat:

NaCl + H2SO4 → NaHSO4 + HCl

NaCl + NaHSO4 → Na2SO4 + HCl

The decahydrate, which is also known as Glauber’s salt, is produced from

anhydrous sodium sulphate by crystallization from water.

Properties

White, crystalline powder or colourless, transparent crystals; freely soluble in

water, practically insoluble in alcohol. It partly dissolves in its own water of

crystallisation at about 33 °C.

Identification is carried out using general identification reactions (E.P.) for

sodium and sulphates (above). The substance should also comply with the test for

loss on drying (EP).

Assay

1. The substance is dissolved in water and titrated with 0,1M lead nitrate in the

presence of hydrochloric acid and methanol, determining the end-point

potentiometrically (EP). Calculation is made with reference to the dried substance

(s=1).

Na2SO4 + Pb(NO3)2 → PbSO4↓ + 2NaNO3

2. Gravimetric determination of sulphate by precipitation with barium chloride:

Na2SO4 + BaCl2 → BaSO4↓ + 2NaCl

Storage In an airtight container.

Usage Laxative preparation.

Sulphur for external use (Sulfur ad usum externum), EP

S

Preparation

The preparation is made by grinding of purificated sulphur (Sulphur

depuratum).

Properties

A yellow powder, practically insoluble in water, soluble in carbon disulphide,

slightly soluble in vegetable oils. The size of most of the particles is not greater than

43

20 µm and that of almost all the particles is not greater than 40 µm. It melts at about

120 °C.

Identification

1. Heated in the presence of air, it burns with a blue flame, emitting sulphur

dioxide which changes the colour of moistened blue litmus paper to red (EP).

S + O2 → SO2

SO2 + H2O → H+ + HSO3

-

2. The substance is oxidized with bromine water. The solution obtained gives

reaction (a) of sulphates with barium chloride (E.P., above).

3. The substance is dissolved in hot pyridine in the presence of sodium

hydrocarbonate. On boiling the solution, it colors bluish or green.

Assay

1. The oxygen-flask method (EP).

Sulphur is combusted to sulphuric acid (hydrogen peroxide solution is used as

an absorbent). The acid is titrated with 0,1M sodium hydroxide using phenolphthalein

solution as indicator. Blank titration is carried out (s=1/2).

S + O2 → SO2

SO2 + H2O2 → H2SO4

H2SO4 + NaOH → Na2SO4 + H2O

2. Alkalimetric back titration.

The substance is dissolved in standard potassium hydroxide alcohol solution:

12S + 6KOH → 2K2S5 + K2S2O3 + 3H2O

Then alcohol is distilled off, and the water and hydrogen peroxide concentrated

solution are added.

K2S5 + 8KOH + 16 H2O2 → 5K2SO4 + 20 H2O

K2S2O3 + 2KOH + 4H2O2 → 2K2SO4 + 4H2O

The equations can be summarize as:

S + 2KOH + 3H2O2 → K2SO4 + 4H2O

The excess of potassium hydroxide is titrated with hydrochloric acid solution,

using methyl orange as indicator. Blank titration is carried out (s=1/2).

KOH + HCl → KCl + H2O

Storage Protected from light.

Usage For the treatment of skin diseases, such as psoriasis, itch etc. Sometimes

it is used against intestinal worms.

44

Chapter 3. MEDICINAL PREPARATIONS CONTAINING

THE ELEMENTS OF 5TH

, 4TH

AND 3RD

GROUPS OF

D.I. MENDELEYEV PERIODIC SYSTEM

Plan

1. Preparations of nitrogen: (nitrous oxide, sodium nitrite, ammonia solution

concentrated).

2. Preparations of arsenic and bismuth: (arsenious trioxide for homoeopathic

preparations, bismuth subnitrate).

3. Preparations of carbon (activated charcoal, sodium hydrogen carbonate).

4. Preparations of boron and aluminium (boric acid, borax, aluminium oxide

hydrated).

Preparation of nitrogen

Nitrous oxide (Nitrogenii oxydum), EP

N2O

Preparation Nitrous oxide is produced from ammonium nitrate by thermic decomposition.

NH4NO3 t o

H2O + N2O 2

Then nitrous oxide is liquefied under 150 atmospheres pressure.

Properties Nitrous oxide is a colourless gas, heavier than the air, with a specific odour.

One part of nitrous oxide dissolves in about 1,5 volumes of water at 20 C and at a

pressure of 101 kPa.

Identification 1. Infrared absorption spectrophotometry, comparing with the reference

spectrum of nitrous oxide (EP).

2. Place a glowing splinter of wood in the substance to be examined. The

splinter bursts into flame (EP).

3. After introducing the substance into alkaline pyrogallol solution a brown

colour does not develop (EP).

4. After mixing of nitrous oxide with nitrogen oxide the red smoke doesn’t

appear (distinction from oxygen).

Tests for purity

Carbon dioxide, carbon monoxide, nitrogen monoxide, nitrogen dioxide, water.

Tests for purity are carried out by chromatographic methods.

Assay Method of gas chromatography (EP).

45

Storage Store liquefied under pressure in suitable containers (full metal

cylinders of grey colour). The taps and valves should not be greased or oiled.

Usage For inhalation as general anaesthetic in the mixture with oxygen (N2O –

80%, O2 – 20%).

Sodium nitrite (Natrii nitris), EP

NaNO2

Preparation Sodium nitrite is made by heating the sodium nitrate with metallic lead. The

product after cooling is extracted with water, and the solution is filtered from the

insoluble lead oxide and evaporated to crystallisation.

NaNO3 + Pb PbO + NaNO

2

Properties Colourless crystals or mass or yellowish rods, hygroscopic, freely soluble in

water, soluble in alcohol. Preparation is destructed on heating, or in the presence of

sand or glass:

3HNO2 HNO

3 + 2NO + H

2O

Identification

1. Formation of azodye (EP).

To the solution of the substance sulphanilic acid solution is added to form

diazonic salt. After adding of -naphthol solution and dilute sodium hydroxide

solution an intense red colour develops, showing the azodye formation.

NH2

SO3H

NaNO2

N+

N

SO3H

OH

NaOH

N

SO3H

N

NaO

Cl-

2. Identification reaction (b, EP) for sodium (above).

3. Identification reactions for nitrites:

a) the specific reaction for nitrite is formation of green-coloured product after

adding of phenazone and dilute sulphuric acid (EP):

C6H

5

NNO

C6H

5

NNO

ONCH3

CH3

CH3

CH3

NaNO2

HCl

46

b) nitrites discolour potassium permanganate solution acidified with dilute

sulphuric acid.

5NaNO2 + 2KMnO4 + 3H2SO4 2MnSO4 + K2SO4 + 5NaNO3 + 3H2O

c) on reacting with diphenylamine blue colour develops:

NH

NO2

H2SO

4 NN

HSO4

2+- H

+

-c.

d) The salt is decomposed by dilute acids with evolution of pale brown fumes,

due to the instability of the liberated nitrous acid:

2NaNO2 + H

2SO

4 NO

2 + NO + Na

2SO

4 + H

2O

Assay

1. Cerimetric back titration (EP).

A solution of the salt is run slowly into excess of 0,1M cerium sulphate. After

2 min (flask is stoppered) potassium iodide and starch solutions are added, and

titration with 0,1M sodium thiosulphate is performed. A blank titration is carried out,

calculation is made with reference to the dried substance; s=1/2.

NaNO2 + 2Ce(SO4)2 + H2O NaNO3 + Ce2(SO4)3 + H2SO4

2KI + 2Ce(SO4)2 I2 + Ce2(SO4)3 + K2SO4

I2 + 2Na2S2O3 2NaI + Na2S4O6

2. Back permanganatometric titration; using starch solution as an indicator. A

blank titration is carried out, calculation is made with reference to dried substance

(s=5/2 or 2,5).

5NaNO2 + 2KMnO4 + 3H2SO4 2MnSO4 + K2SO4 + 5NaNO3 + 3H2O

2KMnO4 + 10KI + 8H2SO4 5I2 + 6K2SO4 + 2MnSO4 + 8H2O

I2 + 2Na2S2O3 2NaI + Na2S4O6

Storage In an airtight container.

Usage Spasmolytic and antidote for cyanides.

Ammonia solution concentrated (Ammoniae solutio concentrata), EP

NH4OH

Properties Clear, colourless liquid, very caustic, miscible with water and with alcohol in

any proportions. Contains 25,0 to 30,0 per cent m/m of ammonia NH3.

Identification 1. Relative density is 0,892 to 0,910 (EP).

2. It is strongly alkaline (determined with indicator, EP).

47

3. Through the solution air is bubbled. The gaseous mixture obtained is leaded

over the surface of a solution containing hydrochloric acid and methyl red solution.

The colour changes from red to yellow.

NH3 + HCl NH4Cl

After adding of sodium cobaltinitrite solution a yellow precipitate is formed.

2NH4Cl + Na3[Co(NO2)6] (NH4)2Na[Co(NO2)6] + 2NaCl

Assay

Back acidimetric titration or neutralization method. The measured volume of

the preparation is added to the weighed flask containing excess of hydrochloric acid,

which is then reweighed. The excess of the acid is titrated with 0,1M sodium

hydroxide using methyl red as indicator (s=1, EP).

NH4OH + HCl NH4Cl + H2O

HCl + NaOH NaCl + H2O

Storage Store protected from air, at a temperature not exceeding 20 °C.

Usage For faint and collapse, a person is given to inhale the vapour of the

solution.

Preparations of arsenic and bismuth

Arsenious trioxide for homoeopathic preparations

(Arsenii trioxidum ad praeparationes homoeopathicae), EP

As2O3

Preparation The preparation is manufactured by burning of orpiment As2S3, or arsenical

iron pyrites FeAsS in the current of air:

2As2S3 + 9O2 2As2O3 + 6SO2

2FeAsS + 5O2 As2O3 + 2SO2 + Fe2O3

Properties White or almost white powder, practically insoluble to sparingly soluble in

water. It dissolves in solutions of alkali hydroxides and carbonates, with formation of

the corresponding meta-arsenites, e.g.:

As2O3 + 2NaOH 2NaAsO2 + H2O

As2O3 + Na2CO3 2NaAsO2 + CO2

It dissolves also in concentrated hydrochloric acid (exhibiting weak basic

properties):

As2O3 + 6HCl 2AsCl3 + H2O

Identification 1. Sodium sulphide solution, added to a solution of the preparation in dilute

hydrochloric acid, gives a yellow precipitate, which is soluble in dilute ammonia

(EP).

48

As2O3 + 6HCl 2AsCl3 + 3H2O

2AsCl3 + 3Na2S As2S3+ 6NaCl

2. Hypophosphorous reagent, added to a solution of the preparation in dilute

hydrochloric acid and heated on a water-bath, gives a black precipitate (EP):

As2O3 + 6HCl 2AsCl3 + 3H2O

NaH2PO2 + HCl H3PO2 + NaCl

2AsCl3 + 3H3PO2 + 3H2O 2As + 3H3PO3 + 6HCl

3. After adding to the solution of the preparation silver nitrate solution a yellow

precipitate is formed. It dissolves on addition of nitric acid and ammonia.

Na3AsO3 + 3AgNO3 Ag3AsO3 + 3NaNO3

Assay

1. Iodometric titration (EP).

The substance is dissolved in dilute sodium hydroxide solution. Then the

mixture is neutralized with dilute hydrochloric acid, and sodium hydrogen carbonate

is added (for interaction with hydroiodic acid). The solution is titrated with iodine

using starch solution as indicator; s=1/2.

As2O3 + 2I2 + 2H2O As2O5 + 4HI

HI + NaHCO3 NaI + CO2 + H2O

2. Direct bromatometric titration using methyl red is an indicator. At the end-

point indicator gets colourless due to its oxidation; s=3/2 or 1,5.

3As2O3 + 2KBrO3 3As2O5 + 2KBr

5KBr + KBrO3 + 6HCl 3Br2 + 6KCl + 3H2O

Storage In an airtight container.

Usage In homoeopathic preparations, sometimes in stomatology.

Bismuth subnitrate, heavy (Bismuthi subnitras, ponderosum), EP

4[BiNO3(OH)2], BiO(OH)

Bismuth subnitrate is a basic salt of variable composition:

Bi OH

OH

NO3

BiO

OHBi

O

NO3

BiONO

3

BiOOH

, ,,

Preparation Bismuth ochre Bi2O3 is heated with charcoal to give metallic bismuth. Then

metallic bismuth is dissolved in nitric acid.

Bi2O3 + 3C 2Bi + 3CO

Bi + 4HNO3 Bi(NO3)3 + NO + 2H2O

49

Bi

NO3

NO3

NO3

- HNO3

Bi

NO3

NO3

OH - HNO3

BiO

NO3

- HNO3

Bi OH

OH

NO3

- HNO3

BiO

OH

H2O

H2O

Properties This is a white powder, practically insoluble in water and in alcohol. It

dissolves in mineral acids with decomposition.

Wet with water powder makes blue litmus paper red (pH7).

BiONO

3

BiOOH

BiO

OH+ H2O HNO3 + 2

Identification 1. Potassium iodide, added to a solution of the preparation, gives a black

precipitate of bismuth iodide, soluble in excess of precipitant to form an orange

solution containing potassium iodobismuthite (EP).

Bi(NO3)3 + 3KI BiI3 + 3KNO3

BiI3 + KI K[BiI4]

2. Solutions of bismuth salts acidified with nitric acid give a yellowish-orange

colour with thiourea (EP):

Bi3 3(NH2)2CS [Bi((NH2)2CS)3]

3

3. Nitrates are determined according to general identification reactions (EP,

above).

4. The pH of the solution of the preparation should be measured (EP).

5. After heating of the preparation yellow-brown fumes and bright yellow

precipitate are formed:

Bi O BiOOH

NO3

Bi2O

3 NO O2

H 2O+ + +

t 0

2 2 1/22

Assay

Complexonometric titration (EP). The substance is dissolved in a mixture of

perchloric acid and water and titrated with 0,1M sodium edetate, using xylenol

orange triturate as indicator; s=1.

Bi3+

SO3Na

CH3

OH

CH2

CH3

O

CH2

N

CH2COONa

CH2COONa

N

NaOOCH2C

NaOOCH2C 3Na +-

+

(or Na3Ind)

BiInd

HClO4

50

Bi3+

CH2

CH2

N

N

CH2COO

CH2COO

CH2COO

CH2COONa

Bi

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

H+

Na+

+ + 2+

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

CH2

CH2

N

N

CH2COO

CH2COO

CH2COO

CH2COONa

Bi

H

+

Na+

Ind3-

+ +BiInd

2

_

_

The percentage of Bi is calculated, with reference to the dried substance.

Storage In an airtight container.

Usage Antiseptic, for the treatment of certain gastro-intestinal diseases.

Preparations of carbon

Charcoal, activated (Carbo activatus), EP

C

Preparation

Activated charcoal is obtained from vegetable matter by suitable carbonisation

processes intended to confer a high adsorption power. This preparation is usually

obtained by a dry distillation of foliar trees without air presence. For more adsorb

properties medicinal charcoal is steamed at 180C. During this process the resinous

substances are removed. The best charcoal’s brands are obtained by treating with zinc

chloride, magnesium chloride, sodium hydroxide or phosphoric acid solutions with

the following heating to 300-400C. Then charcoal is carefully purified by washing,

and dried.

In the preparation there are micropores (we can see them in microscope, their

diameter is 10-1

to 10-3

cm) and ultrapores (we can’t see them in microscope, their

diameter is about 9,2.10-7

cm). Ultrapores are essential for the process of adsorption.

The general pores surface of 1 g of activated charcoal is about 103 m

2.

Properties

A black, light powder free from grittiness, practically insoluble in all usual

solvents.

Identification

1. When heated to redness it burns slowly without a flame (EP).

51

2. It complies with the test for adsorption power (EP).

Tests for purity

Adsorption power. Adsorption of phenazone by the weighed quantity of

charcoal, mixed with water is measured. After shaking for 15 min the quantity of

phenazone that has not been absorbed is determined by bromatometric titration, using

methyl red as indicator. Blank titration is carried out.

Not less than 40 g of phenazone is adsorbed per 100 g of activated charcoal,

calculated with reference to the dried substance.

The adsorption power of preparation can also be determined with the

methylene blue.

Since activated charcoal is usually used at high dosage Pharmacopoeia

demands high purity of this Preparation. The preparation can’t contain sulphides

(determined using hydrochloric acid and lead acetate paper).

The quantities of copper, lead and zinc are determined by atomic absorption

spectrometry.

Storage Store in an airtight container.

Usage Preparation is used at different intoxications.

Sodium hydrogen carbonate (Natrii hydrocarbonas), EP

NaHCO3

Preparation Sodium hydrogen carbonate is manufactured by the ammonia-soda process (or

method by Solve). Strong brine containing a high concentration of ammonia is passed

through a “carbonating tower” where it is saturated with carbon dioxide under

pressure. The ammonia and carbon dioxide react to form ammonium bicarbonate, and

this, undergoing decomposition with the sodium chloride, causes the precipitation of

sodium bicarbonate, which is not very soluble in water. The reactions are reversible,

but the greater part of the sodium chloride is eventually converted into sodium

bicarbonate. Then it is separated by filtration.

NH3 + CO2 + H2O NH4HCO3

NH4HCO3 + NaCl NH4Cl + NaHCO3

Properties

Preparation is a white crystalline powder. Preparation is soluble in water,

practically insoluble in alcohol. When heated in the dry state or in solution, it

gradually changes into sodium carbonate.

Identification

It is carried out using general identification reactions (EP) for sodium,

carbonates and bicarbonates (above).

After adding of phenolphthalein to the water solution of the preparation a pale

pink colour is produced. After heating gas is evolved, and the solution becomes red

(EP).

52

NaHCO3 + H2O NaOH + CO2 + H2O

Tests for purity

Appearance of solution, carbonates, chlorides, sulphates, ammonium, arsenic,

calcium, iron, and heavy metals. The test for carbonates requires that a 5% w/v

solution shall have a pH not greater than 8,6.

Assay

Acidimetric titration, using methyl orange as indicator (EP, s=1):

NaHCO3 + HCl NaCl + CO2 + H2O

Storage In an airtight container.

Usage Antacidic.

Preparations of boron and aluminium

Boric acid (Acidum boricum), EP

H3BO3

Preparation

1. Boric acid is produced by decomposing of crude borax or tincal, Na2B4O7

10H2O, of kernite, Na2B4O7 4H2O with sulphuric acid. Mixture of concentrated

sulphuric acid and water is added to a boiling solution of borax in water.

Na2B4O7 10H2O + H2SO4 4H3BO3 + Na2SO4 + 5H2O

The hot liquid is filtered and set aside to crystallize. The boric acid is then

filtered off, washed until free from sulphate, and allowed to dry at ordinary

temperatures.

2. Boric acid can be also manufactured from asharite: 110 °C

B2O3 2MgO + 2H2SO4 → 2MgSO4 + 2H3BO3

Properties This is a white, crystalline powder, colourless, shiny plates greasy to the touch,

or white crystals, soluble in water and in alcohol, freely soluble in boiling water and

in glycerol (85 per cent). When heated, boric (orthoboric) acid loses water in three

stages: 100 C

H3BO3 HBO2 + H2O metaboric acid

160 C

4HBO2 H2B4O7 + H2O pyroboric acid

red heat

H2B4O7 2B2O3 + H2O boron trioxide

53

Identification 1. Boric acid (also in the form of a salt) can be detected by mixing the

substance with concentrated sulphuric acid in a porcelain dish, adding methanol (or

ethanol), and igniting. The flame has a green border, owing to formation of a volatile

methyl (or ethyl) borate (EP).

H3BO3 + 3CH3OH 3H2O + B

OCH3

OCH3

OCH3

2. Water solutions have acidic reaction (determined with indicator, EP).

3. Curcuma paper colours pink or brown-red:

B OH

OH

OH- OH

2

CH OHCHC

CH

OH

OCH3

CH OHCHCO

OCH3

CH OHCHC

CH

O

OCH3

B

O CH OHCHC

OCH3

OH

OH

+

After wetting with ammonia the colour gets green-black.

Assay

Alkalimetric titration in the presence of mannitol; using phenolphthalein as

indicator (EP).

The object of the mannitol is to form a mannitylboric acid which is a strong

enough to give a good end-point. Determination can be carried out in the presence of

another polyhydric alcohols, e.g. glucose, glycerol; s = 1.

H2C

C

C

C

C

C OHH2

HO

HO

OH

OH

OH

H

H

H

H

2 + B OHHO

HO

H

H

H

H

H

H

B

OH

OH

HO

O

O

CH2

C

C

CH

CH

CH2

O

O

OH

HO

HO

H2 OHC

C

C

C

C

H2C HO-

H+ + NaOH

-

B

OH

OH

HO

O

O

CH2

C

C

CH

CH

CH2

O

O

OH

HO

HO

H2 OHC

C

C

C

C

H2C HO

H

H

H

H

H

H

Na+ + H2O

Storage In an airtight container.

Usage External antiseptic (water or alcohol solutions, or ointment).

54

Borax (Borax), EP

Na2B4O7 1OH2O

Preparation

Preparation is obtained from native calcium borate by a process involving

decomposition with hot sodium carbonate solution. Calcium carbonate is filtered off

and cold solution is set aside for crystallization of sodium tetraborate.

CaB4O7 + Na2CO3 Na2B4O7 + CaCO3

Properties

A white, crystalline powder, colourless crystals or crystalline masses,

efflorescent, soluble in water, very soluble in boiling water, freely soluble in glycerol.

Identification 1. See identification of boric acid (EP, above).

2. After adding phenolphthalein solution into the solution of preparation it is

red (alkaline medium). On the addition of glycerol (85 per cent) the colour disappears

(solution becomes acidic, E.P.).

3. Sodium is determined using general identification reactions (EP) for sodium

(above).

Assay

1. Alkalimetric titration of mannitol neutralised solutions using

phenolphthalein as an indicator; (EP, s=1/2):

Na2B

4O

7

CH2OH

CH OH

COH H

CH OH

C OHH

CH2OH

CH2OH

CH O

CH O

COH H

C HOH

CH2OH

B

CH2OH

C HO

C HO

C OHH

CH OH

CH2OH

CH2OH

CH O

CH O

COH H

C HOH

CH2OH

B

CH2OH

C HO

C HO

C OHH

CH OH

CH2OH

+ 4 2Na+

+ 2H+

Na2B4O7 + 7H2O 4H3BO3 + 2NaOH

H2C

C

C

OH

OH

OH

H

H2

+ H3BO3

CH2

CH

CH2

HO

HO

HO H2

H

H2C

C

C

OH

O

OB

O

O

HO

CH2

CH

CH2

-

H+ NaOH

-H2C

C

C

OH

O

OB

O

O

HO

CH2

CH

CH2

H

H2

Na+

55

CH2OH

CH O

CH O

COH H

C HOH

CH2OH

B

CH2OH

C HO

C HO

C OHH

CH OH

CH2OH

CH2OH

CH O

CH O

COH H

C HOH

CH2OH

B

CH2OH

C HO

C HO

C OHH

CH OH

CH2OH

2H+

+ 2NaOH 2Na+

2. Acidimetric titration, using methyl orange as indicator (s=1/2):

Na2B

4O

7 + 2HCl + 5H

2O 4H

3BO

3 + 2NaCl

Storage In an airtight container.

Usage Antiseptic.

Preparations of aluminium

Aluminium oxide hydrated (Aluminii oxydum hydricum), EP

Al(OH)3

Preparation

Al2(SO

4)

3 + 6NH

4OH 2Al(OH)

3 + (NH

4)

2SO

4 60 ºC

or 2KAl(SO4)

2 + 6NH4OH 2Al(OH)

3 + K

2SO

4 + 3(NH

4)

2SO

4

alum

Properties

A white, amorphous powder, practically insoluble in water. The preparation

dissolves in dilute mineral acids and in solutions of alkali hydroxides.

Identification 1. Aluminium is determined using general identification reactions (EP) for

aluminium (above).

2. After roasting of the preparation with cobalt nitrate solution cobalt aluminate

(cobalt blue) is formed:

2Al(OH)3 Al2O3 + 3H2O

2Co(NO3)2 2CoO +4NO2 + O2

Al2O3 + CoO Co(AlO2)2

Assay

1 Complexometric back titration of aluminium (EP, s=1/2).

An excess of sodium edetate is added to the neutral solution of the preparation

(prepared using HCl and NH4OH), then it is titrated with 0,1 M zinc sulphate, using

solution of dithizone in ethanol as indicator (colour changes from greenish-blue to

reddish-violet); medium of ammonium acetate and dilute acetic acid. Calculation is

made for Al2O3.

56

Al3+

CH2

CH2

N

N

CH2COO

CH2COO

CH2COO

CH2COONa

AlCH

2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

H+

Na+

+

-

+

2

CH3COOH

CH3COONH4

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Zn+ ZnSO4

CH3COOH

CH3COONH4

- H2SO4

NN

NHNH

CS

NN

Zn

NN

CSZnSO4+

- H2SO4

CH3COOH

CH3COONH4

2. Gravimetric method. The substance is roasted to give aluminium oxide.

Storage In an airtight container, at a temperature below 30ºC.

Usage Antacidic.

57

Chapter 4. MEDICINAL PREPARATIONS CONTAINING THE

ELEMENTS OF 2ND

GROUP OF

D.I. MENDELEYEV PERIODIC SYSTEM

Plan

1. Preparations of magnesium (light and heavy magnesium oxides,

magnesium sulphate heptahydrate, light and heavy magnesium carbonates).

2. Preparations of calcium (calcium chlorides: dihydrate and hexahydrate).

3. Preparation of barium (barium sulphate).

4. Preparations of zinc (zinc oxide, zinc sulphate heptahydrate).

5. Preparations of mercury (mercuric chloride, mercury oxide, mercury

oxicyanide).

Preparations of magnesium

Magnesium is widely distributed, the most important native sources are the

minerals dolomite (MgCO3.CaCO

3); magnesite (MgCO

3), talc (3MgO.4SiO

2.H

2O),

and carnallite (MgCl2KCl6H2O). The magnesium salts are also found in seawater

and waters of many mineral springs.

Magnesium oxide, light (Magnesii oxydum leve)

Magnesium oxide, heavy (Magnesii oxydum ponderosum), EP

MgO

Preparation Magnesium oxide (light) is produced by heating of magnesium light carbonate

at 250о-350

оС until carbon dioxide is no longer evolved:

3MgCO3 . Mg(OH)

2 . 3H

2O 4MgO + 3CO

2 + 4H

2O

Properties Magnesium oxide is fine, white, amorphous powder, practically insoluble in

water. It dissolves in dilute acids with at most slight effervescence.

Identification 1. 15 g of magnesium oxides has an apparent volume before settling of about

150 ml (light oxide) or 30 ml (heavy oxide) (EP).

2. Preparation is identified after dissolving in nitric acid with following

neutralisation with sodium hydroxide (EP):

MgO + 2HNO3 Mg(NO3)2 + H2O

Mg2+

+ 2OH- Mg(OH)2

Mg(OH)2 + 2NH4+ Mg

2+ + 2NH4OH

Mg2+

+ Na2HPO4 + NH4OH MgNH4PO4 + 2Na+ + H2O

3. It complies with the test for loss on ignition (EP).

58

4. For the identification of magnesium-ion we can also use 8-

hydroxyquinoline, which forms in ammonia-ammonia chloride medium a yellow-

green crystalline precipitate. After adding of organic solvents (chloroform,

butylamine) the organic layer colours yellow-green (see also test for magnesium):

N

OH

Mg2+

N

O

N

OMg

H+NH

4OH

NH4Cl

+2 + 2

Assay

1. Complexometric titration (after dissolving in dilute hydrochloric acid) using

mordant black 11 triturate as indicator. Titrate is 0.1 M sodium edetate solution,

medium is ammonium chloride buffer solution pH 10.0. Mixture is heated to 40 °C

and then titrated until the colour changes from violet to full blue, EP; s =1.

N

O

NaO3S

O2N

N

OMg

H 2O

N

OH

NaO3S

O2N

N

OH

Mg2+

OH2

H+

(or [MgInd] H2O) 2.

+

2-

(or H2Ind)

H2O

NH4OH

NH4Cl

2

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Mg

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

Mg2+

H+NH

4OH

NH4Cl

++ 2

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

MgInd

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

NH4OH

NH4Cl

+ + H2[MgInd] H2O 2.

_ 2 H2O

2. Method of neutralisation. The preparation is dissolved in excess of 1 М

hydrochloric acid, which then is titrated with 1 М sodium hydroxide at the presence

of methyl orange (s=1/2):

MgO + 2HCl MgCl2 + H2O

59

HCl + NaOH NaCl + H2O

Storage Preparation should be stored in an airtight container, because

magnesium oxide can react with atmospheric carbon dioxide and water, with the

formation of magnesium carbonate and hydroxide respectively:

MgO + CO2 MgCO3↓

MgO + H2O Mg(OH)2↓

Usage Antacidic.

Magnesium sulphate heptahydrate (Magnesii sulfas heptahydricus), EP

MgSO4 · 7H2O

Preparation Preparation is manufactured by the action of sulphuric acid on magnesite:

MgCO3 + H2SO4 MgSO4 + CO2 + H2O

The liquid is filtrated and filtrate is evaporated to crystallisation. The excess of

sulphuric acid is taken to avoid hydrolysis of magnesium sulphate and formation of

basic salts, e.g. Mg(OH)OSO3H.

Properties Preparation is a white, crystalline powder or brilliant, colourless crystals, freely

soluble in water, very soluble in boiling water, practically insoluble in alcohol,

effloresce slightly in warm air.

Identification Identification is carried out using general identification reactions (EP) for

magnesium and sulphates (above).

Assay

Complexometric titration (see magnesium oxide, light) The calculation is made

with reference to the dried substance (s = 1, EP).

Storage In an airtight container.

Usage Prescribed as sedative, spasmolytic, analgesic, anticonvulsant, tocolytic,

for the treatment of hypertension and eclampsia (intramuscular, intravenous

injections); as antidote when poisoning of heavy metals, arsenic, tetraethyl lead,

soluble barium salts. Prescribed orally, it has holagogic and laxative action.

Magnesium carbonate, light (Magnesii subcarbonas levis), EP

Magnesium carbonate, heavy (Magnesii subcarbonas ponderosus), EP

Hydrated basic magnesium carbonate

3MgCO3 · Mg(OH)2 · 3H2O

60

Preparation

4MgSO4 + 4Na2CO3 + 4H2O 3MgCO3 Mg(OH)2 3H2O + 4Na2SO4 +

CO2

To prepare magnesium carbonate heavy, magnesium sulphate and sodium

carbonate are dissolved separately in boiling water. The solutions are mixed and

evaporated to dryness, and the residue is digested with boiling water. The insoluble

carbonate is then separated, washed until free from sulphate and dried.

To prepare magnesium carbonate light, cold solutions of magnesium sulphate

and sodium carbonate are mixed and boiled for 15 min, and the precipitate of

magnesium carbonate is then separated, washed until free from sulphate, and dried.

Properties Preparations are white powders, practically insoluble in water. They dissolve in

dilute acids with strong effervescence.

Identification 1. 15 g of magnesium carbonate has an apparent volume before settling of

about 180 ml (light carbonate) or 30 ml (heavy carbonate) (EP).

2. Identification is carried out using general identification reactions (EP) for

magnesium (after dissolving in dilute nitric acid and neutralizing with dilute sodium

hydroxide solution) and carbonates (above).

Assay

Complexometric titration (see Magnesium oxide, light) after dissolving

preparation in a mixture of water and dilute hydrochloric acid (s = 1, EP). The

content is calculated as MgO.

Storage In an airtight container.

Usage Astringent and antacidic.

Preparations of calcium

Calcium occurs in nature as CaCO3, in such minerals as chalk, marble,

limestone, and associated with MgCO3 in dolomite. CaSO4 occurs as gypsum (CaSO4

2H2O); the fluoride, CaF2, occurs as fluorspar. Bones contain a high percentage of

calcium phosphate.

Calcium chloride dihydrate (Calcii chloridum dihydricum), EP

CaCl2 2H2O

Calcium chloride hexahydrate (Calcii chloridum hexahydricum), EP

CaCl2 6H2O

61

Preparation Calcium chloride usually is prepared by the dissolving of calcium carbonate in

slight excess of hot hydrochloric acid, filtering when the reaction is complete, and

evaporating to a syrup which crystallizes when cooled.

CaCO3 + 2HCl CaCl2 + H2O + CO2

Impurities of magnesium and ferrous salts, which can be presented in certain

minerals, in the process of Preparation change into chlorides MgCl2 and FeCl2.

Solution obtained is saturated with gaseous chlorine (FeCl2 is oxidized into FeCl3),

and then an excess of calcium hydroxide is added:

2FeCl3 + 3Ca(OH)2 2Fe(OH)3 + 3CaCl2

MgCl2 + Ca(OH)2 Mg(OH)2 + CaCl2

During this process the concentration of calcium chloride increases. Excess of

calcium hydroxide is modified into calcium chloride with hydrochloric acid:

Ca(OH)2 + 2HCl CaCl2 +2H2O

Properties White, crystalline mass or colourless crystals, very soluble in water, freely

soluble in alcohol. Preparations freeze at about 29C. The crystals deliquesce in moist

air, effloresce in dry air, and melt in their water of crystallization at about 34C.

Identification

1. Identification is carried out using general identification reactions (EP) for

calcium and chlorides (above).

2. The preparations comply with the limits of the assay (EP).

Assay

1. Complexometric titration using calconecarboxylic acid triturate as

indicator

(s = 1, EP):

N N

OHHOOC OH

SO3HCa N N

ONaOOC O

SO3Na

Ca

H 2O OH

2

NaOH

H+

2 H2O

(or [CaInd] 2 H2O).

2+ +

2_

(or H2Ind)

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Ca

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

Ca2+

H+NaOH

++ 2

62

Titrate is 0,1M sodium edetate, medium is strong sodium hydroxide solution.

Solution is titrated until the colour changes from violet to full blue.

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Ca Ind

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

NaOH+ + H2

[CaInd] H2O 2._

2 H2O

2. Argentometry; s=1/2.

3. Mercurimetry; s=1.

Storage In an airtight container.

Usage Calcium chloride solution is prescribed for allergic diseases; it has

haemostatic and anti-inflammatory properties, and reduces the penetrability of blood

vessel wall. Calcium chloride is also a specific antidote for poisoning with

magnesium preparations; it is used for hypofunction of parathyroid glands. Calcium

chloride solution is prescribed as intravenous injections or orally (being injected

intramuscular, it causes necrosis).

Preparation of barium

From the barium salts only barium sulphate is used in medicine, because it is

not soluble either in water or in acids and alkalis (the soluble barium salts are toxic).

In nature barium occurs in form of sulphate – heavy spar or barytes (BaSO4) and

carbonate – witherite (BaCO3).

Barium sulphate (Barii sulfas), EP

BaSO4

Preparation

Soluble barium chloride is prepared from the minerals:

BaSO4 + 4C → BaS + 4CO↑

BaS + 2HCl →BaCl2 + H2S↑

BaCO3 + 2HCl → BaCl2 + H2O + CO2↑

Then the substance is prepared by precipitation from a solution of barium

chloride by addition of a soluble sulphate (or sulphuric acid):

BaCl2 + Na2SO4 BaSO4 + 2NaCl

To obtain fine dispersed barium sulphate solutions during precipitation should

be much diluted, and a protective colloid (e.g. linseed infusion) should be added.

Properties A fine, heavy, white powder, free from gritty particles, practically insoluble in

water and in organic solvents. It is very slightly soluble in acids and in solutions of

alkali hydroxides.

63

Identification 1. To identify barium sulphate it has to be transformed into soluble salts.

Preparation is heated with sodium carbonate solution: to

BaSO4 + Na2CO3 BaCO3 + Na2SO4

The precipitate is filtered off. The filtrate is acidified with dilute hydrochloric

acid and then used for the sulphate identification (above, EP).

2. The residue collected in the preceding test is washed with water, then treated

with dilute hydrochloric acid, and filtered. Then dilute sulphuric acid is added to the

filtrate to determine barium ion. A white precipitate of barium sulphate is insoluble in

dilute sodium hydroxide solution.

BaCO3 + 2HCl BaCl2 + H2O + CO2

BaCl2 + H2SO4 BaSO4 + 2HCl

Tests for purity

Barium sulphate is used internally in high dosage (50-100 g) therefore

pharmacopoeia gives strict requirements to the purity of the preparation:

tests for acidity or alkalinity, acid-soluble substances, oxidisable sulphur compounds,

soluble barium salts, phosphates, arsenic, heavy metals, loss on ignition; and

sedimentation.

Oxidisable sulphur compounds are determined using the reaction with

potassium iodide and potassium iodate solutions in the presence of starch solution.

5SO2 + 2KIO3 → I2 + 4SO3 + K2SO4

5KI + KIO3 3I2 + 3H2O + 6KCl

The blue colour of the solution should be more intense than that of a standard

prepared without potassium iodate.

In the test for soluble barium salts an acetic acid extract (solution S) after the

adding of dilute sulphuric acid is compared to the mixture of solution S and distilled

water.

In the sedimentation test, which controls the particle size, a weighed quantity

of the sample is shaken up with a measured volume of water in a measuring cylinder

of specified dimensions. The suspension is allowed to stand for 15 min, when the

process of settling must not have been below a defined mark.

Assay Is not required by Pharmacopoeia.

Storage In well-glued double paper packages (internal package is made of oil-

paper). It must be kept away from the carbonates to avoid barium carbonate

formation.

Usage For the X-rays diagnostics (roentgenology).

64

Preparations of zinc

Zinc is found in nature as minerals zinc blend ZnS; calamine ZnCO3. Usage of

zinc compounds in medicine is based on their possibility to form compounds with

proteins called albumates, which act as weak astringent and cauterizing agents.

Insoluble albuminates are used for treatment of wounds, forming protective film on

them. Zinc is a synergist of vitamins and promote their action.

Zinc oxide (Zinci oxydum), EP

ZnO

Preparation

1. Zinc oxide may be prepared by the heating of native zinc carbonate:

ZnCO3 ZnO + CO2

2. A solution of zinc sulphate is added to a boiling solution of sodium

carbonate. The precipitated basic carbonate of zinc is collected, washed until free

from sulphate, dried, and ignited; it then loses carbon dioxide and water, leaving the

oxide. to

5ZnSO4 + 5Na2CO3 + 3H2O 2ZnCO3 . 3Zn(OH)2 + 5Na2SO4 + 3CO2 to

2ZnCO3 . 3Zn(OH)

2 5ZnO + 2CO

2 + 3H

2O

Properties Zinc oxide is a soft, white or faintly yellowish-white, amorphous powder, free

from gritty particles, practically insoluble in water and in alcohol. It dissolves in

dilute mineral acids.

Identification 1. It becomes yellow when strongly heated; the yellow colour disappears on

cooling (EP).

2. Identification of zinc ions is carried out using general identification reactions

(EP, above).

3. Reaction of formation Reenman’s green. Zinc oxide is heated with cobalt

nitrate. Green colour is obtained.

ZnO + Co(NO3)2 CoZnO2 + 2NO2 + O

Assay

Complexometric titration (after dissolving preparation in dilute acetic acid)

using xylenol orange triturate as indicator; (s = 1, EP).

65

Zn2+

SO3Na

CH3

OH

CH2

CH3

O

CH2

N

CH2COONa

CH2COONa

Zn Ind

N

NaOOCH2C

NaOOCH2C 2Na +-

+

(CH2)6N4

(or Na2Ind)

Titrate is 0,1M sodium edetate, in the presence of hexamethylenetetramine.

Mixture is titrated until the violet-pink colour changes to yellow.

Zn2+

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Zn

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

H+

+ + 2

(CH2)6N4

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

ZnInd

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

Zn Ind

+ +

(CH2)6N4

H2

Storage Preparation should be stored in an airtight container, because it can

absorb atmospheric carbon dioxide and perform into zinc carbonate.

Usage Preparation is used externally in ointments, powders and other forms as

astringent, drying and disinfectant for skin diseases.

Zinc sulphate heptahydrate (Zinci sulfas heptahydricus), EP

ZnSO4 7H2O

Preparation

The substance is prepared by the action of diluted sulphuric acid on metallic

zinc or zinc oxide. Then the liquids are filtered and evaporated to crystallization. to

Zn + H2SO4 ZnSO4 + H2

ZnO + H2SO4 ZnSO4 + H2O

Properties

A white, crystalline powder or colourless, transparent crystals, efflorescent,

very soluble in water, practically insoluble in alcohol.

66

Identification 1.Identification is carried out using general identification reactions (EP) for

zinc and sulphates (above).

2. The preparation complies with the limits of the assay (EP).

Assay Complexometric titration (see zinc oxide). (s=1).

Storage In a non-metallic, airtight container.

Usage Preparation is used externally as antiseptic and astringent agent: eye

drops 0,1; 0,25; 0,5%; 0,25-0,5 % solutions for laryngology; 0,1-0,5 % solutions for

urology and gynaecology.

Preparations of mercury Most of the mercury compounds is prepared from the chief ore of mercury –

cinnabar, HgS.

Mercuric chloride (Hydrargyri dichloridum), EP

HgCl2

Preparation

1. Metallic mercury is dissolved in sulphuric acid and heated in the presence of

nitric acid. Then solution is evaporated to dryness, and the residue is mixed with

sodium chloride and manganese peroxide. The mixture is heated again, and mercury

dichloride sublime:

Hg + 2H2SO4 HgSO4 + 2H2O + SO2

HgSO4 + 2NaCl HgCl2 + Na2SO4

2. Preparation can be prepared by heating the mixture of mercury and chlorine

at 335-340 ºC. In this method mercurous chloride (Hg2Cl2) may be obtained as by-

product. To purify the preparation, it is sublimed and then crystallised from alcohol

or water, in which mercury monochloride does not dissolve.

Hg + Cl2 HgCl2

Properties A white, crystalline powder or colourless or white crystals or heavy crystalline

masses, soluble in water, in ether and in glycerol, freely soluble in alcohol.

Identification Identification is carried out using general identification reactions

(EP) for mercury and chlorides (above).

Tests for purity Mercurous chloride is determined by dissolving the

preparation in ether. The solution obtained should not show any opalescence.

Assay

1. Complexonometric titration by substitute. At first 0.1 M sodium edetate and

buffer solution pH 10.9 are added. Mercury ions form complexes with the titrate.

67

Hg

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Hg

22+

+ H++

pH 10,9

buffer

solution

Then mordant black triturate, used as indicator, is added, and the excess of

sodium edetate is titrated with 0.1 M zinc sulphate until the colour changes to purple

(first titration); (s = 1, EP).

ZnSO4

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Zn

H2SO

4+ +pH 10,9

buffer

solution

N

O

NaO3S

O2N

N

OZn

H 2O

N

OH

NaO3S

O2N

N

OH

OH2

H2SO

4

ZnSO4

+

2-

H2O2

buffer

solution

pH 10,9

Then potassium iodide is added to destroy complex Hg EDTA, and equivalent

to mercuric chloride quantity of sodium edetate is titrated with 0.1 M zinc sulphate

(second titration).

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Hg

K2[HgI

4]

buffer

solution

pH 10,9

+ 4KI + + 2K+

2H+

For the calculation volume of 0.1 M zinc sulphate used in the second titration

is taken. Calculation is made with reference to the dried substance.

2. Method based on the reduction of mercuric dichloride to free mercury,

which is determined by iodometric titration. Reducing agent is formaldehyde in

alkaline medium. Mercury formed is oxidised with an excess of 0,1 М iodine solution

at the presence of potassium iodide;(s =1):

HgCl2 + HCOH + 3KOH → Hg↓ + HCOOK + 2KCl + 2H2O

68

Hg + I2 HgI2

HgI2 + 2KI K2[HgI4]

Excess of iodine is titrated with sodium thiosulphate solution, using starch

solution as indicator:

I2 + 2Na2S2O3 2NaI + Na2S4O6

Storage In an airtight container.

Usage Preparation is used as antiseptic. It is very toxic and not used internally.

When mercury dichloride gets on skin, it also causes poisoning. Pills and solutions of

preparation are usually coloured with eosin to distinguish them from other

preparations (by bright pink colour). The preparation forms precipitates with proteins

and alkaloids, so strong tea and milk can be used as first aid for mercury poisoning.

Yellow mercuric oxide (Hydrargyri oxydum flavum)

HgO

Preparation It is prepared by precipitation, using solutions of mercuric chloride and sodium

hydroxide. The yellow precipitate is left to settle, washed by decantation, and then

washed on the filter until free from chloride. It is then allowed to dry at air

temperature.

HgCl2 + 2NaOH HgO + 2NaCl + H2O

The colour of the preparation varies from yellow to orange depending on the

temperatures at which it is precipitated, and is due to the size of the particles. The

process of Preparation can’t be carried out at high temperatures, because this give the

red oxide, which is not used in medicine. To obtain preparation free from by-products

(e.g. mercuric subchloride HgOHCl), solution of mercuric chloride is added to the

alkali solution.

Properties Yellow or orange-yellow, heavy, fine amorphous powder. Preparation darkens

slowly being exposed to light. Practically insoluble in water and alcohol, easy soluble

in dilute hydrochloric, nitric and acetic acids.

Identification After dissolving in hydrochloric acid identification is carried out with

potassium iodide solution, being added dropwise. In this case a red precipitate that

dissolves in excess of reagent is formed.

HgO + 2HCl HgCl2 + H2O

HgCl2 + 2KI HgI2↓ + 2KCl

HgI2↓ + 2KI K2[HgI4]

Tests for purity

Mercurous salts are discovered with hydrochloric acid:

Hg22+

+ 2Cl- Hg2Cl2 (white)

69

Assay

1. Indirect acidimetric titration. Mercuric oxide is weighed and dissolved in

water with excess of potassium iodide. Potassium hydroxide obtained is titrated with

hydrochloric acid solution at the presence of methyl red as indicator (s=1/2):

HgO + 4KI + H2O K2HgI4 + 2KOH

KOH + HCl KCl + H2O

2. Back alkalimetric titration (s=1/2).

HgO + 2HCl → HgCl2 + H2O

HCl + NaOH → NaCl + H2O

Storage In an airtight amber bottles.

Usage Preparation is used as external antiseptic in eye ointments. Very toxic!

Mercuric oxycyanide (Hydrargyri oxycyanidum)

HgO Hg(CN)2

Properties

White or slight yellowish powder, very slightly soluble in water. Water

solutions have alkaline reaction.

Identification Potassium iodide, ferrous sulphate, and ferric chloride solutions are added to

the solution of Preparation. After acidifying with hydrochloric acid red precipitate of

mercuric iodide, HgI2, appears. After adding more potassium iodide red precipitate

disappears, and a blue precipitate is formed (Prussian blue).

HgO Hg(CN)2 + 4KI + H2O 2HgI2↓ + 2KCN + 2KOH

HgI2↓ + 2KI K2[HgI4]

18KCN + 3FeSO4 + 4FeCl3 → Fe4[Fe(CN)6]3↓ + 3K2SO4 + 12 HCl

Assay

Mercury oxide is determined by direct acidimetry, using methyl orange as

indicator (s=1/2). NaCl

HgO + 2HCl HgCl2 + H2O

Preparation contains no less than 45% of HgO.

Then mercuric cyanide is assayed by indirect acidimetry (or acidimetry by

substituent). To the solution obtained potassium iodide is added, and solution is

titrated with 0,1M hydrochloric acid (s=1/2).

Hg(CN)2 + 4KI K2HgI4 + 2KCN

KCN + 2H2O 2HCN + 2KOH

2KOH + 2HCl 2KCl + 2H2O

Preparation contains no less than 53,3 % of Hg(CN)2.

Storage In an airtight amber bottles.

Usage Preparation is used as external antiseptic. Very toxic!

70

Chapter 5. MEDICINAL PREPARATIONS CONTAINING THE

ELEMENTS OF 1ST

AND 8TH

GROUPS OF

D.I. MENDELEYEV PERIODIC SYSTEM

Plan

1. Preparations of copper (copper sulphate pentahydrate).

2. Preparations of silver (silver nitrate and colloidal preparations of silver).

3. Preparations of iron (ferrous sulphate heptahydrate).

Preparation of copper In nature copper is found as copper pyrites, CuFeS2 (from which it is extracted

in metallurgy), cuprite, Cu2O, copper glance Cu2S, and malachite, CuCO3 Cu(OH)2.

Copper forms two series of compounds, the cuprous, derived from cuprous

hydroxide, CuOH, and the cupric, derived from cupric hydroxide, Cu(OH)2.

Copper sulphate pentahydrate (Cupri sulfas pentahydricus), EP

CuSO4 5H2O

Preparation Copper sulphate is prepared by the dissolving of metal copper in concentrated

sulphuric acid in the presence of nitric acid:

3Cu + 3H2SO4 + 2HNO3 3CuSO4 + 4H2O + 2NO

Solution obtained is evaporated (sulphuric acid, nitric acid and nitrogen oxide

are evolved) and CuSO4 . 5H

2O is crystallised from the solution.

Properties A blue, crystalline powder or transparent, blue crystals, freely soluble in water,

soluble in methanol, practically insoluble in alcohol.

Identification 1. Ammonia solution, added to a solution of a cupric salt, gives a blue

precipitate, which dissolves in excess of the precipitant to form a deep blue solution

(EP):

2CuSO4 + 2NH4OH (NH4)2SO4 + Cu2(OH)2SO4

Cu2(OH)2SO4 + 6NH4OH + (NH4)2SO4 2[Cu(NH3)4]SO4 + 8H2O

The colour is due to the presence of the cuprammonium cation, [Cu(NH3)4]+.

2. Water solution of copper sulphate (1:20) in reaction with metallic iron

covers it with thin red coating of metal copper:

CuSO4 + Fe FeSO4 + Cu

3. Solution of the preparation gives with sodium sulphide a black precipitate of

cupric sulphide, which dissolves in dilute nitric acid on boiling.

CuSO4 + Na2S CuS + Na2SO4 t

o

3CuS + 8HNO3 3Cu(NO3)2 + 3S + 2NO + 4H2O

71

4. Solution of copper sulphate, acidified with acetic acid, gives with potassium

ferrocyanide reddish-brown precipitate of copper ferrocyanide, soluble in ammonia.

2CuSO4 + K4[Fe(CN)6] Cu2[Fe(CN)6] + 2K2SO4

5. Reaction with polyalcohols and oxyacids (glycerol, gluconic acid, etc.) is

specific for cupric salts.

6. The solution of the preparation gives reaction (a) of sulphates (EP, above).

7. The preparation complies with the test for loss on drying (EP).

Assay

Iodometric titration after reducing Cu2+

to Cu+1

with potassium iodide in the

presence of sulphuric acid. Iodine is titrated with 0,1M sodium thiosulphate, using

starch solution (added towards the end of the titration) as indicator (s=1).

2CuSO4 + 4KI 2CuI +I2 + 2K2SO4

I2 +2Na2S2O3 2NaI + Na2S4O6

Storage In an airtight container.

Usage Water solution of the preparation is used as external antiseptic an

astringent, in the combined preparations of vitamines and minerals as source of

copper, sometimes it is used internally as emetic.

Preparations of silver Silver occurs in the free state, also as horn silver, AgCl, and as silver glance,

Ag2S. Silver forms only one series of compounds, in which the metal is univalent.

Silver nitrate (Argenti nitras), EP

AgNO3

Preparation Preparation is manufactured by the dissolving of copper-silver alloy in nitric

acid on heating: t

o

Ag Cu + 4HNO3 AgNO3 + Cu(NO3)2 + NO + 2H2O

Properties A white, crystalline powder or transparent, colourless crystals, very soluble in

water, soluble in alcohol.

Identification 1. Identification is carried out using general identification reactions (EP) for

silver and nitrates (above).

2. Silver can be recognized by the reaction of “silver mirror”:

AgNO3 + 2NH4OH [Ag(NH3)2]NO3 + 2H2O

[Ag(NH3)2]NO

3 R CO

H

H 2O Ag R C

O

ONH4

NH3 NH

4NO

32 + + 2 + + + 2

72

3. Diphenylamine gives a blue colouration with nitrates as far as with nitrites

(see sodium nitrite, above).

Tests for purity

Appearance of solution, acidity or alkalinity, foreign salts, aluminium, lead,

copper and bismuth.

Foreign salts are determined after precipitating of silver with dilute

hydrochloric acid and filtering the precipitate off. The filtrate is evaporated to dryness

and the residue is weighed.

The test for aluminium, lead, copper and bismuth consists in adding

concentrated ammonia to the solution of the Preparation. At first, it produces a dark

precipitate of Ag2O, but the precipitate dissolves in excess of ammonia, and the

solution should be then clear and colourless. Lead, bismuth and aluminium cause a

white turbidity due to precipitation of their hydroxides (which are not soluble in

excess of ammonia), and copper gives a blue solution due to the formation of

cuprammonium ion.

Assay

Thiocyanatometric titration after dissolving the preparation in water and

acidifying with dilute nitric acid, using ferric ammonium sulphate solution as

indicator until reddish-yellow colour is obtained (s = 1, EP).

AgNO3 + NH4SCN AgSCN + NH4NO3

3NH4SCN + FeNH4(SO4)2 Fe(SCN)3 + 2(NH4)2SO4

Storage As silver nitrate slowly decomposes in light, turning black, it should

be stored protected from light; in a non-metallic container.

Usage Silver nitrate solution is used as external antiseptic, for the

cauterizations.

Colloidal preparations of silver

Colloidal preparations of silver (collargol and protargol) contain metallic silver

in the colloidal state bound with peptides obtained from egg or milk proteins.

Collargol and protargol are used as external antiseptics, due to the presence of silver.

Collargol (Collargolum, Argentum colloidale)

Preparation

Colloidal preparations of silver are manufactured from egg protein or casein

(milk protein) and silver nitrate. Protein is steamed or treated with acids (or alkalies)

forming lisalbinic and protalbinic acids (or their salts, e.g. sodium salts), which have

reducing properties.

Silver nitrate is converted into silver oxide by the sodium hydroxide solution:

AgNO3 + NaOH → AgOH↓ + NaNO3

2AgOH → Ag2O↓ + H2O

73

Then silver oxide is purified and mixed with sodium lisalbinate and sodium

protalbinate solutions. As a result of reduction metallic silver is obtained and in the

colloidal state it forms coordination bonds with peptides.

Properties

Greenish or bluish-black plaites with a metallic sheen, soluble in water with

formation of a colloidal solution. Contains not less than 70 % of silver.

Identification

1. It is carbonized when heated, giving the characteristic odour of “burned

horn”.

2. The residue obtained in the reaction (1) is dissolved in nitric acid and

filtrated. Hydrochloric acid gives with the filtrate a white precipitate of silver

chloride:

AgNO3 + HCl → AgCl↓ + HNO3

3. Biuret test for identification of peptide part of preparation (see Hydroperite).

4. Reaction of distinction from protargol. Colloidal solution of the preparation

(1:50) on adding dilute hydrochloric acid gives brown precipitate. The precipitate

dissolves after addition of alkali, and the colloidal solution forms again.

Assay.

The preparation is weighed and carbonized by concentrated sulphuric acid and

nitric acids during 15 min. Then silver nitrate obtained is determined by

thiocyanatometric titration (see silver nitrate, s=1).

mlg

T

TAgNO

CSNNH

golcollarCSNNH /01541,0

70

10001079,0

70

1003

4

4

Storage In an airtight amber bottles, protected from light.

Usage Water solutions of the preparation are used as external antiseptics in the

forms of eye drops, ointments, solutions for irrigations of purulent wounds and

bladder.

Protargol (Protargolum)

Properties

Brownish-yellow powder, very soluble in water, practically insoluble in

alcohol and ether, hygroscopic. Contains not less than 7,8 % and not more than 8,3 %

of silver.

Preparation, identification, assay and storage See Collargol.

Usage Antiseptic, astringent, anti-inflammatory in the forms of 1-5 % solutions

(application on mucous membranes of upper parts of respiratory tract and in urology),

and 1-3 % eye drops. Solutions are prepared ex tempore.

74

Preparations of iron

Ores of iron are very widely distributed in nature and include haematite, Fe2O3,

limonite, 2Fe3O3 3H2O, magnetic iron ore, Fe3O4, and spathic iron ore, FeCO3. Iron

forms two series of salts, the ferrous salts (solutions are coloured very pale green),

derived from ferrous hydroxide, Fe(OH)2, and the ferric salts (solutions are coloured

yellow, brown, or red), derived from ferric hydroxide, Fe(OH)3.

Ferrous sulphate heptahydrate (Ferrosi sulfas heptahydricus), EP

FeSO4 ∙ 7H2O

Preparation

Ferrous sulphate is prepared by dissolving of an excess of metallic iron in 25-

30% sulphuric acid on heating at 80 C:

Fe + H2SO4 → FeSO4 + H2↑

Solution obtained is evaporated to dryness and dried at 30 C, because at 64 C

preparation melts in its own water of crystallization.

Properties

Light green, crystalline powder or bluish-green crystals, efflorescent in air,

freely soluble in water, very soluble in boiling water, practically insoluble in alcohol.

The pH of the solution is 3.0 to 4.0, owing to hydrolysis.

Identification

1. Identification is carried out using general identification reactions (EP) for

iron (reaction a) and sulphates (above).

2. The substance complies with the limits of the assay (EP).

3. Dimethylglyoxime gives with ferrous salts red complex.

Tests for purity

Appearance of solution, pH, chlorides, ferric ions, manganese, zinc and heavy

metals.

Ferric ions are determined by titration with 0,1M sodium thiosulphate after

interaction with potassium iodide (indicator is starch solution). EP states the limit of

the titrate.

2Fe3+

+ 2I‾ → 2Fe2+

+ I2

I2 + 2Na2S2O3 → 2NaI + Na2S4O6

Manganese compounds are determined by oxidation to red-coloured

permanganate ion MnO4- and comparing with the standard solution prepared using

0,02M potassium permanganate.

Assay

1. Cerimetric titration after dissolving the preparation in the previously

prepared mixture of sodium hydrogen carbonate, water and sulphuric acid. Titrate is

0,1M ammonium and cerium nitrate, indicator is ferroin. Solution is titrated until the

red colour disappears (s=1, EP).

3FeSO4+3(NH4)2Ce(NO3)6 → Fe2(SO4)3+Fe(NO3)3+3Ce(NO3)3+6NH4NO3

75

N

N

Fe

Ce4+

N

N

Fe

Ce3+

2 +

+

3 +

+

3 3

red green

2. Permanganatometric titration, without indicator. Titration is carried out until

pink coloration of the solution (s=10/2 or 5).

10FeSO4 + 2KMnO4 + 8H2SO4 → 5Fe2(SO4)3 + K2SO4 + 2MnSO4 + 8H2O

Storage In an airtight container.

Usage As a source of iron for iron-lacking anemia.

76

Chapter 6. RADIOPHARMACEUTICAL PREPARATIONS

(RADIOPHARMACEUTICA)

Radiopharmaceutical preparation is any medicinal product which, when ready

for use, contains one or more radionuclides (radioactive isotopes) included for a

medicinal purpose.

A nuclide is a species of atom characterised by the number of protons and

neutrons in its nucleus (and hence by its atomic number Z, and mass number A) and

also by its nuclear energy state. Isotopes of an element are nuclides with the same

atomic number but different mass numbers. Nuclides containing an unstable

arrangement of protons and neutrons will transform spontaneously to either a stable

or another unstable combination of protons and neutrons with a constant statistical

probability. Such nuclides are said to be radioactive and are called radionuclides. The

initial unstable nuclide is referred to as the parent radionuclide and the resulting

nuclide as the daughter nuclide.

The radioactive decay or transformation may involve the emission of charged

particles, electron capture (EC) or isomeric transition (IT). The charged particles

emitted from the nucleus may be alpha particles (helium nucleus of mass number 4)

or beta particles (negatively charged, generally called electrons or positively charged,

generally called positrons). The emission of charged particles from the nucleus may

be accompanied by the emission of gamma rays. Gamma rays are also emitted in the

process of isomeric transition.

The decay of a radionuclide is governed by the laws of probability with a

characteristic decay constant and follows an exponential law. The time in which a

given quantity of a radionuclide decays to half its initial value is termed the half-life

(T1/2).

The penetrating power of each radiation varies considerably according to its

nature and its energy. Alpha particles are completely absorbed in a thickness of a few

micrometers to some tens of micrometers of matter. Beta particles are completely

absorbed in a thickness of several millimetres to several centimetres of matter.

Gamma rays are not completely absorbed but only attenuated and a tenfold reduction

may require, for example, several centimetres of lead. For most absorbents, the

denser the absorbent, the shorter the range of alpha and beta particles and the greater

the attenuation of gamma rays.

Each radionuclide is characterised by an invariable half-life, expressed in units

of time and by the nature and energy of its radiation or radiations. The energy is

expressed in electronvolts (eV), kilo-electronvolts (keV) or mega-electronvolts

(MeV).

Generally the term “radioactivity” is used to describe the phenomenon of

radioactive decay and to express the physical quantity (activity) of this phenomenon.

The radioactivity of a preparation is the number of nuclear disintegrations or

transformations per unit time.

In the International System (SI), radioactivity is expressed in becquerel (Bq)

which is one nuclear transformation per second. Absolute radioactivity measurements

77

require a specialised laboratory but identification and measurement of radiation can

be carried out relatively by comparing with standardised preparations.

Identification of padiopharmaceutical preparation is carried out by comparing

the beta-ray spectrum or gamma-ray spectrum obtained of the preparation with that of

a standartizated radionuclide.

Identification is also carried out by examining the chromatogram obtained in

the test for radiochemical purity. The distribution of radioactivity should contribute

to the identification of the preparation.

Tests for purity in radiopharmaceutical preparations usually contain

radionuclidic purity and radiochemical purity.

Radionuclidic purity: the ratio, expressed as a percentage, of the radioactivity

of the radionuclide concerned to the total radioactivity of the radiopharmaceutical

preparation. The relevant radionuclidic impurities are listed with their limits in the

individual monographs.

The most generally useful method for examination of radionuclidic purity is

that of gamma spectrometry (for example, the gamma-ray spectrum does not

significantly differ from that of a standardised preparation). Due to differences in the

half-lives of the different radionuclides present in a radiopharmaceutical preparation,

the radionuclidic purity changes with time.

Radiochemical purity: the ratio, expressed as a percentage, of the radioactivity

of the radionuclide concerned which is present in the radiopharmaceutical preparation

in the stated chemical form, to the total radioactivity of that radionuclide present in

the radiopharmaceutical preparation. The relevant radiochemical impurities are listed

with their limits in the individual monographs.

The determination of radiochemical purity requires separation of the different

chemical substances containing the radionuclide and estimating the percentage of

radioactivity associated with the declared chemical substance. The monographs for

radiopharmaceutical products may include paper chromatography, thin-layer

chromatography, electrophoresis, gas chromatography and liquid chromatography.

Moreover certain precautions special to radioactivity must also be taken for radiation

protection.

Each monograph for radiopharmaceutical preparation has a part

“Radioactivity”.

Measurement of radioactivity.

The radioactivity of a preparation is stated at a given date and, if necessary,

time.

It is common to carry out the measurement with the aid of a primary standard

source. Primary standards may not be available for short-lived radionuclides e.g.

positron emitters. Ionisation chambers and Geiger-Müller counters may be used to

measure beta and beta/gamma emitters; scintillation or semiconductor counters or

ionisation chambers may be used for measuring gamma emitters; low-energy beta

emitters require a liquid-scintillation counter. For the detection and measurement of

alpha emitters, specialised equipment and techniques are required.

The radioactivity of a solution is expressed per unit volume to give the

radioactive concentration.

78

Storage Store in an airtight container in a place that is sufficiently shielded to

protect personnel from irradiation by primary or secondary emissions.

Radiopharmaceutical preparations are intended for use within a short time and

the end of the period of validity must be clearly stated.

Sodium phosphate 32

P injection

(Natrii phosphatis (32

P) solutio iniectabilis), EP

Preparation

Phosphorus-32 is a radioactive isotope of phosphorus and may be produced by

neutron irradiation of sulphur.

Properties

A clear, colourless solution.

Sodium phosphate (32

P) injection is a sterile solution of disodium and

monosodium (32

P) orthophosphates made isotonic by the addition of sodium chloride.

The injection contains not less than 90.0 per cent and not more than 110.0 per cent of

the declared phosphorus-32 radioactivity at the date and hour stated on the label. Not

less than 95 per cent of the radioactivity corresponds to phosphorus-32 in the form of

orthophosphate ion. The specific radioactivity is not less than 11.1 MBq of

phosphorus-32 per milligram of orthophosphate ion.

Phosphorus-32 has a half-life of 14.3 days and emits beta radiation.

Identification

1. The beta-ray spectrum or the beta-ray absorption curve does not differ

significantly from that of a standardised phosphorus-32 solution obtained under the

same conditions. The maximum energy of the beta radiation is 1.71 MeV (E.P.)

2. On the chromatogram obtained in the test for radiochemical purity, the

distribution of radioactivity contributes to the identification of the preparation (E.P.).

3. Zirconium nitrate in the concentrated nitric acid gives with the preparation a

white friable precipitate.

Usage Anti-tumour for the treatment of blood diseases and for the tumour

diagnostics.

Sodium iodohippurate (131

I) injection

(Natrii iodohippurati (131

I) solutio iniectabilis), EP

Preparation

Iodine-131 is a radioactive isotope of iodine and may be obtained by neutron

irradiation of tellurium or by extraction from uranium fission products.

Properties

A clear, colourless liquid.

Sodium iodohippurate (131

I) injection is a sterile solution of sodium 2-(2-

[131

I]iodobenzamido)acetate. It may contain a suitable buffer and a suitable

antimicrobial preservative such as benzyl alcohol. The injection contains not less than

90.0 per cent and not more than 110.0 per cent of the declared iodine-131

79

radioactivity at the date and hour stated on the label. Not less than 96 per cent of the

iodine-131 is in the form of sodium 2-iodohippurate. The specific radioactivity is

0.74 GBq to 7.4 GBq of iodine-131 per gram of sodium 2-iodohippurate.

Iodine-131 has a half-life of 8.04 days and emits beta and gamma radiation.

Identification

1. The gamma-ray spectrum does not differ significantly from that of a

standardised iodine-131 solution. The most prominent gamma photon of iodine-131

has an energy of 0.365 MeV (E.P.).

2. On the chromatograms obtained in the test for radiochemical purity, the

main peak of radioactivity in the chromatogram obtained with the test solution is

similar in position to the spot corresponding to 2-iodohippuric acid in the

chromatogram obtained with the reference solution (EP).

Usage For the kidney diseases diagnostics.

80

Chapter 7. GENERAL METHODS OF ANALYSIS

OF ORGANIC MEDICINAL SUBSTANCES

Plan

1. Classification of organic medicinal substances.

2. Determination of basic physical constants: (melting point, boiling point,

density, refractive index, specific optical rotation).

3. Bases of chemical analysis of organic substances: (element analysis, analysis

by functional groups).

Organic medicinal preparations are classified on:

1. Aliphatic:

• alkanes and their haloderivatives;

• alcohols;

• aldehydes;

• carbonic acids, oxy- and aminoacids;

• ethers and esters.

2. Cyclic:

• terpenoids;

• derivatives of cyclopropane, derivatives of adamantane.

3. Aromatic;

• phenols;

• aromatic amines and the acyl-derivatives;

• oxy- and aminoacids of aromatic origin;

• derivatives of aromatic sulphoacids.

4. Heterocyclic:

• are classified according to the structure of their heterocycles.

5. Biologically active natural compounds;

• alkaloids;

• glycosides;

• hormones;

• vitamins;

• antibiotics.

The general methods of analysis of organic medicinal substances include

determination of their physical constants.

Determination of melting point

Melting point is very important physical constant for organic medicinal

substances, which is used for their identification (in pure condition or as derivatives:

oximes, amides, hydrazones and etc.).

The melting point is a temperature, at which a hard phase of substance is in

equilibrium with fusion.

There are three methods for determining of melting point (according to State

Pharmacopoeia of Ukraine).

I. Melting point – capillary method.

81

The melting point determined by the capillary method is the temperature at

which the last solid particle of a compact column of a substance in a tube passes into

the liquid phase.

When prescribed in the monograph, the same apparatus and method are used

for the determination of other factors, such as meniscus formation or melting range,

that characterise the melting behaviour of a substance.

Apparatus. The apparatus consists of:

—a suitable glass vessel containing a liquid bath (for example, water, liquid

paraffin or silicone oil) and fitted with a suitable means of heating,

—a suitable means of stirring, ensuring uniformity of temperature within the

bath,

—a suitable thermometer with graduation at not more than 0.5 °C intervals and

provided with an immersion mark. The range of the thermometer is not more than

100 °C,

—alkali-free hard-glass capillary tubes of internal diameter 0.9 mm to 1.1 mm

with a wall 0.10 mm to 0.15 mm thick and sealed at one end.

Method. Unless otherwise prescribed, dry the finely powdered substance in

vacuo and over anhydrous silica gelR for 24 h. Introduce a sufficient quantity into a

capillary tube to give a compact column 4 mm to 6 mm in height. Raise the

temperature of the bath to about 10 C below the presumed melting point and then

adjust the rate of heating to about 1 C per minute. When the temperature is 5 °C

below the presumed melting point, correctly introduce the capillary tube into the

instrument. For the apparatus described above, immerse the capillary tube so that the

closed end is near the centre of the bulb of the thermometer, the immersion mark of

which is at the level of the surface of the liquid. Record the temperature at which the

last particle passes into the liquid phase.

II. Melting point – open capillary method.

For certain substances, the following method is used to determine the melting

point (also referred to as slip point and rising melting point when determined by this

method).

Use glass capillary tubes open at both ends, about 80 mm long, having an

external diameter of 1.4 mm to 1.5 mm and an internal diameter of 1.0 mm to

1.2 mm.

Introduce into each of 5 capillary tubes a sufficient amount of the substance,

previously treated as described, to form in each tube a column about 10 mm high and

allow the tubes to stand for the appropriate time and at the prescribed temperature.

Unless otherwise prescribed, substances with a waxy consistency are carefully

and completely melted on a water-bath before introduction into the capillary tubes.

Allow the tubes to stand at 2-8 °C for 2 h.

Attach one of the tubes to a thermometer graduated in 0.5 °C so that the

substance is close to the bulb of the thermometer. Introduce the thermometer with the

attached tube into a beaker so that the distance between the bottom of the beaker and

the lower part of the bulb of the thermometer is 1 cm. Fill the beaker with water to a

depth of 5 cm. Increase the temperature of the water gradually at a rate of 1 °C/min.

82

The temperature at which the substance begins to rise in the capillary tube is

regarded as the melting point.

Repeat the operation with the other 4 capillary tubes and calculate the result as

the mean of the 5 readings.

III. Melting point – instantaneous method.

The instantaneous melting point is calculated using the expression:

,2

)( 21 tt

in which t1 is the first temperature and t2 the second temperature read under the

conditions stated below.

Apparatus. The apparatus consists of a metal block resistant to the substance to

be examined, of good heat-conducting capacity, such as brass, with a carefully

polished plane upper surface. The block is uniformly heated throughout its mass by

means of a micro-adjustable gas heater or an electric heating device with fine

adjustment. The block has a cylindrical cavity, wide enough to accomodate a

thermometer, which should be maintained with the mercury column in the same

position during the calibration of the apparatus and the determination of the melting

point of the substance to be examined. The cylindrical cavity is parallel to the upper

polished surface of the block and about 3 mm from it. The apparatus is calibrated

using appropriate substances of known melting point.

Method. Heat the block at a suitably rapid rate to a temperature about 10 °C

below the presumed melting temperature, then adjust the heating rate to about 1 °C

per minute. At regular intervals drop a few particles of powdered and, where

appropriate, dried substance, prepared as for the capillary tube method, onto the block

in the vicinity of the thermometer bulb, cleaning the surface after each test. Record

the temperature t1 at which the substance melts instantaneously for the first time in

contact with the metal. Stop the heating. During cooling drop a few particles of the

substance at regular intervals on the block, cleaning the surface after each test.

Record the temperature t2 at which the substance ceases to melt instantaneously when

it comes in contact with the metal

Determination of boiling point

The boiling point is the corrected temperature at which the vapour pressure of a

liquid is equal to 101.3 kPa.

Apparatus. The apparatus is that used for Distillation Range with the exception

that the thermometer is inserted in the neck of the flask so that the lower end of the

mercury reservoir is level with the lower end of the neck of the distillation flask and

that the flask is placed on a plate of isolating material pierced by a hole 35 mm in

diameter.

83

Method. Place in the flask (A) 20 ml of the liquid to be examined and a few

pieces of porous material. Heat the flask so that boiling is rapidly achieved and record

the temperature at which liquid runs from the side-arm into the condenser.

Correct the observed temperature for barometric pressure by means of the

formula:

t1 = t2 + (101.3 - b)

t1 – the correct temperature,

t2 – the observed temperature at barometric pressure b,

k – the correction factor as shown in Tables,

b – the barometric pressure, in kPa, at the time of determination.

Determination of density

The relative density of a substance is the ratio of the mass of a certain volume

of the substance to the mass of an equal volume of water, both weighed at 20 °C.

Value of density confirms identification, and on occasion (an ethyl alcohol,

glycerol etc) - and quantitative maintenance of medicinal substances.

According to EP and SPU density is determined by tree methods:

1. By pyknometer (gravimetric) accuracy - 0,001.

0012,0)(

99703,0)(

01

02

mm

mm

where that is

mo - mass of empty pyknometer;

m1 - is mass of pyknometer with water;

m2-; it is mass of pyknometer with the explored liquid;

0,0012 is air density at 20°С and 1011 kPa;

84

0,99703 is water density at 20°С (with air density).

2. By areometer (accuracy 0,01) for determination of liquids density.

3. Method for determination of waxes and fats.

0012,0)()(

99703,0)(

321

02

mmmm

mm

m - is mass of empty pyknometer;

m1 - is mass of pyknometer with water;

m2 - is mass of pyknometer with fat;

m3 - is mass of pyknometer with water and fat.

Determination of refractive index (refractometry)

The refractive index of a medium with reference to air is equal to the ratio of

the sine of the angle of incidence of a beam of light in air to the sine of the angle of

refraction of the refracted beam in the given medium.

The index of refraction depends on a temperature, wavelength light, and in

solutions - from nature of solvent and concentration. Dependence of refractive index

is expressed by formulas:

n=no + C . F

,)( 0

F

nnC

where

C- is concentration of solution (%);

no -is index of refraction of solvent;

n - is index of refraction of solution;

F - is correction factor (value of increasing of refractive index at increasing of

concentration on 1%). Determination is carried out at the temperature of 20°С and

wave-length D of sodium spectrum (589.3 nm).

Index of water refraction:

nD20

= 1,3330

If the solution consisting of a few ingredients

n= n0 +n1 +n2 +……..+ ni

or

n= n0 + C1.F1 + C2

.F2 +……..+Ci.Fi

Concentration of one of components in mixture can be expressed by formula:

1

220

1

]........)[(

F

FCFCnnC ii

Determination of specific rotation (polarimetry) Optical rotation is the property displayed by chiral substances of rotation the

plane of polarised light.

Optical rotation is considered to be positive (+) for dextrorotatory substances

(i.e. those rotate the plane of polarisation in a clockwise direction) and negative (-)

for laevorotatory substances.

85

The specific optical rotation [αm]t

λ is the rotation expressed in radians (rad) ,

measured at the temperature t and at the wavelength λ given by a 1 m thickness of

liquid or a solution containing 1 kg/m 3 of optically active substance.

For the liquid individual substances the specific rotation is found out by

formula:

lD

20][ , where

α- is angle of rotation in degrees read at 20°C;

ρ -is density at 20°C in grams per cubic centimeter;

l - is length in decimeters of the polarimeter tube.

For solutions:

lCD

100][ 20

, l

CD

20][

100

C- is concentration of solution (%).

For qualitative and quantitative analysis of organic substances the spectral

methods – such as UV-, IR- and NMR, photoelectrocolorimetry, fluorimetry are often

used.

For chemical analysis of this group of substances the element analysis and

analysis by functional groups is used.

Element analysis of organic substances

The element analysis allows defining the structural elements of substances.

Determination is based on preliminary mineralization - destruction of substance with

formation of simple inorganic substances.

Determination of carbon and hydrogen

Burning with copper oxide:

the substance is mixed with copper oxide, put into the tube with barium

hydroxide water and heated on flame; a carbon forms carbon dioxide, which causes

dimness of barium hydroxide water:

CO2 + Ba(OH)2 BaCO3 + H2O

The presence of hydrogen conduces to formation of water found out as drops in

overhead part of the test tube. Colourless crystals of copper sulphate get dark blue.

CuSO4 . H2O + 4H2O CuSO4 . 5H2O

On thermic decomposition of substance with sulphur, sodium sulphite or

thiosulphate hydrogen associates into hydrosulphur, which is determined with leaden

paper:

H2S + (CH3COO)2Pb PbS + 2CH3COOH

Determination of oxygen

Oxygen is usually determined by functional groups. The determination of

oxygen is often related with difficulties and often confirmed only after the

determination of functional groups (carboxy-, hydroxy-, nitro- and etc).

Determination of nitrogen

Nitrogen can be determined by the smell of the burnt horn at incineration.

86

1. Method of Kal - burning with the mixture of thiosulphate and carbonate of

sodium. In result of this reaction forms sodium thiocyanate, which gives reaction

with salts of iron (III). The red painting appears:

3SCN- + Fe3+

Fe(SCN)3

2. Incineration with metallic sodium and reaction of Berlin azure formation:

2NaCN + FeSO4 Fe(CN)2 + Na2SO4

Fe(CN)2 + 4NaCN Na4[Fe(CN)6]

3Na4[Fe(CN)6] + 4FeCl3 Fe4[Fe(CN)6]3 + 12NaCl

This method is very sensitive.

Detection of sulphur

Sulphur can be detected by the Lassaigne test after heating with metallic

sodium. Organically integrated sulphur gets into sodium sulphide, which is detected

by appearance of the red-violet colouring of sodium nitroprusside:

Na2S + Na2[Fe(CN)5NO] Na4[Fe(CN)5NOS]

Detection of halogens

Chlorine, bromine or iodine can often be detected by heating the substance on a

piece of clean, oxidised copper wire, owing to the formation volatile chloride,

bromide, or iodide of copper, the flame becomes green (Beilstein's test ).

CuO + HalR CuHal2 + CO2 + H2O

On heating halogens of copper (II) are reduced:

CuHal2 Cu2Hal2

Fluorine derivatives can’t be determined by the colouring of flame, because

Cu2F2;- is non-volatile substance.

It is possible to detect chloride, bromide, or iodide by ordinary analytical

reactions after mineralization.

If halogen exists as a salt of halogenderivative acid (in ionised condition), these

reactions can be conducted without mineralization.

Analysis by functional groups

Functional groups are atoms or groups of atoms, which stipulate properties of

substances and determine character of reactions of their identification.

The most general are resulted below:

Alcohol hydroxyl

1. Reaction of esterification in the presence of anhydrous sulphuric acid: O

OH

O

ORR-OH + R`C

-H2OR`C

The products of reaction usually have the characteristic fruit smell.

2. Oxidation.

O

H

O

OHR-CH2OH RC

[O]RC

[O]

87

The products of reactions are determined by the smell, physical constants or by

products of further transformations.

Phenol hydroxyl

1 Formation of complex salts with the salts of heavy metals. The structure and

colouring of these complexes are various and depend on the presence and position of

phenol hydroxyl and other functional groups in the molecule. This reaction is

sensitive enough and allows detecting phenols as impurities.

2. Etherification. Products are determined by physical constants.

3. Reactions of substitution on benzene ring:

а) bromination: OH OH

Br Br

Br

+3Br2 +3HBr

b) nitration:

OH N OH

O

O

N O

O

OH

+ NHO3

+

-

+

--H2O

4. Oxidation (indophenol test):

OH O O O NH

OH

OHO N

[O] NH3

quinone quinone imine

indophenol 5. Diazotization:

OH

N

N N

OH N+

Cl

+

- NaOH

Aldehyde group

Aldehydes have very high reactive ability. The reactions of addition,

substitution, oxidation, reduction and polymerisation are characteristic for these

substances.

1. Reactions of condensation:

88

O

HN-R`RC +R`NH2 -H2O

R-CH

It is used for determining of primary aromatic nitrogen (lignin test).

O

HN-NH-R`RC +R`NHNH2 -H2O

R-CH

2. Reactions of oxidation are reduction:

a) reaction with ammonium silver nitrate solution (Tollense): O

HRC + H2O2[Ag(NH3)2]NO3 2 Ag + 2NH4NO3 + RCOONH4 + NH3+

The raid of metallic silver appears on the walls of test tube. This reaction is

given by all the aldehydes.

b) cupri-tartaric solution (Fehling reagent):

Cu2+

+ 2OH- Cu(OH)2 COONa

CHOH

CHOH

COOK

COO

CHOH

CHOH

COOK

OOC

HOHC

HOHC

NaOOC

Cu

2 +Cu(OH)2+NaOH+KOH

2KNa[Cu(C4H4O6)2]+RCOH+3NaOH+2KOH 2CuOH +2RCOONa+4KNaC4H4O6+2H2O

2CuOH

t o

Cu2O +H2O

On heating red precipitate forms only in the presence of aliphatic aldehydes.

This reaction often used in the analysis of sugars.

d) with alkaline potassium tetraiodomercurate solution (Nessler reagent): O

H

O

OKRCRC K2[HgI4] + 3KOH +Hg +4KI + 2H2O +

Reaction is very sensitive and often used for determining of aldehydes as

impurities.

Carboxyl group

1. Reactions with the salts of heavy metals.

2. Esterification.

3. At adding of sodium hydrogen carbonate solution (unlike alcohols and

phenols) carbon dioxide is educed.

Ester group

1. Hydrolysis. O

OR`R-COOH + R`OH+H2ORC

The products of reaction are determined by physical constants.

2. Reaction with hydroxylamine. Complexes with iron have red-violet colour.

89

O

OR`

O

NHOH+ R`OHRC

NH2OH

RC

O

NHOH

O

NHO

O

NHO

RC

FeCl3

RC RC

3

Fe

2

Fe Cl;

Amide group

1. Alkaline hydrolysis.

O

NHR`

O

ONa+ R`NH2RC

NaOH

RC

The educed amines are determined by the smell.

2. Reaction with hydroxylamine.

Primary aromatic aminogroup

1. Reaction of diazotization. The products obtained are of orange red

colour (or precipitate).

NH2

RN

RN

ONa

N

R

N

NaO

NaNO2

HCl

+

Cl-

2. Formation of Schiff’s bases (lignin test). The products obtained are of

yellow colour.

NH2

R R'C

H

O RN CH

R'+

- H2O

3. Isonitril test. The product obtained is characterized by the specific

unpleasant smell: N CNH

2

RR

+ 3 NaOH + CHCl3 + 3NaCl +3H2O

During use reactions for functional analysis it is necessary to take into account

chemical abilities of all the parts of molecule.

90

Chapter 8. MEDICINAL SUBSTANCES, WHICH ARE THE

DERIVATIVES OF SATURATED HALOCARBONS

AND ALCOHOLS OF ALIPHATIC ORIGIN

Plan

1. Medicinal substances with organic halogen (chloroform, iodoform,

ethyl chloride, halothane (phthorotanum)).

2. Medicinal substances – aliphatic alcohols (ethanol, glycerol).

Halocarbons are formed when one or some atoms of hydrogen in hydrocarbon

molecule substituted by halogens.

The general stage in analysis of these compounds is determination of halogen.

For this purpose is usually used the Beilstein’s test. For confirming of halogen by

analytical reactions it is necessary to transfer it into ionised condition. During

mineralization the simple inorganic substances are formed.

This class of compounds includes such substances as: chloroform, iodoform,

ethylene chloride and halothane.

Chloroform (Chloroformium)

CHCl3

Trichloromethane

Preparation

Electrolysis of sodium chloride in the presence of alcohol or acetone:

2NaOH + Cl2 NaClO + NaCl + H2O

C

H

O

CH3

C2H5OH + NaClO + NaCl + H2O

C

H

O

CH3

C

H

O

Cl3C+ 3NaOCl + 3NaOH

C

H

O

Cl3C + NaOH CHCl3 + HCOONa

Properties Colourless, transparent, heavy and mobile volatile liquid with the

characteristic odour and sweet taste. It is mixed in all proportions with an anhydrous

ethanol, ether and petrol, essential and fatty oils. Non-mixed with glycerol.

During storage can be oxidized.

C

Cl

Cl

O2CHCl3 + O2 2HOCCl32 + 2HCl

91

C

Cl

Cl

O2 + O2 2CO2 + 2Cl2

To avoid oxidation for chloroform is added ethanol (0,6 – 1%), which used as

preservative substance:

C

Cl

Cl

O C

OC2H

5

OC2H

5

O

C

H

O

CH3

+ 2C2H5OH + 2HCl

HCl + C2H5OH C2H5Cl + H2O

Cl2 + C2H5OH + 2HCl

CCl Cl

O

2CHCl3 + O2 2CCl3(OH) 2 + 2HCl

CCl Cl

O

2 + O2 2CO2 + 2Cl2

Identification

Physical constants: boiling point and density.

According to Pharmacopoeia it is necessary to make quantification of

ethanol:

3C2H5OH + 2K2Cr2O7 +16HNO3 4Cr(NO3)3 + 3CH3COOH + 4KNO3 + 11H2O

excess

K2Cr2O7 + 6KI + 14HNO3 8KNO3 + 2Cr(NO3)3 + 3I2 + 7H2O

I2 + 2Na2S2O3 2NaI + Na2S4O6

S=3/2.The indicator is starch.

Purity Free chlorine: Cl2 + 2KI I2 + 2KCl

Aldehydes: O

H

O

OKRCRC K2[HgI4] + 3KOH +Hg +4KI + 2H2O +

Usage External medicine for massages at neuralgia.

At poisonings with arsine, for laboratory works as preservative.

Storage In well-stoppered orange glass bottles, in cool place.

92

Iodoform (Iodoformium)

CHI3

Triiodomethane

Preparation

C2H5OH + 4I2 + 3Na2CO3 CHI3 + 5NaI + HCOONa + 2H2O +

3CO2

Properties Yellow powder with the specific odour. It melts at first, and then

decomposes with educing of violet steams of iodine. Volatile already at room

temperature, distillated with water vapour. Solutions of substance quickly decompose

under action of light and air with educing of iodine.

Identification On heating a violet steams of iodine are educed:

2CHI3 + 2O2 3I2 + CO + CO2 + H2O

Assay Argentometry (Volhard method). The substance is dissolved in

water-alcohol mixture, heated with silver nitrate solution in the presence of nitric

acid. The excess of silver nitrate is titrated with ammonia thiocyanate using

ferric-ammonia sulphate solution as an indicator. S=1/3.

to

CHI3 + 3AgNO3 + H2O 3AgI + 3HNO3 + CO

AgNO3 + NH4SCN AgSCN + NH4NO3

Fe3+

+ 3SCN- Fe(SCN)3

Carry out a blank titration.

Usage Antiseptic. Use externally as powder, ointments, pastes for

treatment of wounds and ulcers.

Storage In well-closed containers, protected from light.

Ethyl chloride (Aethylii chloridum)

C2H5Cl

Preparation

1. Chlorination of ethane: C2H6 + Cl2 C2H5Cl + HCl

2. Hydrochloration of ethylene: CH2CH2 + HCl CH3CH2Cl

Properties Colourless, very volatile liquid. Catches fire easily. It burns with a

green flame. The boiling temperature is 12º C .

Identification

On heating with alkali:

C2H5Cl + KOH C2H5OH + KCl

93

carry out reactions on alcohol:

C2H5OH + 4I2 + 6KOH CHI3 + 5KI + HCOOK + 5H2O yellow

and reactions of chlorides.

Quality is confirmed by physical constants – boiling point and density.

Purity Impurity of ethanol is determined by iodoform test (see above).

Usage For short-term narcosis or local anaesthesia, due to cooling of tissues.

Storage In ampules, or in bottles with special stoppers, in cool and protected

from light action place.

Halothane (Phthorotanum)

CF3-CHClBr

(RS)-2-bromo-2-chloro-1,1,1-trifluoroethane

Preparation F

3C CH

2Cl F

3C CHClBr+ Br2 + HBr

Properties A clear, colourless, mobile, heavy, non-flammable liquid, slightly

soluble in water, miscible with ethanol, with ether and with trichloroethylene.

It contains 0,01% of thymol as a stabiliser.

Identification

1. IR-spectrum.

2. To the substance add 2-methyl-2-propanol in a test-tube. Add copper edetate

solution, concentrated ammonia and a mixture of strong hydrogen peroxide solution

and water (solution a). Prepare a blank at the same time (solution b). Place both tubes

in a water-bath, cool, and then add glacial acetic acid. To the each of solutions add a

mixture of freshly prepared alizarin solution and zirconyl nitrate solution. Solution

(a) is yellow and solution (b) is red.

The obtained fluorides decompose the complex of alizarin with zirconium (in

the examined test the red colouring becomes yellow; in the blank test the red

colouring remains):

O

O

O

OH

SO3Na

O

O

OH

OH

SO3Na

Zr/4

+ 6F-

+ [ZrF6]2 -

To 1 ml of each of solutions add buffer solution pH 5.2, phenol red solution

and chloramine solution. Solution (a) is bluish-violet and solution (b) is yellow.

94

At pH 5.2 the phenol red has a yellow colouring. In the presence of bromides

and under action of chloramine it becomes bromothymol blue, which has a bluish-

violet colouring:

SO3H

O

C

HO

Br

SO3H

O

Br

BrC

HO

Br

+ 4Br2 +4HBr

To 2 ml of each of solutions add sulphuric acid, acetone and potassium

bromate solution. Warm the tubes in a water-bath, cool and add nitric acid and silver

nitrate solution. Solution (a) is opalescent and a white precipitate is formed after a

few minutes; solution (b) remains clear.

Bromides are oxidised to free bromine by interaction with potassium bromate:

5Br-+BrO3

-+6H

+3Br2+3H2O;

and then they are deleted as pentabromoacetone:

CH3COCH3+5Br2CBr3COCHBr2+HBr;

chlorides in the solution are detected with silver nitrate solution:

Cl-+Ag

+AgCl

Purity Contents of thymol is determined by gas-chromatography.

Usage General anaesthetic.

Storage Store in an airtight container, protected from light, at temperature

25C. The choice of material for the container is made taking into account the

particular reactivity of halothane with certain metals. In the end of each 6 months of

storage the substance is re-examined.

Alcohols – are organic compounds with the general formula R-OH. They are

classified as primary, secondary or tertiary according to the kind of carbon containing

the –OH group.

Alcohols are enough inert chemically; they have weak-acid properties, inclined

to oxidation and enter into reactions of substitution (for example, esterification).

The main pharmacological action of low-molecular alcohols is influence on

central nervous system. High-molecular alcohols (more than 16 atoms of carbon)

practically do not influence on organism.

The simplest representatives are ethanol and glycerol.

95

Ethanol (Spiritus aethylicus)

CH3-CH2OH

Preparation

Alcohol fermentation of starch:

During manufacturing of alcohol can be obtained such side products as pyruvic

acid, acetaldehyde, glycerol, and fusel oil. For purifying ethyl alcohol must be

distilled.

Properties Colourless, clear, volatile, flammable liquid, hygroscopic. Miscible

with water and with methylene chloride. It burns with a blue, smokeless flame.

Boiling point 78ºC.

Identification

1. Relative density (0.805- 0.812).

2. IR-spectrum.

3. Mix the substance with solution of potassium permanganate and dilute

sulphuric acid. Cover immediately with a filter paper moistened with a freshly

prepared solution containing of sodium nitroprusside and piperazine hydrate in water.

After a few minutes an intense blue colour appears on the paper and becomes paler

after 10-15 minutes.

4. To the substance add water and dilute sodium hydroxide solution, then

slowly add 0.05 M iodine. A yellow precipitate is formed within 30 min (iodoform

test):

C2H5OH + 4I2 + 6KOH CHI3 + 5KI + HCOOK + 5H2O

Purity Volatile impurities determine by gas-chromatography method.

Assay By Pharmacopoeia no assay is proposed.

Non-Pharmacopoeial method – dichromatometry:

3C2H5OH + 2K2Cr2O7 +16HNO3 4Cr(NO3)3 + 3CH3COOH + 4KNO3 + 11H2O excess

K2Cr2O7 + 6KI + 14HNO3 8KNO3 + 2Cr(NO3)3 + 3I2 + 7H2O

I2 + 2Na2S2O3 2NaI + Na2S4O6

nC6H

12O

6(C

6H

10O

5)n nC

12H

22O

11+ OnH

22H

nC2H

5OH

O

nCO2+

starch

amylase, 60 C

maltose

, maltase

glucose

zymase , 30-33 C

fermentation

2

2

2

o

o

2

5C2H5OH +2KMnO4+3H2SO4

CH3 C

O

H + K2SO4 + 2MnSO4 8H2O+

96

S=3/2.The indicator is starch.

Usage External antiseptic and irritant substance for massages and compresses.

It is manufactured as 95%, 90%, 70%, 40% aqueous solutions.

Storage In well-closed containers, protected from light.

Glycerol (Glycerinum)

CH

2

CH

C

OH

OH

OHH2

Propane-1,2,3-triol

Preparation By saponification of fats:

CH2

CH

C

O

O

O

C

C

C

O

O

O

R

R

R

CH2

CH

C

OH

OH

OHH2

OH-

H2

+ 3RCOO-

Properties Syrupy liquid, unctuous to the touch, colourless or almost

colourless, clear, very hygroscopic. Miscible with water and with alcohol, slightly

soluble in acetone, practically insoluble in fatty oils and in essential oils.

Identification

1. Refractive index (1.470-1.475).

2. IR-spectrum.

3. Reaction with nitric acid and potassium dichromate solution.

A blue colouring ring develops at the interface of the liquids within 10 min, the

blue colour does not diffuse into the lower layer.

4. Heat the substance with potassium hydrogen sulphate in an evaporating dish.

Vapours are evolved which blacken filter paper impregnated with alkaline potassium

tetraiodomercurate solution:

CH2OH

CH2OH

KICHOHKOH

C HO

CHK

2HgI

4

CH2

O

CH2

CH ++ 2+ OHg H

C OK,2KHSO4 3

2

Assay Indirect alkalimetry method.

Mix the substance with water. Add sulphuric acid and sodium periodate. Allow

to stand protected from light for 15 min. Add the solution of ethylene glycol and

allow to stand protected from light for 20 min. Using phenolphthalein as indicator,

titrate with 0.1 M sodium hydroxide. S=1. Carry out a blank titration.

97

+ ++ + O2

CH2

CH2

CH NaIO4

OH

OH

OH

HC

H

O

NaIO3

HCOOH H2 2 2

The educed formic acid is titrated with sodium hydroxide solution:

HCOOH NaOH HCOONa OH2++

2. Acetilation:

CH2

CH

C

OH

OH

OH

CH2

CH

C

O

O

O

COCH3

COCH3

COCH3

H2

+ 3(CH3CO)2O

H2

+ 3CH3COOH

After destruction of acetic anhydride the solution analyzed is neutralized with

an alkali (the indicator is phenolphthalein) and boiled with the sodium hydroxide

solution: CH

2

CH

C

O

O

O

COCH3

COCH3

COCH3

CH2

CH

C

OH

OH

OHH2

+ 3NaOH

H2

+ 3CH3COONa

The excess of the alkali is titrated with hydrochloric acid; S=1/3.

NaOH + HCl NaCl + H2O

3. Back dichromatometry; s=3/7. CH

2

CH

C

OH

OH

OHH2

3 + 7K2Cr2O7 + 28H2SO4 9CO2+ 7K2SO4 + 7Cr2(SO4)3 + 40H2O

The excess of potassium dichromate is titrated with FeSO4·(NH4)2SO4·6H2O: K2Cr2O7 + 6Fe(NH4)2(SO4)2 + 7H2SO4 Cr2(SO4)3 + 3Fe2(SO4)3 + K2SO4 + 6(NH4)2SO4 + 7H2O

Usage It is a base for ointments and solutions. Anhydrous glycerol can cause

burns.

Storage In an airtight container.

98

Chapter 9. MEDICINAL SUBSTANCES DERIVATIVES OF

ALDEHYDES AND CARBOXYLIC ACIDS OF ALIPHATIC ORIGIN

Plan

1. Medicinal substances derivatives of aldehydes (solution of formaldehyde,

methenamine, chloral hydrate).

2. Salts of aliphatic carboxylic acids (potassium acetate, calcium lactate,

calcium gluconate, sodium citrate for injections, sodium hydrogen citrate).

Aldehydes – are compounds, which contain the aldehyde (carbonyl) group.

Aldehydes have strong reactive ability. They can get into reactions of oxidation

(sometimes reduction), addition, and polymerisation.

This chemical class of substances includes formaldehyde, hexamine and

chloral hydrate.

Medicinal substances derivatives of aldehydes

Formaldehyde solution 35% ( 35% Solutio Formaldehydi)

C

H

O

H

Preparation

Oxidation of methyl alcohol:

C

H

O

H2CH3OH + O2

500 - 600O

C

Kt2 + 2H2O

Oxidation of methane (Medvedev method):

C

H

O

H2CH4 + O22CH3OH

O2

+ 2H2O2

Properties A clear, colourless liquid, miscible with water and with alcohol. It

may be cloudy after storage.

Methyl alcohol is added as a stabiliser (to 15%) to avoid paraformaldehyde

formation.

Identification

1. Reaction with chromotropic acid in the presence of sulphuric acid. A violet-

blue or violet-red colour develops within 5 min:

99

OH

SO3H

SO3H

OH

O

H

OH

SO3H

SO3H

OH

CH2

HO3S

OH

HO3S

OH

HC+-H2O

[O]2

HO

3S

O

HO3S

OH

OH

SO3H

SO3H

OH

CH

2. Reaction with phenyl hydrazine hydrochloride and potassium ferricyanide

solution in the presence of hydrochloric acid. An intense red colour is formed.

To the substance add silver-nitrate solution and dilute ammonia until slightly

alkaline. Heat on a water-bath – a grey precipitate or a silver mirror is formed:

O

HRC + H2O2[Ag(NH3)2]NO3 2 Ag + 2NH4NO3 + HCOONH4 + NH3+H

Methanol (from 9 to 15%) is determined by gas-chromatography method

(internal standard – ethanol R1).

The non-Pharmacopoean reaction – with the salicylic acid in the presence of

the concentrated sulphuric acid (red colour):

OH

COOH CH2

OH

COOHHOOC

HO

CHHOOC

HO

COOH

O

2 +HCOHconc.H2SO4

-H2O

[O]

Some authors propose such structure:

HOOC

HO

COOH

O

C

OH

COOH

Purity Acidity is caused by formed formic acid:

C

H

O

H C

OH

O

H+ H2O + CH3OH2

It is detected with phenolphthalein solution.

100

Methanol is determined by gas chromatography.

Assay

1. Iodometry. S=1.

To the solution of substance add sodium hydroxide solution, iodine and dilute

sulphuric acid. Titrate with sodium thiosulphate using starch solution as indicator.

C

H

O

HC

H

O

H + I2 + H2O + 2HI

Sodium hydroxide solution is added because HI in acid medium can reduce

formic acid to formaldehyde.

I2 + 2NaOH NaI + NaOI + H2O

C

H

O

H C

OH

O

HNaOI + NaI +

NaI + NaOI + H2SO4 I2 + Na2SO4 + H2O

I2 +2Na2S2O3 2NaI + Na2S4O6

2. Oxidation with hydrogen peroxide in the alkaline medium (S =1):

C

H

O

H C

ONa

O

H+ H2O2 + NaOH + H2O

NaOH + HCl NaCl + H2O

3. Titration with the sodium sulphite (for quantification of formaldehyde in the

«Formidron»); (S =1):

C

H

O

H C

SO3Na

OH

H H+ NaSO3 + H2O + NaOH

NaOH + HCl NaCl + H2O

4. Refractometry.

Usage Used in the treatment of warts and as antiseptic, disinfectant and

deodorant; in preservation of anatomical specimens. Formalin is a protoplasmatic

poison!

Storage In well-closed containers, protected from light, at a temperature of

15ºC to 25ºC.

Methenamine (Hexamethylentetraminum)

N

N

NN

1,3,5,7-tetra-azotricyclo[3.3.1.13,7]decane

101

Preparation Mix the solutions of formaldehyde and ammonia.

N

N

NN

CH

H

O

CH

H

OH

NH2

CH2

NHNH

NH

NH

CH

H

O

+ NH3- H2O NH3

3

Summary:

N

N

NN

CH

H

O

6 + 4NH3 + 6H2O

Properties A white, crystalline powder or colourless crystals, freely soluble in

water, soluble in alcohol and in methylene chloride.

Identification

1. IR-spectrum.

2. To the solution of substance add sulphuric acid and immediately heat to

boiling. Allow to cool, then to the solution add water and acetylacetone reagent. Heat

for 5 min. An intense yellow colour develops.

3. To the solution of substance add dilute sulphuric acid and immediately

heat to boiling. The solution gives reaction of ammonium salt and salts of volatile

bases.

Dissolve the substance in water and acidify with dilute hydrochloric acid. Add

potassium iodobismuthate solution. An orange precipitate is formed immediately.

4. With silver nitrate solution – white precipitate appears:

N

N

NN N

N

NN

2 + 3AgNO32 3AgNO3

.

Assay

1. Dissolve the substance in methanol. Titrate with 0.1 M perchloric acid,

determining the end-point potentiometrically. S=1.

2. Acid-base titration. The indicator is methyl red solution. S =1/2:

(CH2 )6N4+ 2H2SO4

+ 6H2O 6HC H

O

+ 2(NH4)2SO4

(NH4)2SO4 + 2NaOHto

Na2SO4+ 2NH4OH

+NH4OH NH3 H2O

(CH2 )6N4+HClO4 (CH2)6N4

. HClO4

102

N

N

NN

CH

H

O

+ 2H2SO4 + 6H2O 6 + 2(NH4)2SO4

tO

H2SO4 + 2NaOH Na2SO4 + 2H2O

3. Acidimetry (with the mixed indicator – methyl orange and methyl blue).

S=1:

N

N

NN N

N

NN

+ HCl . HCl

4. Iodine monochloride method (iodchlorimetry). Back titration, the indicator is

starch solution. S=1/2:

N

N

NN N

N

NN

+ 2ICl . 2ICl

ICl + KI I2 + KCl

I2 + 2Na2S2O3 2NaI + Na2S4O6

5. Argentometry by Volhard method. Back titration; the excess of silver nitrate

is titrated with ammonia thiocyanate using ferric-ammonia sulphate as an indicator.

S=2/3:

N

N

NN N

N

NN

2 + 3AgNO32 3AgNO3

.

AgNO3 + NH4SCN AgSCN + NH4NO3

3NH4SCN + Fe(NH4)(SO4)2 Fe(SCN)3 + 2(NH4)2SO4

Usage Hexamine is used as a urinary antiseptic. It is used at poisonings by salts

of heavy metals as antidote.

Storage In well-stoppered bottles, protected from light.

Chloral hydrate (Chloralum hydratum)

Cl3C C

OH

OH

H

2,2,2-trichloroethane-1,1-diol

103

Preparation

C

H

O

CH3

C

OC2H

5

OH

CH3

H C

OC2H

5

OH

Cl3C H

C

H

O

Cl3C C

OH

OH

CH3

H

C2H5OHCl2, FeCl3 C2H5OH Cl2

- HCl

H2SO4

H2O

trichloracetic aldehyde

Properties Transparent, colourless crystals, very soluble in water, freely

soluble in alcohol and in ether.

Under light action slowly decomposes (oxidation):

C

OH

OH

Cl3C H C

H

O

C

Cl

Cl

H Cl3C COOH+ + HCl + H2O 2

Identification

1. Add dilute sodium hydroxide solution – the mixture becomes cloudy

and, when heated, gives off an odour of chloroform:

Cl3C C

OH

OH

H + NaOH CHCl3 + HCOONa + H2O

2. To the solution of substance add sodium sulphide solution – a yellow

colour develops which quickly becomes reddish-brown. On standing for a short time,

a red precipitate may be formed.

The non – Pharmacopoeial reaction – with silver ammonia-nitrate solution:

O

HCCl3C + H2O2[Ag(NH3)2]NO3 2 Ag + 2NH4NO3 + CCl3COONH4 + NH3+

Purity Chloral alcoholate is the intermediate product of synthesis; it is detected

with sodium hydroxide solution on adding of iodine (iodoform test).

CCl3CH(OH)OC2H5 + NaOH CHCl3 + HCOONa + C2H5OH

C2H5OH + 4I2 + 6NaOH CHI3 + 5NaI + HCOONa + 5H2O

Assay

1. Dissolve the substance in water and add sodium hydroxide solution, titrate

with sulphuric acid using phenolphthalein as indicator.

Titrate the neutralised solution with silver nitrate, using potassium chromate

solution as indicator. S =1.

CCl3CH(OH)2 + NaOH CHCl3 + HCOONa + H2O excess

2NaOH + Н2SO4 Na2SO4 +2H2O

CHCl3 + 4NaOH 3NaCl +HCOONa + 2H2O

104

The educed sodium chloride is titrated with silver nitrate solution:

NaCl +AgNO3 AgCl +NaNO3

AgNO3 + K2CrO4 Ag2CrO4 + 2KNO3

Volume of titrant = ])[(342 AgNOSOHNaOH VVV

2. Iodometry (indicator is starch). S=1.

2CCl3CH(OH)2 + 2I2 + 3Na2CO3 2CCl3COONa + 4NaI + 3H2O + 3CO2

3. Acid-base titration, the indicator is phenolphthalein solution. Carry out a

dlank titration. S=1.

CCl3CH(OH)2 + NaOH CHCl3 + HCOONa + H2O excess

NaOH + HCl NaCl + H2O

Usage Hypnotic.

Storage In an airtight container.

Derivatives of carboxylic acids Carboxylic acids have in their molecules carboxyl group -COOH.

General properties of this substances are: ability to react with alkali, to form

precipitates with the salts of heavy metals, to get into reactions of esterification with

alcohols etc.

In free condition these substances are not used in medicine because of their

irritant action. In the most causes use their salts: potassium acetate, calcium lactate,

calcium gluconate, sodium citrate etc.

Potassium acetate (Kalii acetas)

CH3COOK

Preparation Neutralisation of acetic acid with potassium carbonate:

2CH3COOH + K2CO3 2CH3COOK + H2O + CO2

Properties A white, crystalline powder or colourless crystals, deliquescent,

very soluble in water, freely soluble in alcohol.

Identification

1. Reactions of acetate-ion:

a) reaction of ester forming with ethanol ( the specific fruit odour):

CH3COOK + C2H5OH + conc. H2SO4 CH3COOC2H5 + K2SO4 + H2O

b) interaction with the salts of ferric. Brown-red colouring:

9CH3COOK + 3FeCl3 + 2H2O 2CH3COOH [Fe3(OH)2(CH3COO)6]+CH3COO-+9KCl

c) it gives the reaction of acetyl:

105

La3+

+ 3CH3COO- + 2H2O La(OH)2CH3COO + 2CH3COOH

Blue

2. Reactions of К+:

a) reaction with tartaric acid:

K+ + HC4H4O6

- KHC4H4O6

b) reaction with sodium cobaltinitrite:

2K+ + Na

+ + [Co(NO2)6]

3- K2Na[Co(NO2)6]

c) colouring of flame (a violet colour).

Assay

1. Non-aqueous titration.

Dissolve the substance in anhydrous acetic acid. Add naphtholbenzein solution.

Titrate with 0.1 M perchloric acid. Carry out a blank titration. S=1.

CH3COOK + CH3COOH (CH3COOKH)+ . CH3COO-

HClO4 + CH3COOH (CH3COOH2)+ . ClO4

-

(CH3COOKH)+ . CH3COO- + (CH3COOH2)

+ . ClO4

- KClO4 +

3CH3COOH

Summary: CH3COOK + HClO4 CH3COOH + KClO4

2. Acidimetry (in liquid medicines). The indicator is tropaeolin-O. S=1.

CH3COOK + HCl CH3COOH + KCl

Usage Used in solutions for dialysis.

Storage In well-closed containers, protected from moisture.

Calcium lactate (Calcii lactas)

CH3

CH C

O

O

OH

-Ca

2

. 5H2O

Calcium bis(2-hydroxypropanoate)

Preparation Fermentation of sugary materials by pure cultures of lactic acid

bacteria in the presence of calcium carbonate.

C6H

12O

6 CH3CHCOOH

OH

CaCO3

CH3CH(OH)COO

Ca CO

2H

2O

2

+ +2

Properties A white or almost white, crystalline or granular powder, slightly

efflorescent, soluble in water, freely soluble in boiling water, very soluble in alcohol.

106

Identification

1. Reaction of lactate-ion.

Dissolve the substance in water R. Add bromine water R and dilute sulphuric

acid R. Heat on a water-bath until the colour is discharged, stirring occasionally with

a glass rod. Add ammonium sulphate R and mix. Add sodium nitroprusside R

solution in dilute sulphuric acid R. Still without mixing add the concentrated

ammonia R. Allow to stand for 30 min. A dark green ring appears at the junction of

the two liquids.

2. Reactions of Ca2+

.

The non-Pharmacopoeial reaction – with potassium permanganate solution

gets colourless; with forming of acetaldehyde (characteristic fruit odour).

CH3

CH C

O

O

OH

C

H

O

CH3

-Ca

2

+ 4KMnO4 + 11H2SO4

10 + 5CaSO4 + 10CO2 + 2K2SO4 + 4MnSO4 + 16H2O

Assay Complexometry (the indicator is calconcarboxylic acid ). Direct titration

at the presencse of concentrated sodium hydroxide solution. Calculate on an

anhydrous substance. S=1.

N N

OHHOOC OH

SO3HCa

N N

ONaOOC O

SO3Na

Ca

H 2O OH

2

NaOH H+

2++

+ 2

CH2

CH2

N

N

CH2COONa

CH2COO

CH2COO

CH2COONa

Ca

N N

ONaOOC O

SO3Na

Ca

H 2O OH

2

CH2

CH2

N

N

CH2COONa

CH2COOH

CH2COOH

CH2COONa

NaOH

N N

OHNaOOC OH

SO3Na

+

+

Usage It is the source of Са2+-

ions. Antiallergic medicine; used at poisonings

with salts of heavy metals like antidote.

Storage In a well-closed container.

107

Calcium gluconate (Calcii gluconas)

CH2OH

(CHOH)4

COO-2

Ca OH2

.

Calcium D-gluconate monohydrate

Preparation Electrochemical oxidation of glucose in the presence of calcium

carbonate and bromine:

CH2OH

(CHOH)4

COO-2

Ca

CH2OH

(CHOH)4

COH

Br2, H

2O

-HBr

CH2OH

(CHOH)4

COOH

CaCO3

-CO2

Properties A white, crystalline or granular powder, sparingly soluble in water,

freely soluble in boiling water.

Identification

1. Thin-layer chromatography.

2. Reactions of Ca2+

.

The non –Pharmacopoeial reaction: with FeCl3 solution. A light-green

colouring develops (reaction of gluconate-ion).

Purity Sucrose and reducing sugars are determined with cupri-tartaric solution

(Fehling reagent). No red precipitate is formed.

Assay Complexonometry (see calcium lactate).

Usage Used in treatment of calcium deficiency.

Storage In well-closed containers.

Sodium citrate for injections (Natrii citras pro injectionibus)

CH

2

C

CH2

OH

COONa

COONa

COONa

. 5 1/2H2O

Trisodium 2-hydroxypropane-1,2,3-tricarboxylate

Calculate with reference to the anhydrous substance.

108

Preparation

CH2

C

CH2

OH

COOH

COOH

COOH

CH2

C

CH2

OH

COONa

COONa

COONa

2 + 3Na2CO3 + 3H2O + 3CO22

Properties A white, crystalline powder or white, granular crystals, slightly

deliquescent in moist air, freely soluble in water, practically insoluble in alcohol.

Identification 1. Reaction of citrates.

Dissolve the substance in water R. Add sulphuric acid R and potassium

permanganate solution R. Warm until the colour of the permanganate is discharged.

Add sodium nitroprusside R solution in dilute sulphuric acid R and 4 g of sulphamic

acid R. Make alkaline with concentrated ammonia R, added dropwise until all the

sulphamic acid has dissolved. Addition of an excess of concentrated ammonia R

produces a violet colour, turning to violet-blue:

CH3

CH COO-

OH

CH3

C

O

H

Na2[Fe(CN)

5NO]

CH3

CO

HNa

2[Fe(CN)

5C

O

H]

[O], H+

+ CO2

CH2 2. Reactions of Na

+.

Non-Pharmacopoeial reactions:

a) forming of pentabromacetone:

C

CH3

CH3

O C

CHBr2

CBr3

O

CH2

C

CH2

OH

COONa

COONa

COONa

CH2

C

CH2

OH

COOH

COOH

COOH

H+ KMnO4

- CO2

Br2

Acetone white

b) on heating a white precipitate develops, which and dissolves on cooling:

CH2

C

CH2

OH

COO

COO

COO

CH2

C

CH2

OH

COO

COO

COO

2

-

-

-

-

-

-

2

Ca3+ 3CaCl2

+ 6Cl-t0

Purity

Oxalates. Dissolve the substance in water, add hydrochloric acid and

granulated zinc. Heat on a water-bath. Add phenylhydrazine hydrochloride and to

boiling. Cool rapidly, add hydrochloric acid and potassium ferricyanide solution.

Any pink colour in the solution is not more intense than that in a standard.

109

Assay

1. Non-aqueous titration. Titrate with perchloric acid in the medium of

anhydrous acetic acid, indicator – naphtholbenzein. S=1/3.

2. Ion-exchange chromatography:

CH

2

C

CH2

OH

COOH

COOH

COOH

CH2

C

CH2

OH

COONa

COONa

COONa

[Kat(H+)]

Citric acid is neutralised with an alkali; s=1/3:

CH

2

C

CH2

OH

COONa

COONa

COONa

CH2

C

CH2

OH

COOH

COOH

COOH

+ 3NaOH + 3H2O

3. Back argentometry by Volhard method; s=1/3:

CH

2

C

CH2

OH

COONa

COONa

COONa

CH2

C

CH2

OH

COONa

COONa

COONa

+ 3AgNO3 + 3NaNO3

AgNO3 + NH4SCN + NH4NO3AgSCN

FeNH4(SO4)2 + 3NH4SCN Fe(SCN)3 + 2(NH4)2SO4

Usage It is used for containing of blood.

Storage Store in an air-tight container.

Sodium hydrogen citrate (Natrii hydrocitras pro injectionibus)

CH

2

C

CH2

OH

COONa

COONa

COOH . H2O1,5

Disodium hydrogen 2-hydroxypropane-1,2,3-tricarboxylate sesquihydrate

Identification, assay, usage and storage – see sodium citrate.

+ HClO4

CH3COOH

+ NaClO4

CH2

C

CH2

OH

COONa

COONa

COONa

CH2

C

CH2

OH

COOH

COOH

COOH

3 3

110

Chapter 10. MEDICINAL SUBSTANCES WHICH ARE

DERIVATIVES OF ALIPHATIC AMINO ACIDS

Plan

1. General characteristic of aminoacids.

2. Medicinal substances, which are the derivatives of aliphatic amino acids.

Amino acids are derivatives of carboxylic acids, which contain in their

molecules one or more amino groups. -Amino acids are structural elements of

proteins and commonly occur in nature. More than 20 -amino acids have been

obtained from hydrolysates of proteins. They have general formula:

CH NH2

R

COOH

Amino acids can be divided into 2 groups:

-«Non-essential» amino acids can be synthesised by living organism in enough

quantities for supplement of normal functions;

-«Essential» amino acids – which are not synthesised by living organism or

synthesised in not enough quantities and have to be obtained with the food.

-Amino acids (except the simplest glycine H2N-CH2-COOH) exist in

optically active forms. Aliphatic aminoacids are soluble in water and non-soluble in

organic solvents. All aminoacids are amphoteric compounds due to acidic group (-

COOH) and basic group (-NH2). They can form salts with acids and bases.

R CH C

NH3

OH

O

R CH C

NH2

OH

O

R CH C

ONa

O

NH2

+

-ClHCl NaOH

- H2O

Aminoacids are amphoteric electrolytes; they exist as dipole ions in water

solutions and in solid condition.

Aminoacids are classified to -, -, - etc. in dependence of disposition of

carboxylic and aminogroup and have different chemical properties.

Heating:

-aminoacids form 2,5-diketopiperazines by intermolecular condensation:

R CH

C

NH2

OH

O

RCH

C

NH2O

OH

NH

NHR

R

O

O

tO

- 2H2O

111

-aminoacids loose a molecule of ammonium and become unsaturated

aminoacids:

R CH C

NH2

OH

O

R CH

CH

COOHt

O

- NH3

- aminoacids form lactams by intramolecular cyclization:

R CH CH2

CH2

C

O

OH

NH2

NH

R

O

tO

- H2O

Reaction with copper sulphate:

- aminoacids form very stable blue complex salts:

R CH C

NH2

OH

O

R CH C O Cu O C CH R

NH2

NH2

O

O

CuSO4

2

- aminoacids form coloured complexes but they are unstable.

- aminoacids do not react with copper sulphate.

Identification

All aminoacids form blue-violet colouring on heating with ninhydrin: O

O

O

R CH C

NH2

OH

O

O

OH

O

R C

O

H

. H2O + + + NH3 + CO2

t0

O

O

O

H N H

H

O

O

OH

OH

O

N

O

O

H4NO

O

N

O

O

+ +- H2O

NH3

112

Assay

1. Determination of nitrogen by sulphuric acid digestion (Kjeldahl method)

– detection of nitrogen in organic compounds is required by Pharmacopoeia for many

substances of this group. This method consist of two stages:

a) mineralization of organic substance (boiling in the special apparatus in

the presence of K2SO4, CuSO4 and conc. H2SO4);

R CH C

NH2

OH

O

H2SO

4

CO2 + H

2O + NH

4HSO

4

[O]

Then 30% NaOH solution is added:

NH4HSO4 + 2NaOH NH3 + 2H2O + Na2SO4

The educed ammonium gets into the flask with hydrochloric acid. Titrate the

distillate with 0.01 M sodium hydroxide, using methyl red solution as indicator.

b) acid-base titration:

NH3 + HCl NH4Cl

HCl + NaOH NaCl +H2O.

excess

Repeat the test using about 50 mg of glucose in place of the substance to be

examined (n2 - volume of 0.01 M sodium hydroxide in the blank, ml; n1- volume of

0.01 M sodium hydroxide in the test, ml).

.

)(01401,0,% 12

m

nnN

2. Formol titration (the non-Pharmacopoeial method).

Formalin neutralised by phenolphthalein is added into amino acid solution. N-

methylene derivative with free carboxyl is formed, which then is titrated with an

alkali:

H

COONa

CH2

COOC CHR

N

+

NaOH

2O

O

H

H H+

+ +R RCH COOH

NN CH2

CH2

CH2OH

R CH COOH

NH2

The titration of -aminoacids is difficult, because they exist as intramolecular

salts.

3. Acid-base titration in non-aqueous solvents.

Usage of amino acids in medicinal practice is based on their ability to take part

in the synthesis of proteins, hormones, peptides and ferments.

113

Glutamic acid (Acidum glutaminicum)

C CH2

CH2

C C

O

OH OH

ONH2

(2S)-2-aminopentanedioic acid

Glutamic acid is the structural element of many proteins: myosin, casein, -

lactoglobulin etc.; proteins of brain and cereals contain it in large quantities.

Preparation By interaction of acetylaminomalonic ester with acrylonitril:

C

C

C

OC2H

5O

NHCOCH3

O OC2H

5

H

CH2

CH CN

CN

C

C

C

OC2H

5O

NHCOCH3

O OC2H

5

CH2

CH2

CN

C

C

C

OHO

NH2

O OH

CH2

CH2

C

CH

CH2

OHO

NH2

CH2

C

O

OH

CN

C

C

OHO

NH2

CH2

CH2

H2O

- CO2

H2O

Properties A white, crystalline powder or colourless crystals, freely soluble in

boiling water, slightly soluble in cold water, practically insoluble in acetic acid, in

acetone, in alcohol and in ether.

Identification

1. Specific optical rotation.

2. IR-spectrum.

3. Thin-layer chromatography. Ninhydrin is used as the solution for

detection (see non-Pharmacopoeial reactions).

NH2

NH2

OH OH

C

O

O

COH

+ NaOH

C

O

ONa

C

O

+ H2O

4. To the solution of substance add phenolphthalein and sodium hydroxide

to change the colour of the indicator to red. Add a mixture of formaldehyde solution,

carbon-dioxide-free water and phenolphthalein, to which sufficient sodium hydroxide

has been added to produce a pink colour. The solution is decolourised. Add sodium

hydroxide until a red colour is produced. The total volume of sodium hydroxide used

4.0 ml to 4.7 ml.

114

Non-Pharmacopoeial reactions:

- melting with resorcinol in the presence of conc. H2SO4. This red coloured

product after adding of water and ammonium solution gets red-violet with green

fluorescence:

C CH2

CH2C C

O

OH OH

ONH2

NH

O

C

OH

O

tO

- H2O

NH

O

C

OH

O

H

OHOH

H

OH OH

NH

C

OH

O

O OHOH

t OH2SO4,

- 2 H2O

NH4OH

ONH4

O

C

NH2

O OOH

C

NH2

ONH4

O

OH

O OHOH- H2O

- with CuSO4 in alkaline medium – dark-blue copper complex (see

description).

Assay

1. Alkalimetry. Titrate with sodium hydroxide, using bromothymol blue as

indicator until the colour changes from yellow to blue; s=1;

NH2 NH

2

OH OH

C

O

O

COH

+ NaOH

C

O

ONa

C

O

+ H2O

2. Determination of nitrogen by sulphuric acid digestion (Kjeldahl

method).

3. Formol titration; s=1/2.

115

NH2

OH OH

C

O

O

CONa

+ NaOH

C

O

OHN

C+

O

HCOH CH2

C

O

ONa

NC

OO

CH2

Na

Usage In medicine glutamic acid is usually used for treatment of CNS-

diseases, epilepsy psychoses, reactive conditions and in paediatrics.

Storage In well-closed containers, protected from light.

Меthionine (Methioninum)

(2S)-2-amino-4-(methylsulphanyl)butanoic acid

Blood proteins, protoplasm, albumin and casein contain methionine.

Preparation Methionine is obtained by condensation of acetylaminomalonic

ester and β-methylthioethanol with further hydrolysis of the intermediate product:

Properties A white or almost white, crystalline powder or colourless crystals,

soluble in water, very slightly soluble in alcohol, practically insoluble in ether.

Identification

1. Optical rotation.

2. IR-spectrum.

3. Thin-layer chromatography; then ninhydrin is used as solution for

detection.

4. The substance and glycine dissolve in dilute sodium hydroxide solution.

Add solution of sodium nitroprusside and heat. Add phosphoric and hydrochloric

acids a dark-red colouring appears:

H2S + Na2[Fe(CN)5NO] Na2H2[Fe(CN)5NOS]

COOC2H5

HC

COOC2H5

NHCOCH3

HOCH2CH2SCH3CH3 S CH2CH2 C NHCOCH3

COOC2H5

COOC2H5

H2O

CH3 S CH2CH2 CH COOH

NH2

+ CO2 + CH3COOH + 2C2H5OH

CH3 S CH2CH2 CH C

O

NH2OH

+ N a 2 S + C H 3 O H + 2 N H 3 + 2 H O C H 2 C H 2 C H C O O N a

O H

H 3 C S N a

t + 5 N a O H

S C H 2 C H 2 C H C O O H

N H 2

2 C H 3

116

Non-Pharmacopoeial reactions:

- after acidifying of the product melted the smell of mercaptan and hydrogen

sulphide appears:

Na2S + H3CSNa + 2H2SO4 H2S + CH3SH + Na2SO4 + NaHSO4

- with СuSO4 in the presence of sodium acetate a lilac-blue precipitate is

formed.

Assay

1. Non-aqueous titration. Dissolve the substance in anhydrous formic acid,

add anhydrous acetic acid. Titrate with perchloric acid. The end-point is stated by

potentiometric method; s=1.

CH3-S-CH2-CH2-CH-COOH + HClO4

HCOOH

NH2NH3

CH3-S-CH2-CH2-CH-COOH ClO4

2. Determination of nitrogen by sulphuric acid digestion (Kjeldahl

method).

3. Iodometry in the medium of phosphate buffer and in the presence of

potassium iodide. The excess of iodine is titrated with Na2S2O3. (The indicator is

starch). S=2.

4. Iodine monochloride titration (iodchlorimetry); the indicator is starch.

S=1.

5. Formol titration. S=1.

Usage For treating and prevention of liver diseases and toxic defeats.

Storage Store in a well-closed container, protected from light.

Aminalon (Aminalonum)

Acidum γ-aminobutyricum

Preparation By alkaline hydrolysis of pyrrolidone-2:

S CH2CH2 CH

NH2

H3C COOH + ICl + H2O

S CH2CH2 CH

NH2

H3C COOH

O

+ HI + HCl

ICl + HI I2 + HCl

I2 + 2Na2S2O3 2NaI + Na2S4O6

H2N CH2 CH2 CH2 COOH

C2H5OH

CH3COOHCOOK

CH2

CH2 CH2 NH2

C2H5OH

KOH

N

H

OCH2

CH2 CH2 NH2

COOH

117

Properties White crystalline powder with a weak specific odour, hydroscopic.

Freely soluble in water.

Identification 1. The reaction with ninhydrin.

2. The substance analized educes hydrogen sulphide on melting with

potassium thiocyanate. H2S is detected with the lead paper.

3. Ammonium is educed by heating and then crimson colouring with

alloxan appears:

Optical density of this coloured product is detected at =526 nm.

Assay

1. Non-aqueous titration. Titrate with perchloric acid in the medium of

anhydrous acetic acid; s=1.

2. Determination of nitrogen by sulphuric acid digestion (Kjeldahl’s

method).

3. Formol titration. S=1.

Usage Neurotropic.

Storage In well-stoppered bottles.

Cysteine hydrochloride (Cysteini hydrochloridum)

CH-NH2

CH2-SH

COOH

. HCl

(2R)-2-amino-3-sulfanylpropanoic acid hydrochloride

COOH

CH2

CH2

CH2

NH2

+ HClO4

CH3COOH

COOH

CH2

CH2

CH2

N H

H

H+

. ClO4-

NH3

N

NH

O

OO

H

OHN

N

O

OO

H

OHHClN

N

O

OO

H

OHHHN

N

O

O

OO

H

HN

N

O

OO

H

N

N

O

H

N

H4NO O

H

118

Preparation Homocystine is reduced by hydrogen in the presence of catalysts:

S-CH2-CH-COOH

S-CH2-CH-COOH

NH2

NH2

CH-NH2

CH2-SH

COOH

CH-NH2

CH2-SH

COOH[H]

Zn2

HCl. HCl

Properties A white, crystalline powder or colourless crystals, freely soluble in

water, slightly soluble in alcohol.

Identification

1. Specific optical rotation.

2. IR-spectrum.

3. Thin-layer chromatography (the detector is ninhydrin).

4. Dissolve the substance in water, add dilute sodium hydroxide solution

and sodium nitroprusside solution. A yellow colour develops which becomes red.

5. The reaction of chlorides.

Non-Pharmacopoein reactions:

-mix the substance with conc. H2O2 solution, and with FeCl3 solution. Cool,

add dilute hydrochloric acid and barium chloride solution - a white precipitate forms.

(oxidise to sulphate and precipitate with BaCl2 is formed).

-the reaction with copper sulphate (black precipitate).

-the reduction of phosphorwolframic acid (blue colouring).

-the reaction with FeCl3- blue colour is formed.

Assay

1. Iodometry. Dissolve the substance in dilute hydrochloric acid, cool and

add potassium iodide and 0.05 M iodine solution. Titrate with sodium thiosulphate,

using starch solution as indicator. Carry out a blank titration. S=2.

2. Determination of nitrogen by H2SO4 digestion (Kjeldahl method).

3. Formol titration. S=1.

4. Alkalimetry. S=1.

5. Argentometry. S=1.

Usage For treating cataract; for electrophoresis (5% aqueous solution).

Storage In well-closed containers, protected from light.

+ I22 S CH2 CH COOH

NH2

COOHCHCH2S

NH2

COOH

CH NH2

CH2 SH

+ 2HI

119

Acetylcysteine (Acetylcysteinum)

HC COOH

NH CH3

O

HSCH2

(2R)-2-(acetylamino)-3-sulfanylpropanoic acid

Calculated with reference to the dried substance.

Properties A white, crystalline powder or colourless crystals, freely soluble in

water and in alcohol, practically insoluble in methylene chloride.

Identification

1. The specific optical rotation.

2. Melting point: 104 °C to 110 °C.

3. IR spectrophotometry.

4. Thin layer chromatography.

5. With sodium nitroprusside solution and concentrated ammonia a dark

violet colour develops.

Assay Iodometry. Titrate with 0.05 M iodine solution, using starch solution as

indicator; s=2:

HC COOH

NH CH3

O

HSCH2

HC COOH

NH CH3

O

SCH2

SCH2

CH

NH

O

H3C

2 + I2 HOOC + 2 HI

Storage Store protected from light.

Usage Mucolytic; antidote for paracetamol poisoning.

Sodium calcium edetate 10% solution for injections

(Solutio tetacini calcii 10% pro injectionibus)

Disodium [(ethylenedinitrilo)tetra-acetato]calciate(2-)

Properties A white or almost white powder, hygroscopic, freely soluble in

water, practically insoluble in alcohol and in ether.

CH2

N

CH2COONa

CH2COO

Ca

CH2COO

CH2COONaN

CH2

120

Identification

1. IR-spectrum.

2. Dissolve the substance, add lead nitrate solution and potassium iodide

solution. No yellow precipitate is formed. Make alkaline to red litmus paper by the

addition of dilute ammonia, add ammonium oxalate solution – a white precipitate is

formed.

CH2

CH2

N

N

CH2COO

CH2COO

CH2COONa

CH2COONa

Ca + Pb(NO3)2 Ca(NO3)2+

CH2

CH2

N

N

CH2COO

CH2COO

CH2COONa

CH2COONa

Pb

Ca(NO3)2 + (NH4)2C2O4CaC2O4 + 2NH4NO3

Dissolve the substance. Make alkaline to red litmus paper by the addition of

dilute ammonia, add ammonium oxalate solution – at most, a slight precipitate is

formed.

3. Ignite. The residue gives reactions of Ca2+

.

4. Reactions of Na+

.

The non –Pharmacopoeial reaction: add the substance into the mixture of

FeCl3 and NH4CNS –a colouring gets yellow.

Assay Dissolve the substance, add hexamethylenetetramine and hydrochloric

acid. Titrate with lead nitrate. (Indicator – xylenole orange triturate). S=1.

CH2

CH2

N

N

CH2COO

CH2COO

CH2COONa

CH2COONa

Ca + Pb(NO3)2 Ca(NO3)2+

CH2

CH2

N

N

CH2COO

CH2COO

CH2COONa

CH2COONa

Pb

Usage Chelating substance, used in treatment of lead poisoning.

Storage In a well-closed container.

121

Chapter 11. MEDICINAL SUBSTANCES DERIVATIVES OF

ETHERS AND ESTERS

Plan

1. General characteristic of ethers.

2. Medicinal substances derivatives of aliphatic and arylaliphatic ethers – ether,

diphenhydramine hydrochloride (dimedrolum); Preparation, identification and purity,

methods of quantitative definition, usage and storage.

3. General characteristic of esters of mineral acids.

4. Medicinal substances of mineral acid esters – glycerol trinitrate solution,

pentaaerythrityl tetranitrate, calcium glycerophosphate, phytinum, busulfan;

Preparation, identification and purity, methods of quantitative definition, usage and

storage.

5. Medicinal substances derivatives of esters of arylaliphatic acids.

Ethers are organic compounds with general formula: R – O – R'.

The lower ethers are very volatile liquids with the characteristic odour. On the

air or by influence of oxidisers they easy form various explosive peroxides and

hydrogen peroxides. It is necessary to take into consideration during Preparation,

storage, analysis and usage.

Pharmacopoeial medicines from the group of ethers are: ether and

diphenhydramine.

Medicinal substances derivatives of ethers

Ether (Aether)

Ether, anaesthetic (Aether anaestheticus)

C2H5 – O – C2H5

Preparation On heating a mixture of ethyl alcohol and concentrated sulphuric

acid to 135o C:

C2H5OH + S

HO

HO

O

OS

O

O

HO

H5C2O

+ H2O

S

O

O

HO

H5C2O

+ C2H5OH H5C2 O C2H5 + H2SO4

It is necessary to support the optimal temperature regimen (130-140C) for the

maximum yield because of forming side products, which can be divided according to

their chemical properties into 4 groups:

- acids (CH3COOH, H2SO3 and H2SO4);

- peroxides (hydrogen peroxide, dioxyethyl peroxide, oxyethyl

hydroperoxide, ethylidene peroxide);

- unsaturated compounds (ethylene, vinyl alcohol);

122

- aldehydes (acetaldehyde).

During storage of diethyl ether (especially at inappropriate conditions) under

light and oxygen action analogous side products are formed. Diethyl ether can

contain impurities of water and ethyl alcohol.

During analysis of diethyl ether, storage and working with it, it is necessary to

keep safety precautions (Inflammable! Explosive!).

There are 2 substances in Pharmacopoeia, which differs by their purity: ether

and anaesthetic ether (Aether anaestheticus).

Properties A clear, colourless, very mobile, highly flammable, volatile liquid.

Soluble in 15 parts of water, miscible with alcohol and fatty oils.

Vapours of ether form the explosive mixture in certain proportions with air,

oxygen and nitrogen protoxide.

Identification

1. Relative density (0.714-0.716).

2. Test for distillation range (it distils completely between 34.0C and 35.0C).

Purity

1. Acids (detected with bromothymol blue).

2. Acetone and aldehydes are determined with alkaline potassium

tetraiodomercurate solution (Nessler reagent). The lower layer shows only a slight

opalescence (for anaesthetic ether) and it may show yellow or reddish-brown

opalescence but not grey or black opalescence (for ether):

CH3C

O

H

+ K2[HgI4] + 3KOH Hg + CH3COOK + 4KI + 2H2O

3. Peroxides (add KI and starch solutions – no colour is produced):

H5C2 – O – O – C2H5 + 2KI + H2O I2 + H5C2 – O –C2H5 + 2KOH;

In the substance the side smell and non-volatile residue are determined.

Usage As a solvent for tinctures, extracts and some other external medicines; it

is used in analytical practice. Ether is very limited used as an anaesthetic medicine.

Storage Store in an airtight container, protected from light, at the temperature

of 8C to 15C. The contents of a partly filled container may deteriorate rapidly.

Diphenhydramine hydrochloride (Dimedrolum)

CH O CH2

CH2 N

CH3

CH3

H5C6

H5C6

. HCl

2-(Diphenylmethoxy)-N,N-dimethylethanamine hydrochloride

Preparation Interaction of benzhydrol and β-dimethylamine ethyl chloride

hydrochloride in the presence of alkali:

123

Cl CH2

CH2 N

CH3

CH3

CH OH CH O CH2

CH2 N

CH3

CH3

CH O CH2

CH2 N

CH3

CH3

+ . HCl

H5C6

H5C6

NaOHH5C6

H5C6

HCl

H5C6

H5C6

. HCl

Properties A white or almost white, crystalline powder, very soluble in water,

freely soluble in alcohol, practically insoluble in ether.

Identification

1. Melting point (168˚С -172˚С).

2. UV-spectrum.

3. IR-spectrum.

4. With conc. H2SO4 - an intense yellow colouring develops.

CH O CH2

CH2 N

CH3

CH3

CH O CH2

CH2 N

CH3

CH3HH

H5C6

H5C6

. HCl

conc.H2SO4H5C6

H5C6

HCl

+ +

SO4 +2-

It becomes red by the addition of HNO3. Then water and chloroform are added,

and an intense violet colour develops in the chloroform layer.

5. Reactions of chlorides.

The non-Pharmacopoeial reaction: acidic hydrolysis.

Melting point of the benzhydrol formed after recrystallising is 62-67˚C.

CH O CH2

CH2 N

CH3

CH3

CH OH OH CH2

CH2 N

CH3

CH3

H5C6

H5C6

. HCl

to

, HCl, H2OH5C6

H5C6

+ . HCl

Assay

1. Alkalimety. Dissolve the substance in alcohol, add 5.0 ml of hydrochloric

acid Carry out a potentiometric titration, using 0.1 sodium hydroxide solution. Read

the volume added between the 2 points of inflexion; s=1.

HCl + NaOH NaCl + H2O H

5C

6

CHH

5C

6

O CH2CH

2N

CH3

CH3

H5C

6

CHH

5C

6

O CH2CH

2N

CH3

CH3

. HCl + +

C2H5OH

NaOH NaCl+H2O

2. Non-aqueous titration.

The substance is titrated with perchloric acid in the medium of anhydrous

acetic acid in the presence of (CH3COO)2Hg till blue-green colouring. Indicator-

crystal violet solution; s=1. Carry out a blank titration.

124

CH O CH2

CH2 N

CH3

CH3

CH O CH2

CH2 N

CH3

CH3H

H5C6

H5C6

. HClCH3COOH

H5C6

H5C6

HgCl2 + 2CH3COOH+

ClO4 + -

2 + 2HClO4 + (CH3COO)2Hg

2.

3. Back iodchlorimetry using starch solution as an indicator; s=1.

CH O CH2

CH2 N

CH3

CH3

CH O CH2

CH2 N

CH3

CH3

H5C6

H5C6

. HCl

ICl H5C6

H5C6

HCl. . ICl

IСl + KI I2 + KCl

I2 + 2Na2S2O3 2NaI + Na2S4O6

4. Back argentometry by Volhard method; s S=1.

Usage Histamine H1-receptor antagonist.

Storage In well-closed containers, protected from light.

Medicinal substances of mineral acids esters

Esters of mineral acids can be determined as oxyacids that have an atom of

hydrogen substituted by an organic radical.

1% Glycerol trinitrate solution (Solutio Nitroglycerini 1%)

Propane-1,2,3-triyl trinitrate Preparation It is prepared by slowly addition of glycerol into an ice cooled

(–15o C) mixture of conc. H2SO4, and HNO3:

Properties A clear, colourless or slightly yellow solution. Miscible with

acetone and with ethanol. Practically insoluble in water, freely soluble in ethanol.

Identification

1. IR-spectrum.

CH2

CH

CH2

O

O

O

NO2

NO2

NO2

CH2

CH

CH2

OH

OH

OH

+ 3HNO3H2SO4 + 3H2O

C H 2 O N O 2

C H

C H 2

O

O

N O 2

N O 2

125

2. Thin-layer chromatography.

3. It complies with the limits of assay.

4. Non-Pharmacopoeial reactions:

a) reaction with diphenylamine. A blue colouring appears.

b) reaction of glycerol-residue after saponification on heating with KHSO4.

Assay

1. Test solution. Prepare a solution of the substance in methanol.

Reference solution. Dissolve sodium nitrite in methanol.

Into 3 flasks introduce 10 ml of the test solution, 10 ml of the reference

solution and 10 ml of methanol as a blank. To each flask add dilute sodium hydroxide

solution, mix and allow to stand for 30 min. Add sulphanilic acid solution and dilute

hydrochloric acid. After exactly 4 min read the absorbance of the test solution and the

reference solution at 540 nm using a blank titration as a compensation liquid.

Calculate the amount of glyceryl trinitrate in mg in the test solution from the

follow expression:

1008.60

TR

sT

mA

CmA

AT = absorption of the test solution,

mT = mass of the substance to be examined, in milligrams,

C = percentage content of sodium nitrite used as reference,

Ar = absorption of the reference solution,

mS = mass of sodium nitrite, in milligrams. CH2ONO2

CHONO2

CH2ONO2

+ 5NaOH CH3COONa + HCOONa + 2NaNO2 + NaNO3 + 3H2O

NH2

SO3H

NaNO2

HCl

SO3H

N N

Cl

NHCH2CH2NH2

NHCH2CH2NH2

N=N SO3H

2. Nitrate is determined by colorimetry (it is based on interaction with phenol-

2,4-disulphonic acid). The concentration of glycerol is stated by calibration diagram:

(NH4

+)3

OO

N SO3

SO3

O3NH4OH

OH

SO3H

SO3H

O2N

CH3COOH

KNO3

OH

SO3H

SO3H

. H S O 4 - +

N N

H

H 2 S O 4

N O 3 -

N O 3 -

2 N H N H N H

126

3. Reaction of saponification (in the presence of H2O2 to avoid reducing

processes). S=1/5.

The excess of alkali titrated with HCl solution by phenolphthalein. A blank

titration is carried out.

4. Alkalimetry in the medium of pyridine. Titrate with dibutylammonium

hydroxide. End-point is stated by potentiometry. S=1/3. H2C O-NO2

HC

H2C O-NO2

O-NO2 + 3[(C4H9)4N]OH

H2C OH

HC

H2C OH

OH + 3[(C4H9)4N]NO3ï ³ðèäèí

Usage Antispasmodic. It is used for treatment certain diseases of the heart.

Storage Store dilute solutions protected from light, at a temperature of 2C to

15C.

The substance must be cautiously proposed and kept because of its explosive

properties.

Pentaaerythrityl tetranitrate (Erynitum)

2,2-bis(hydroxymethyl)propane-1,3-diol trinitrate

Preparation Esterification of pentaaerytithritol with HNO3:

Properties A white or slightly yellowish powder, soluble in acetone, slightly

soluble in alcohol, practically insoluble in water.

Identification

1. Melting point138-142 oС.

2. IR-spectrum.

3. Thin-layer chromatography.

4. Non-Pharmacopoeial reactions:

a) reaction for nitrates after hydrolysis (with diphenylamine).

b) after hydrolysis pentaaerytritol interacts with benzoyl chloride and forms

pentaaerythritil benzoate with melting point 99-101oС.

C3H5(ONO2)3 + 5NaOH NaNO3 +2NaNO2 + CH3COONa + HCOONa + 3H2OH2O2

4C3H5(ONO2)3 6N2 + 12CO2 + O2 +10H2O

C

CH2 O NO2

CH2 O NO2

H2C

H2C

O

O

O2N

O2N

C

CH2 O NO2

CH2 O NO2

H2C

H2C

O

O

O2N

O2NH2SO4

+ 4HNO3C

CH2OH

CH2OH

HOH2C

HOH2C+ 4H2O

Pyridine

127

Assay For the substance is the liquid chromatography.

For tablets is gravimetry. To take into account the contents of stearic acid

(titration with an alkali in the dimethylformamide or acetone medium - see glyceryl

trinitrate).

Usage Spasmolytic.

Storage Protected from light and heat. Explosive!

Calcium glycerophosphate (Calcii glycerophosphas)

Preparation Esterification of glycerol with excess of sodium monophosphate

in the presence of H2SO4. The formed diglycerophosphates are hydrolysed with

alkali. Calcium glycerophosphate is precipitated with calcium acetate in the presence

of alcohol.

Properties A white powder, hygroscopic, sparingly soluble in water, practically

insoluble in alcohol.

Identification 1. Mix with potassium hydrogen sulphate, heat and direct the white vapour

towards a piece of filter paper impregnated with a freshly prepared solution of

sodium nitroprusside – develops a blue colour in contact with piperidine.

2. Ignite and carry out reaction of phosphates with molybdovanadic reagent

– a yellow colour develops:

Reactions of Ca2+

.

Non-Pharmacopoeial reactions:

a) reaction of glycerophosphoric acid:

CaPO3 O C3H5(OH)2 nH2O.

CH2

CH

CH2

OH

OH

O P O

O

O

Ca

H 3 P O 4 + 1 2 ( N H 4 ) 2 M o O 4 + 2 1 H N O 3 ( N H 4 ) 3 P O 4 . 1 2 M o O 3 + 2 1 N H 4 N O 3 + 1 2 H 2 O

CH2

CH

CH2

OH

OH

O P

O

O

O Ca

+ (CH3COO)2Pb

CH2

CH

CH2

OH

OH

O P

O

O

O Pb

+ (CH3COO)2Ca

white precipitate

CH2

CH2 OH

O

OH

P

Ca

O

CH

O

O + 2HNO3+ H2O

t o

CH2

CH2 OH

O

OHCH

H

H3PO4Ca(NO3)2

+ +

128

b) reaction of glycerol (on heating with KHSO4 the smell of acrolein appears).

Assay Compexonometry; s=1.

Usage For hypotrophy, rachitis and disfunction of nervous system.

StorageIn well-stoppered bottles.

Phytinum

Phytinum occurs in various plants: pea, lentil, hemp, potato etc. It is the

mixture of calcium and magnesium salts of inositol phosphoric acids, mainly of

inositol hexaphosphoric acid:

It is obtained from the scarps during producing of vegetable oil and starch. The

solution is purified from proteins and neutralised with NH4OH or Na2CO3 – insoluble

phytinum is educed. By adding of HCl this precipitate becomes soluble acidic salt

and then precipitated with ethanol as the soluble in water phytinum.

Identification

1. Reactions of Ca2+

in solution of acetic acid.

2. Reactions of phosphoric acid.

Assay It is based on interaction of phytinum with copper sulphate solution:

copper sulphate is detected by iodometry after reducing copper salt of inositol

phosphoric acids (indicator - starch). S=1.

Carry out a blank titration.

Calculate on P2O5 .

Usage Phytinum is the stimulant of blood-forming processes; it is used at low

concentrations of phosphorus in organism and improves functions of central nervous

system.

Storage In well-stoppered bottles.

(HO)OPO

OMg

O

OPO(OH)2OPO(OH)2

CaOO

OPO(OH)

OPO(OH)

OPO(OH)

I2 + 2Na2S2O3 2NaI + Na2S4O6

2CuSO4 + 4KI Cu2I2 + 2K2SO4 + I2

CH2

CH2 OH

O

OH

P

Ca

O

CH

O

O + KHSO4CaHPO4

-

CH2

CH2 OHO

CH

OSO3K

OSO3K

C

CH

CH2

Ht

o

129

Busulfan (Myelosanum)

Butane-1,4-diyl di(methanesulphonate)

Properties A white or almost white, crystalline powder, very slightly soluble in

water, freely soluble in acetone and acetonitrile, very slightly soluble in alcohol and

in ether. It melts at about 116C.

Identification

1. IR-spectrum.

2. Thin-layer chromatography.

3. Add sodium hydroxide to the substance. Heat until a clear solution is

obtained, add potassium permanganate solution. The colour changes to blue and

finally to green. Filter and add ammoniacal silver nitrate solution – a precipitate is

formed.

Add potassium nitrate and sodium hydroxide, mix and heat to fusion. After

adding dilute hydrochloric acid the solution gives reaction of sulphates (with barium

chloride).

4. The Non-Pharmacopoeial reaction: on heating with alcoholic alkali

alcohol solution the white precipitate forms:

Assay Alkalimetry. To the substance water is added; solution is shaken, boiled

under a reflux condenser for 30 min. Allow to cool. Titrate with sodium hydroxide

until a pink colour is obtained. Indicator – phenolphthalein; s=1/2.

Usage For treatment of leukaemia.

Storage In an airtight container, protected from light.

CH3SO2 O (CH2)4 O SO2 CH3NaOH

2CH3SO3Na + HO (CH2)4 OH

CH3 SO2 O (CH2)4 O SO2 CH3

H2O

tº2CH3SO3H + HO(CH2)4OH

CH3SO3H + NaOH CH3SO3Na + H2O

CH3 SO2 O (CH2)4 O SO2 CH3

CH3 S ONa

O

O

+ CH3OH Na2SO4 K2MnO4NaOH Na2MnO42KMnO4+ + + + H2O

CH3OH + 2KMnO4 3H C

O

H

+ 2MnO4+ 2KOH 2H2O+

H C

O

H

+ 2[Ag(NH3)2]NO3 + H2O HCOONH4+ 2Ag + NH3

+ 2NH4NO3

+

CH3SO2 O (CH2)4 O SO2 CH3NaOH

2CH3SO3Na + HO (CH2)4 OH

130

During working with the substance keep safety precautions (to avoid its action

on skin and mucous membrane).

Esters of arylaliphatic acids

Aprofene (Aprophenum)

-Diethylaminoethyl ester 1,1-diphenylpropionic acid hydrochloride

Preparation Interaction of diphenylpropionic acid and -diethylaminoethyl

chloride.

Properties White crystalline powder. Readily soluble in water, 95% alcohol

and chloroform. Soluble in acetone and benzol.

Identification

1. Reactions of Cl-.

2. Dissolve in conc. H2SO4 - a green-yellow colouring appears, that after

shaking of solution remains on the walls of the test-tube during several minutes.

3. 7 drops of K2Cr2O7 solution in H2SO4 solution add to the substance. The

test-tube cover with the paper, impregnated with sodium nitroprusside solution and 1

drop of piperidine; heat. The blue spot appears (reaction for methyl group, bonded

with tertiary nitrogen atom).

4. Reaction with hydroxylamine and FeCl3 (for ester group).

5. At addition of CuSO4 and NH4CNS solutions the brown precipitate appears.

6. Reaction with Marquis reagent (HCOH in conc. H2SO4) – a yellow colour

develops.

7. Evaporate the substance with conc. HNO3 and add KOH alcoholic solution -

a violet colour develops (reaction of 1,1-diphenylpropionic acid, formed during

hydrolysis):

8. After action of ammonium vanadate solution in conc. H2SO4 a green colour

developed becomes brown.

Assay

1. Non-aqueous titration in the presence of (CH3COO)2Hg (indicator is

crystal violet). Carry out a blank titration. S=1.

C

CH3

C OCH2 CH2 N

C2H5

C2H5

O

. HCl

C

CH3

C OCH2 CH2 N

C2H5

C2H5

O

H+

tºC

CH3

COOH + HO(CH2)2N

C2H5

C2H5

131

2. In solution for injections (Solutio Apropheni 1% pro injectionibus) and

in pills (Tabulettae Apropheni – 0,025) aprofene is determined by alkalimetry

(indicator is phenolphthalein). S=1.

3. Argentometry (Volhard method). S=1.

4. Mercurimetry. S=1.

Usage Cholinolytic, spasmolytic.

StorageIn well-stoppered bottles.

Adiphenine hydrochloride (Spasmolytinum)

-Diethylaminoethyl ester 1,1-diphenylacetic acid hydrochloride

Properties White crystalline powder, odourless. Freely soluble in water and in

alcohol, soluble in chloroform.

Identification

1. Hydrolysis:

Diphenylacetic acid gets into ether layer and then its melting point is detected.

2. Reactions of Cl-.

Assay

1. Non-aqueous titration in the presence of (CH3COO)2Hg. S=1.

2. Alkalimetry in the presence of organic solvent. S=1.

3. Argentometry (Volhard method). S=1.

Usage Cholinolytic, spasmolytic.

Storage In well-stoppered bottles, protected from light and humidity action.

CH C O

O

CH2CH2 N

C2H5

C2H5

. HCl

CH C O

O

CH2CH2 N

C2H5

C2H5tº

H2OCH C

O

OH

+ HOCH2CH2N

C2H5

C2H5

132

Chapter 12. AMIDATED DERIVATIVES OF CARBONIC ACID

AND DI-(β-CHLORETHYL)–AMINE DERIVATIVES

Plan

1. Amidated derivatives of carbonic acid:

а) general characteristic;

b) urethanes. Medicinal substances. Meprobamate: Preparation, identification

and assay, usage, storage.

c) acyclic ureides. Medicinal substances. Bromisoval: Preparation,

identification and assay, usage, storage.

2. Derivatives of di–(β-chlorethyl)–amine.

а) general characteristic;

b) medicinal substances, derivatives of di–(β-chlorethyl)–amine:

novembichinum: Preparation, identification and assay;

cyclopyhosphamide: Preparation, identification and assay Preparation;

sarcolysin: Preparation, identification and assay, usage and storage;

chlorambucil: Preparation, identification, assay, storage and usage.

Carbonic acid can form salts, esters, amides and other derivatives. For

medicine amides are very important because their derivatives are medicinal

substances.

This class of compounds includes urethanes and ureides (acyclic and cyclic).

There are two amides of carbonic acid:

1. Carbamic acid – the product of substitution one hydroxyl group by

aminogroup;

2. Carbamide or urea – the product of substitution two hydroxyl groups by

aminogroups (full amide).

Urethanes are esters of carbamic acid:

Ureides are acyl derivatives of urea or products of interaction with acids. They

can be cyclic and acyclic. Ureides are usually made by interaction of urea with

anhydrides, acyl chlorides, or (most commonly) esters of suitable organic acid:

From dicarboxylic acids there are derived ureido-acids and cyclic ureides:

R O C NH2

O

O C

NH2

NH C

O

COOH_

H2OHOOC

+O C

NH2

NH2

O C

NH2

NH C CH2R

O

_H2O

O C CH2R

OH

O C

NH2

NH2

HOOC

O C

OH

OH

O C

OH

NH2

O C

NH2

NH2

133

Hydrogens of methylene group in barbituric acid can be substituted by various

radicals. This ability is in the base of synthesis of such medicinal substances as

barbiturates with hypnotic effect.

Urethanes

General scheme of Preparation:

Chemical properties:

Meprobamate (Meprotanum)

2-methyl-2-propylpropane-1,3-diyl dicarbamate

Preparation By the scheme:

Properties A white or almost white amorphous or crystalline powder, slightly

soluble in water and in ether, freely soluble in 95% alcohol and in acetone.

Identification.

1. Melting point 104-108C.

2. IR-spectrum.

3. Add acetic anhydride and sulphuric acid. The melting point of diacetyl

derivative is 124 – 128С.

R OH + Cl C NH2

O

R O C NH2

O

+ HCl

H3C C CH2 CH2 CH3

CH2 O C

CH2 O C NH2

NH2

O

O

+ 2NaOHR O C NH2

O

1)

2) R O C NH2

O

2 + H2SO4 + 2H2O 2ROH + 2CO2 + (NH4)2SO4

ROH + NH3 + Na2CO3

tº

tº

H3C C CH2CH2CH3

CH2OH

CH2OH

+ 2Cl C

O

NH2 H3C C CH2CH2CH3

CH2

CH2

O

O

C

C

NH2

NH2

O

O

+ 2HCl

карбамоилхлоридcarbamoyl chloride

2-methyl-2-propylpropane diol-1,3 meprobamate

+O C

NH2

NH2

HOOCCH2

HOOC

_2H2O

O C

NH

NH

C

C

CH2

O

O

barbituric acid

134

4. Dissolve in alcoholic potassium hydroxide and boil under a reflux

condenser, add glacial acetic acid and solution of cobalt nitrate in ethanol. A deep-

blue colour develops.

Non-Pharmacopoeial reactions:

a) on heating with alkali NH3 appears, which is detected by the smell and the

wet red litmus paper gets blue.

b) on heating with dil. H2SO4 educes СО2 (Ca(OH)2 solution gets turbid):

Assay Determination of nitrogen by sulphuric acid digestion (see aminoacids).

Usage Anxiolytic (tranquilliser).

Storage In well-closed bottles.

H3C C CH2 CH2 CH3

CH2 O C

CH2 O C NH2

NH2

O

O

+ 4NaOHtº

H3C C CH2 CH2 CH3

CH2

CH2

OH

OH

+ 2NH3 + 2Na2CO3

+

Ca(OH)2 + CO2 CaCO3 + H2O

+ 2CO2 + (NH4)2SO4H3C C CH2 CH2 CH3

CH2

CH2

OH

OH

2H2OH3C C CH2 CH2 CH3

CH2 O C

CH2 O C NH2

NH2

O

O

+ H2SO4

+ 2 C H 3 C O O H H 3 C C C H 2 C H 2 C H 3

C H 2 O C

C H 2 O C

O

O

N H

N H

C O C H 3

C O C H 3

H 3 C C

O

O C H 3 C

O

+ 2 H 3 C C C H 2 C H 2 C H 3

C H 2 O C

C H 2 O C N H 2

N H 2

O

O

c . H 2 S O 4

C

CH2

CH2

CH2 O C NH2

O

CH2 O C NH2

O

H3C

CH3(CH2)2

(CH2)2H3C+ 4KOH C

CH2

C

O

CH2

O

H3C

(CH2)2H3C

OH

OHCo(NO3)2

CH2

CH2

H3C

(CH2)2H3C

OH

Co

HOCH3

C

135

Acyclic ureides

General scheme of synthesis

The bromoanhydride of α–bromoderivative of aliphatic acid obtain and then it

is interacts with urea.

Bromisoval (Bromisovalum)

N-(-bromoisovalerianyl)-urea

The product of condensation of urea with monobromoisovalerianic acid.

Preparation

Properties White crystalline powder with the bitterish taste and weak odour.

Very slightly soluble in water, soluble in ethanol.

Identification

1. On heating with alkali educes NH3 (the specific odour).

2. On heating with the mixture (H2O + conc. H2SO4) the irritant odour of

isovalerianic acid appears.

3. After adding of HCl in the solution Br- are detected.

The chloroform layer gets brown-yellow (free bromine).

R CH2 COOHPBr5

R CH COBr

Br

C O

H2N

H2NR CH C NH C NH2

Br O O

CH C NH C NH2

Br O O

CH

H3C

H3C

SO2N(Na)Cl + 2HCl C6H5C6H5 SO2NH2 + Cl2 + NaCl

2HBr + Cl2 Br2 + 2HCl

+ (NH4)2SO4 + CO2 + HBrCH

H3C

H3C

CH2 COOHH2O

H2SO4CH C NH C NH2

Br O O

CH

H3C

H3C

, tº

tºCH C NH C NH2

Br O O

CH

H3C

H3C

4NaOHCH

H3C

H3C

CH COONa

OH

+ 2NH3 + Na2CO3 + NaBr

CH C NH C NH2

Br O O

CH

H3C

H3C

CH

H3C

H3C

CH2COClPBr5

CH

H3C

H3C

CH

Br

C

O

Br

C OH2N

H2N

хлорангидрид изовалериановокислоты

бромангидрид бромизовалериановойкислоты

бромизовал

chloranhydride of isovalerianic acid bromanhydride of -bromisovalerianic acid

bromisoval

136

4. On heating with CuSO4 solution in alkaline medium a pink colouring

appears (or by adding of CuSO4 excess - a red-violet colour develops – biuret test).

Assay Back argentometry by Volhard method. Heat with an alkali (for

obtaining Br-). The excess of AgNO3 is titrated with NH4SCN (indicator is

NH4Fe(SO4)2). Carry out a blank titration. S=1.

NaBr + AgNO3 AgBr + NaNO3

AgNO3 + NH4SCN AgSCN + NH4NO3

3NH4SCN + NH4Fe(SO4)2 Fe(SCN)3 +2(NH4)2SO4

Usage Soft tranquilliser and hypnotic.

Storage In well-closed orange glass bottles.

Di-(β-chlorethyl)-amine derivatives

The general structure of these substances:

Where R can be aliphatic, aromatic or heterocyclic radical.

Di-(β-chlorethyl)-amine derivatives have alkylative properties. They can react

with the nucleophylic centres of protein molecules (nucleinic acids, ferments) with

oppressing of DNA and RNA synthesis and as the result – with blockade of cells

mitosis. The nuclei of tumour tissues and lymphoid tissues are very sensitive for the

action of these substances. This ability was in the base for creation of cytostatics.

Di-(β-chlorethyl)-amines can easily react with nucleoproteids of cells of

blood-forming tissues and so they oppress blood-forming process.

For the synthesis of these substances as the initial product are usually used

aminoderivatives (aliphatic, aromatic or heterocyclic) and then by β–chlorethanol or

ethylene oxide the oxyethyl group is added:

tº

CH C NH C NH2

Br O O

R NaOH R CH C ONa

OH O+ C O

H2N

H2N

R N

CH2CH2Cl

CH2CH2Cl

H2

O C NH C ONa

N N

Cu/2

CuSO4; NaOH

tºH2N C NH C NH2

O O

H2N C NH2

O

+HN C O

ClCH2 CH2OHR NH2 R N

CH2CH2OH

CH2CH2OH

H2N C NH2

O

NaOHNH3 + NH C O

137

Substitution of oxygroups by chlorine is carried out with thionyl chloride

[sulphur dichlorooxide (IV)]:

The nitrogen atom gives the basic character for the derivatives of di-(β-

chlorethyl)-amine. The medicinal substances of these group are bases or

hydrochlorides:

For identification of substances various reactions used: of aliphatic, aromatic

part of molecule bonded with di-(β-chlorethyl)-amine. The choice of reaction

depends on the structure of substance. General reaction for determining of di-(β-

chlorethyl)-amine are based on interaction with nicotinic acid and benzidine; with

diethylamide of pyridine carboxylic acid and other reagents. If the substance is the

salt (hydrochloride) – chloride-ion is detected with silver nitrate solution.

Novembichinum, sarcolysin, chlorambucil, cyclophosphamide are used in

oncology.

Novembichinum

Cl

CH2-CH

2-Cl

CH2-CH

2-Cl

H3C-CH-CH2-N. HCl

2-Chloropropyl-di-(β-chlorethyl)-amine hydrochloride

Preparation

Properties White powder, soluble in water and in alcohol, insoluble in ether.

Identification

1. With Dragendorff reagent (KBiI4 in KI + dil. H2SO4) the substance

forms an orange precipitate.

2. Reactions for Cl-.

R N

CH2CH2Cl

CH2CH2Cl

R N

CH2CH2Cl

CH2CH2Cl

. HCl

R N

CH2CH2Cl

CH2CH2ClR N

CH2CH2OH

CH2CH2OH

SOCl2

2-chlorpropyl-N-di(-oxyethyl)-amine

SOCl2

CH3

CHCl

CH2

NCH2CH2OH

CH2CH2OH

H2C CH2

OCH3

CHCl

CH2NH2

HClCH3

CH

CH2

NH

CH3

CHCl

CH2 N

CH2CH2Cl

CH2CH2Cl

HClCH3

CHCl

CH2 N

CH2CH2Cl

CH2CH2Cl

. HCl

propyleneimine 2-chlorpropylamine

2-chlorpropyl-N-di(-chlorethyl)-amine

138

Assay Back argentometry by Volhard method. Indicator is NH4Fe(SO4)2. S=1.

Usage For inhibition of pathological cell growth. To keep safety precautions

during the work with this substance, to avoid its action on skin and mucous

membrane.

Storage In well-stoppered bottles or ampules, in cool place.

Cyclophosphamide (Cyclophosphanum)

(2RS)-N,N-bis(2-chloroethyl)tetrahydro-2H-1,3,2-oxazaphosphorin-2-amine 2-

oxide

Preparation

Properties A white or almost white, crystalline powder, soluble in water,

freely soluble in ethanol, slightly soluble in ether.

Identification

1. Melting point (51C).

2. IR- spectrum.

3. Thin-layer chromatography.

4. After boiling with alkali Cl- are detected:

5. Non-Pharmacopoeial reactions:

a) the substance is heated with conc. H2SO4 then it is cooled and 20% NaOH is

added. On heating NH3 educed, the wet red litmus paper gets blue (reaction for amide

nitrogen);

b) the substance is heated with the mixture of conc. H2SO4 and HNO3 till the

oxides of nitrogen removed and the solution gets colourless. Then into this solution

(NH4)2MoO4 is added, intense yellow colour develops and in time the yellow

precipitate appears:

H3PO4 + 12(NH4)2MoO4+21HNO3(NH4)3PO4.12MoO3+21NH4NO3+12H2O

O

P

NH

O

N

CH2CH2Cl

CH2CH2Cl

. H2O

3 N H 4 S C N + N H 4 F e ( S O 4 ) 2 2 ( N H 4 ) 2 ( S O 4 ) + F e ( S C N ) 3

N H 4 N O 3 + A g S C N

+ A g C l

. H N O 3

C H 3

C H C l

C H 2 N

C H 2 C H 2 C l

C H 2 C H 2 C l

. H C l

C H 3

C H C l

C H 2 N

C H 2 C H 2 C l

C H 2 C H 2 C l

e x c . A g N O 3 + N H 4 S C N

+ e x c. . A g N O 3

пропаноламин3

ClCH2CH2N

ClCH2CH2POCl2 + HO (CH2) NH2

O

P

NH

O

N

CH2CH2Cl

CH2CH2Cl

-бис-( -хлорэтил)-амиддихлорангидрид фосфорной

циклофосфанN-di-(-chlorethyl)-amide

dichloranhydride of phosphoric acid

propanolamine

cyclophosphamide

139

Assay

Argentometry (Volhard method) after heating with an alkali. The excess of

AgNO3 is titrated with NH4CNS in the presence NH4Fe(SO4)2 as the indicator. S=2.

Usage Cytotoxic (cytostatic).

Storage Store in a well-closed container.

Sarcolysin (Sarcolysinum)

d,l-a-amino--[n-di-(-chloroethyl)-aminophenyl]-propionic acid

hydrochloride

Preparation

Properties White or slightly yellow powder. Freely soluble in water on

heating, soluble in methanol, slightly soluble in ethanol.

Identification

1. Reactions of Cl-:

C CH CH2 N

CH2CH2Cl

CH2CH2Cl

NH2O

HO

. HCl

CH2

CHNH2

COOH

N

CH2CH2Cl

CH2CH2Cl

. HCl

HClCH2

CHNH2

COOH

N

CH2CH2Cl

CH2CH2Cl

SOCl2

CH2

CHNH2

COOH

N

CH2CH2OH

CH2CH2OH

H2C CH2

OCH2 CH(NH2)COOHH2N

[H]NO2 CH2 CH(NH2)COOH

HNO3CH2 CH(NH2)COOH

NH3

HCNCH2 C

O

H

phenylacetaldehyd

e

phenylalanine

p-nitrophenylalanine

d,l,n-di-(-oxyethyl)-aminophenylalanine

AgNO3+ NH4SCN AgSCN + NH4NO3

NH4Fe(SO4)2+ 3NH4SCN Fe(SCN)3 + 2(NH4)2SO4

R N

C H 2 C H 2 C l

C H 2 C H 2 C l

+ 2 N a O H R N

C H 2 C H 2 O H

C H 2 C H 2 O H

+ 2 N a C l

N a C l + e x c . A g N O 3 A g C l + N a N O 3

140

2. On heating alcoholic solution of the substance with ninhydrin solution a

violet colour develops.

3. The solution of substance is heated with solution of K2Cr2O7 in H2SO4.

The test-tubes covered with the paper impregnated with sodium nitroprusside

solution with 1 drop of piperidine – the blue spot appears (acetaldehyde):

R-CH2-CH2-Cl R-CH2-CH2-OHK2Cr2O7,t

o

H2SO4

R-CO

H

Assay

Argentometry (Volhard method) after heating with the excess of silver nitrate

solution. S=1/3.

COOH

CHNH2

H2C N

CH2CH2Cl

CH2CH2Cl

+ 3AgNO3 + 2H2Oto

COOH

CHNH2

H2C N

CH2CH2OH

CH2CH2OH

HCl

+ 3AgCl + 3HNO3

excess AgNO3 + NH4SCN AgSCN + NH4NO3

FeNH4(SO4)2 + 3NH4SCN Fe(SCN)3 + 2(NH4)2SO4

Usage Cytotoxic (cytostatic).

Storage In well-closed orange glass containers in cool dry place.

Chlorambucil (Chlorbutinum)

4-4-[di(2-chloroethyl)amino]phenylbutyric acid

N

CH2CH2Cl

CH2CH2Cl

CH2CH2CH2C

O

HO

.

141

Preparation

Properties A white, crystalline powder, practically insoluble in water, freely

soluble in alcohol and in acetone.

Identification

1. Melting point: 64C to 67C.

2. IR-spectrum.

3. Add dilute hydrochloric acid, filter and wash precipitate. To one of

combined filtrate and washings add potassium tetraiodomercurate solution. A pale-

brown precipitate is formed. To another part add potassium permanganate solution –

the colour of the latter is discharges immediately.

4. Dissolve the substance in acetone and dilute with water. Add dilute nitric

acid and silver nitrate solution. No opalescence is produced immediately. Heat the

solution on a water-bath - an opalescence develops:

Non-Pharmacopoeial reaction: for the substance the solution of K2Cr2O7 in

H2SO4 is added. The test-tube is covered with the paper impregnated with sodium

nitroprusside solution with 1 drop of piperidine and heated; the blue spot appears.

(CH2)3 COOHHNO3

(CH2)3 COOHO2N[H]

ROH

N

HOCH2CH2

HOCH2CH2

(CH2)3 COORSOCl2

H2N (CH2)3 COORHO (CH2)2 Cl

N

ClCH2CH2

ClCH2CH2

(CH2)3 COOH

H2ON

ClCH2CH2

ClCH2CH2

(CH2)3 COOR

-phenylbutiric acid p-nitrophenylbutiric acid

monochlorethanol

ester of p-di-(-oxyethyl) of aminophenylbutiric acid

chlorambucil

COOH

COOH

N CH2CH2CH2

CH2Cl CH2

CH2Cl CH2

2AgNO3 2H2O

N CH2CH2CH2

CH2 CH2

CH2 CH2HO

HO

2AgCl 2HNO3++

+ +

142

Assay

1. The substance is dissolved in acetone neutralised by phenolphthalein

and titrated with NaOH (indicator is- phenolphthalein). S=1.

2. The substance is heated with the excess of AgNO3 (with a reflux

condenser). The excess of AgNO3 is titrated with NH4CNS (Volhard method).

S=1/2.Carry out a blank titration.

Usage Cytotoxic (cytostatic).

Storage In well-closed containers, protected from light.

For the analysis of di-(β-chlorethyl)-amine derivatives optical methods are

used. Sarcolysin and chlorambucil can be identified and quantified by UV-

spectrophotometry.

Photometry of these substances is carried out by coloured product of their

reaction with diethylamide β-pyridine carboxylic acid. For sarcolysin extraction

photometry sodium eosinate is used; cyclophosphamide is detected as complex with

Fe(CNS)3.

IR-spectrophotometry is used for identification and quantification of these

substances.

COOH

COONa

+ NaOHN CH2CH2CH2

CH2 CH2

CH2 CH2

N CH2CH2CH2

CH2

CH2 CH2

CH2

+ H2O

Cl

Cl

Cl

Cl

143

Chapter 13. MEDICINAL SUBSTANCES DERIVATIVES OF

CYCLOALKANES AND TERPENOIDS

Plan

1. Medicinal substances derivatives of cycloalkanes.

а) general characteristic.

b) cyclopropane, amantadine hydrochloride, remantadine hydrochloride,

gludantanum. Preparation, identification, assay, usage and storage.

2. General characteristic of terpenoids.

а) medicinal substances derivatives of monocyclic terpenoids (menthol,

validolum, terpinum hydratum).

b) medicinal substances derivatives of bicycle terpenoids (camphor, camphora

monobromata, acid sulphocamphoric).

Among the various cycloalkanes cyclopropane and adamantane derivatives are

used in medicinal practice.

Cyclopropane (Cyclopropanum)

Preparation In industry it is obtained from allyl chloride:

Properties Colourless, combustible gas with the characteristic odour and

irritant taste. Boiling point –34.5C, in forms flammable mixtures with air, oxygen

and nitrogen protoxide.

Amantadine hydrochloride (Midantanum)

Tricyclo[3.3.1.13,7

]decan-1-amine

Preparation

Properties A white or almost white, crystalline powder, freely soluble in water

and in alcohol, practically insoluble in ether. It sublimes being heated.

H2C CH2

CH2

ClCH2 CH CH2

HBrClCH2 CH2 CH2 Br

Zn

NH2 . HCl

NH2 . HClBr NH2

Br2, 100 -150º

-HBr -HBr

NH3 HCl

144

Identification

1. IR-spectrum.

2. Add pyridine and acetic anhydride, heat to boiling, pour the hot solution into

dilute hydrochloric acid, cool and filter. The obtained precipitate melts at 147C to

151C.

3. Add hydrochloric acid and the solution of sodium nitrate – a white

precipitate is formed.

4. Reaction of chlorides.

Non-Pharmacopoeial reactions:

a) on boiling with NaOH educes NH3, which is detected with the red litmus

paper (blue colour);

b) the base of substance 1-aminoadamantane-forms yellow precipitate with 2-

nitroindandione-1,3.

Assay

1. Dissolve the substance in a mixture of hydrochloric acid and alcohol. Carry

out a potentiometric titration, using 0.1 M sodium hydroxide. Read the volume added

between the two pints of inflexion.

. HCl

HCl NaOH NaCl H2O+ +

+ NaOH

NH2

+ NaCl + H2O

NH2

2. Non-aqueous titration in the presence of (CH3COO)2Hg. Indicator - crystal

violet:

Usage Antiparkinsonic.

Storage In well-closed containers, protected from light, in dry place.

+ 2CH3COOH + HgCl2ClO4-

+N

H

H

H

+ 2HClO4 + Hg(CH3COO)22 NH2 . HCl

2

NH2

.HCl (CH3CO)2O+

C6H5N

NH C CH3

O+ CH3COOH + C6H5N HCl.

145

Remantadine hydrochloride (Remantadinum)

-methyl-1-adamantylmethylamine hydrochloride

Preparation Reductive amination of adamantyl ketone with formamide:

Properties White crystalline powder, odourless, with the bitter taste. Slightly

soluble in water, soluble in alcohol.

Identification

1. Solution of the substance by action of sodium nitroprusside in the presence

of acetone and sodium carbonate gets violet.

2. Reaction of Cl-.

Assay Non-aqueous titration (see amantadine hydrochloride).

Usage Remantadine has antiviral activity. It is used for treatment and

prevention of influenza.

Storage In well-closed containers, protected from light, in dry place.

Gludantanum

Glucuronide l-aminoadamantane

Properties White or slightly yellowish crystalline powder, odourless. Slightly

soluble in water.

Identification

1. Reaction of glucuronide – with cupri-tartaric solution (Fehling’s reagent).

2. Reaction with sodium nitroprusside – a green colouring develops.

Assay Non-aqueous titration.

Usage Antiparkinsonic.

Storage In well-closed containers, protected from light.

CH CH3

NH2

. HCl

CH CH3

NH2

. HClHCl

CH CH3

NH C

O

H

C

O

NH2

H

C

O

CH3

NHO

COOH

HH

H

H

OH

OH

OH

146

Medicinal substances derivatives of terpenoids Terpenoids are hydrocarbons and their oxy-derivatives (alcohols, aldehydes,

ketones, etc.); essential oils and resins of coniferwood contain such class of

substances.

In the base of terpenoids is molecule of isoprene:

Medicinal substances of monocyclic terpenoids

Levomеnthol (Mentholum) CH

3

OH

CHCH

3CH

3

**

*

(1R,2S,5R)-5-methyl-2-(1-methylethyl)cyclohexanol

The molecule of levomenthol contains 3 asymmetric carbon atoms, so there are

23=8 optically active isomers and 4 racemates.

Levomenthol occurs in the essential oil of Mentha piperita (or other species) in

free condition and as ester of acetic acid.

Preparation

1. Partial freezing - for essential volatile oil with contents of menthol up to

80% after fractional distillation. The fraction, boiling at 208-212C, is cooled till -

20C and crystals of levomenthol develop.

2. Essential oil with contents of levomenthol about 50-60% is heated with boric

acid under low pressure.

OH O

B3+

+ H3BO3+ 3H2O

3

The educed ester of boric acid has a high boiling point - it is allows to separate

it form the other parts of oil. Then by distillation with water steam after

saponification levomenthol is educed.

The synthetic menthol is obtained by two methods:

1. Reduction of thymol under the pressure and in the presence of catalyst:

H2C C CH CH2

CH3

147

OH OH

[H]

2. Industrial method of synthesis of menthol - interaction of m-cresol with

isopropyl chloride: CH

3

OH OH OH

Cl CHCH

3

CH3

[H]

Properties Prismatic or acicular, colourless, shiny crystals, practically

insoluble in water, very soluble in alcohol, in ether and in light petroleum, freely

soluble in fatty oils and in liquid paraffin, very slightly soluble in glycerol. It melts

about 43C.

Identification

1. Optical rotation from -48 to -51C.

2. Thin-layer chromatography (detector - anisaldehyde).

3. Gas-chromatography.

4. The substance interacts with dinitrobenzoyl chloride in the medium of

anhydrous pyridine and heated on the water-bath for 10 min. The obtained precipitate

is crystallised from acetone, melting point of crystals is 154-157C:

OH

CO

ClNO

2

NO2

C6H

5N

O2N

NO2

O COC

6H

5N HCl+ +

The non-Pharmacopoeial reaction - by action of 1% solution of vanillin in

conc. H2SO4, the yellow colouring developed gets red after adding of water:

OH

CO

H

OCH3

O

OH

CH

CH3

[H ]+

-H2O ++-H2

+H2O

products of polymerisation

148

Assay

Pharmacopoeia does not require quantification for levomenthol.

Non-Pharmacopoeial - method of acetylation.

The substance is acetylated with acetic anhydride in the medium of anhydrous

pyridine (heat using the reflux condenser).

The excess of acetic anhydride is decomposed with water to acetic acid, which

is titrated with NaOH solution (indicator-phenolphthalein).

Carry out a blank titration.

(CH3CO)2O + H2O 2CH3COOH

CH3COOH + NaOH CH3COONa + H2O

Usage Decongestant. External antiseptic for neuralgia, myalgia, etc. For

internal usage as sedative and vasodilatative medicine.

Storage In well-closed containers in cool place.

Validolum

25–30% menthol solution in menthyl ester of isovalerianic acid.

Preparation Reaction of esterification (levomenthol with isovalerianic acid).

Properties Transparent oily liquid with the odour of levomenthol.

Identification 1. Reaction of levomenthol - with 1% vanillin solution and conc. H2SO4.

2. Density 0.894 – 0.907 g/сm3.

Assay Alkalimetry. The contents of menthyl ester of isovalerianic acid is

detected after saponification with alcoholic КОН solution; the excess of KOH is

titrated with HCl (indicator- phenolphthalein). Carry out a blank titration. S=1.

CH3

OH

CH3H3C

+

CH3

CH3H3C

O C CH2 C H

CH3

CH3O

OH

+ (CH3CO)2O O

O C CH3

+ CH3COOH

K O H + H C l

+ K O O C C H 2 C H

C H 3

C H 3 O H

t º + K O H O C C H 2 C H

C H 3

C H 3 O

K C l + H 2 O

excess

149

Usage Sedative, reflective vasodilator.

Storage In cool place, in well-closed containers.

Terpine hydrate (Terpinum hydratum)

n-menthanediol-1,8 hydrate

Preparation By hydration of pinene. Turpentine is mixed with sawdust and

then 25% H2SO4 is added. This mixture is left in cool place for 10 – 14 days. Terpine

hydrate is in the precipitate.

Properties Colourless transparent crystals or white crystalline powder,

odourless, with a weak taste, slightly soluble in water, soluble in ethanol. Sublimates

on heating at temperature about 100C with forming crystals.

Identification

1. Add conc. H2SO4 into a hot solution of substance - the liquid gets turbid, the

odour of terpineol appears:

2. Evaporate substance with alcoholic FeCl3 solution - red, violet and green

colouring develop in different places; add benzene - a blue colouring appears.

3. Melting point 115–117C.

Assay The quantification can be carried out by colorimetry method (it is based

on the reductive properties of the substance relatively phosphorwolframic acid).

Pills of terpine hydrate can be detected by gravimetric method.

OHH3C

OHCH3H3C

. H2O

. H 2 O

O H

O H C H 3 H 3 C

H 3 C

H 2 O

O H

O H C H 3 H 3 C

H 3 C

- H 2 S O 4

2 H 2 O

O S O 3 H H 3 C

O S O 3 H H 3 C

C H 3

H S O 3 O H C

O S O 3 H H 3 C

H S O 3 O H

C H 3

C

O H 2 S O 4

O H

H 2 S O 4

e x c . c о n c .

O H

O H

150

Usage Expectorant.

Storage In well-stoppered bottles.

Medicinal substances of bicyclic terpenoids

Camphor racemic (Camphora) CH

3

O

CCH

3CH

3

Such plants as camphor tree, some species of absinthe, rosemary and sage

contain camphor.

For medical purposes use d-camphor (obtained from camphor tree -

Cinnamomum camphora); l-camphor (obtained from fir tree oil) and racemic

camphor.

Preparation

1. Natural d-camphor is obtained by distillation with water vapour from

sawdust of camphor tree. Then camphor sublimate and press.

2. l-camphor is obtained by Vershinin’s method. The initial product – fir tree

oil. At a temperature more than 180C the fraction of fir tree oil with bornyl acetate is

separated; bornylacetate saponificate with NaOH and oxidize (with HNO3) to

camphor.

O C CH3

O

OH OH2O [O]

Bornylacetate Borneol Camphor

3. Synthetic racemic camphor is obtained by Tishchenko’s method from

pinene. The fraction of pinene is isomerised to camphene (in the presence of catalyst

TiO2) and under action of formic acid obtain bornyl ester of formic acid. Then it is

saponificated to borneol and oxidised to camphor:

O C

H

OCH

O

OH

CH2

Ti2O H2O

Pinene Camphene Bornylformiate

151

OH OH2O [O]

Borneol Camphor

Properties A white, crystalline powder or friable crystalline masses, highly

volatile even at room temperature, slightly soluble in water, very soluble in ethanol,

in ether and in light petroleum, freely soluble in fatty oils, very slightly soluble in

glycerol.

Identification

1. Optical rotation (+0,15 to -0,15).

2. Melting point (174C -180C).

3. IR- spectrum.

4. Reaction with hydroxylamine in the presence of anhydrous sodium acetate

with forming of ketoxime:

5. Non-Pharmacopoeial reactions with aldehydes:

O

OCO

H

O

OCH

O

CO

H

O

CH

+

+

Furfurol

Benzaldehyde

blue-violet colouring

red colouring

Assay There is no assay for this substance in pharmacopoeia.

For assay of camphor can be used reaction with hydroxylamine or hydrazine.

For example, oxime method: it is based on the interaction of camphor with

hydroxylamine hydrochloride. Insoluble in water oxime is detected by gravimetry or

the educed HCl titrate with NaOH (indicator-bromothymol blue). S=1.

Melting point

118 C - 121C

NH2OH+ .HCl +CH3COONa

CH3O

CH3NOH

+ CH3COOH NaCl H2O+ +

152

O N OH

+ NH2OH HCl. + HCl

HCl + NaOH NaCl + H2O

Camphor can be quantified by colorimetry (reaction with aldehydes).

Usage Counter-irritant.

Storage In well-closed containers.

Camphora monobromata (Bromcamphora)

Preparation Interaction of bromine and camphor. Reaction is carried out in the

medium of chloroform or chloral hydrate, the solvent is distilled and camphora

monobromata is re-crystallised.

Properties White crystalline powder with the specific odour and taste, very

slightly soluble in water, soluble in ethanol.

Identification

1. Heat with NaOH in the presence of Zn2+

. Br- detect by reaction with

chloramine (in the presence of chloroform):

2. Melting point =74–760С.

Assay

Boil the substance with 30% KOH solution and Zn2+

(as catalyst). The educed

KBr detect by argentometry (indirect Volhard’s method); indicator Fe(NH4)(SO4)2.

Titrate with AgNO3 till disappearance of pink colouring. S=1.

O

CH3

Br

O

+ Br2

O

Br

+ HBr

O

Br

NaOH, Zn

tº

O

+ NaBr + ZnO

SO2NNa

Cl+ 2HCl SO2NH2 + NaCl + Cl2

2NaBr + Cl2 Br2 + 2NaCl

153

Br

O

Br

OKOH, Zn

t 0+KBr+2(NH4)2SO4

KBr+AgNO3

HNO3

AgBr+KNO3

Fe(NH4)(SO4)2+3NH4SCN Fe(SCN)3+2(NH4)2SO4

Fe(SCN)3+3AgNO3 3AgNO3+Fe(NO3)3

Usage Sedative, cardiokinetic.

Storage In well-stoppered bottles, protected from light.

Acid sulphocamphoric (Acidum sulfocamphoratum)

Properties White or yellowish crystalline powder, very soluble in water and in

ethanol.

Identification

1. The presence of SO2OH-group determine after heating with the mixture of

sodium carbonate and sodium nitrate. The formed SO42-

detect with BaCl2 solution.

2. The presence of keto-group confirm with 2,4-dinitrophenyl hydrazine

solution - a yellow-orange precipitate of hydrazone forms:

3. Melting point 192С –195С, optical rotation from –20 tо –24.

Assay Alkalimetry. Indicator – phenolphthalein. S=1

Acid sulphocamphoric is the part of such solution as:

Sulfocamphocainum 10% pro injectionibus

Contents: acid sulphocamphoric 49,6 g

base of procaine 50,4 g

water for injections to 1 l

O

CH2 SO2OH

+ H2O

CH2 SO2OH

N NH NO2

O2N

NO2NHH2N

O2N

+

O

CH2 SO2OH

O

CH2 SO2OH

+ NaOH

O

CH2 SO2ONa

+ H2O

154

The obtained colourless or slightly yellowish transparent liquid has pH 4,2 –

5,8. It gives reaction for -SO2OH and keto-groups of camphor. With NaOH solution

the oily precipitate of procaine-base is educed, which gives reaction for the primary

aromatic nitrogen after extraction with chloroform.

The content of sulphocamphoric acid is determined by alkalimetry, and the

content of procaine-base is determined by nitritometry.

Usage See camphor (but due to solubility in water, sulphocamphoric acid is

quickly absorbed).

155

Chapter 14. ANALYSIS OF MEDICINAL SUBSTANCES DERIVATIVES

OF PHENOLS

Plan

1. General characteristic of phenols.

2. Medicinal substances derivatives of phenols: phenol, thymol, resorcinol,

phenolphthalein, xeroformium. Preparation, properties, purity, assay, usage and

storage.

Phenols are derived from aromatic hydrocarbons by substituting one or more -

OH groups for hydrogen atom of the nucleus.

According to the contents of –OH groups they are divided in one-, two-, and

three-atomic:

Chemical properties of phenols are caused by the presence of –OH group

with the mobile hydrogen atom and by aromatic properties of benzol nucleus.

Acidic properties of phenols are stronger than alcohols due to interaction of

lone-pair electrons of oxygen atom in –OH group with π-electrons of phenol

aromatic nucleus.

By simple dissolving in alkali phenolates are formed:

Solutions of phenolates in water are very hydrolysed and can be neutralised

even with СО2 – that’s why carbonates of alkaline metals do not form phenolates.

In medicinal practice are used such medical substances as: phenol, thymol,

resorcinol, phenolphthalein, xeroformium, oxolinum.

Phenol

(Phenolum purum. Acidum carbolicum crystallisatum)

OH

Hydroxybenzene

Preparation Benzene interacts with conc. Н2SO4 with forming of benzene

sulphonic acid, the excess of acid with Ca(OH)2. Then Na2CO3 is added and sodium

OH

OHHO OH

OH

HO

фенол резорцин пирогаллолphenol resorcinol pyrogallol

OH

+ NaOH

ONa

+ H2O

156

salt is evaporated and melted with NaOH, the obtained phenolate is treated with

H2SO4:

Phenol is purified by distillation (fraction, which is boiling at t=178-182C). SO

2OH

SO3

SO3

SO3Na

SO3Na ONa

ONa OH

SO2OH

+H2SO4 +H2O

H2SO4+Ca(OH)2CaSO4+2H2O

2 +Ca(OH)2

2

Ca2

+

+2H2O

-

2

Ca2

+-

+Na2CO3 +CaCO32

+2NaOH +Na2SO3+H2O

2+H2SO4 2 +Na2SO4

t0

Properties Colourless or faintly pink or faintly yellowish crystals or crystalline

masses, deliquescent, soluble in water, very soluble in ethanol, in glycerol and in

methylene chloride.

Identification 1. Dissolve the substance in conc. NH4OH solution, add strong sodium

hypochlorite solution. A blue colour develops and becomes progressively more

intense (indophenol forms).

OH O O O NH

OH

OHO N

[O] NH3

quinone quinone imine

indophenol

2. Reaction with FeCl3 solution – the violet colouring develops, which

disappears after adding 2-propanol (as distinction from salicylic acid):

157

3. Reaction with bromine water – the slightly yellow precipitate is formed:

Assay

Bromatometry (back titration). Dissolve the substance in water, add bromide-

bromate and hydrochloric acid; this mixture is left for 30 min. Then KI add and titrate

with sodium thiosulphate until a faint yellow colour remains. Add starch solution

(indicator) and chloroform; continue titration till the solution becomes colourless.

Carry out a blank titration. S=1.

KBrO3 + 5KBr + 6HCl 3Br2 + 6KCl + 3H2O

Br2 + 2KI I2 + 2KBr

I2 + 2Na2S2O3 2NaI + Na2S4O6

Usage Antiseptic. The pure phenol can cause burns.

Storage In airtight containers, protected from light action.

Thymol (Thymolum)

5-methyl-2-(methylethyl)phenol

Preparation Synthesis from m-cresol:

OH

+ FeCl3

OFeCl2

+ HCl

OH

OH

BrBr

Br

+ 3HBr+ 3Br2

CH

CH3

CH3

OH

H3C

+ 3HBr

OH

BrBr

Br

OH

+ 3Br2

158

Properties Colourless crystals, very slightly soluble in water, very soluble in

alcohol and in ether, freely soluble in essential oils and in fatty oils, sparingly soluble

in glycerol. It dissolves in dilute solutions of alkali hydroxides.

Identification

The substance gives all the reactions for phenols except reaction with FeCl3.

1. Melting point – from 48 to 52C.

2. IR-spectrum.

3. The substance is heated with NaOH solution; after adding of chloroform

and heating this solution on the water-bath the violet colouring develops (see

resorcinol).

4. Dissolve the substance in conc. СН3СООН and add conc. H2SO4 and HNO3

- the bluish-green colour develops.

Assay

Bromatometry (direct titration).

The substance is dissolved in NaOH solution and diluted with water. KBr and

HCl are added; this mixture is titrated with 0,02 М KBrO3 till disappearance of pink

colour (indicator – methylene orange). S=3/2.

KBrO3 + 5KBr + 6HCl 3Br2 + 6KCl + 3H2O

Usage Antiseptic, helminthicide.

Storage In well-closed bottles, protected from light action.

OH

CH3

CHH3C CH3

+ 2Br2

CH3

BrBr

OH

CH CH3H3C

+ 2HBr

[H2], Ni

tº

CH3 C CH3

O

(CH3CO)2O

тимолизопропенил-м-крезол

м-крезол

OH

CH3

CHH3C CH3

OH

CH3

CH CH2H3C

CH3

OCOCH3OH

CH3 m-cresol

isopropenyl -m-cresol thymol

159

Resorcinol (Resorcinum)

Benzene-1,3-diol

Preparation

Properties A colourless or slightly pinkish-grey, crystalline powder or crystals,

turning red on exposure to light and air, very soluble in water and in alcohol, freely

soluble in ether.

Identification

The substance gives all the reactions for phenols.

1. Melting point 109C -112C.

2. Dissolve the substance in water, add conc. NaOH and chloroform, heat and

cool – an intense dark-red colouring appears which gets yellow on the addition of a

slight excess of HCl.

HO OH

H+

OH

OH

SO2OH

SO3H

SO3H ONa

ONa

H2SO4 H2SO4NaOH

ензолсуль окислотам- ензолдисуль окислота

резорцинbenzolsulphoacid

m-benzoldisulphoacid resorcinol

HCCl2

H

Cl

ONa

ONa

ONa

ONa

OH

OH

+

C

O

tH CCl2

[OH]-

[OH]-

,o

Chloroform

OH

C

O

[OH]-

-H2O

OH

OH

H

HO HOOH

H

H

NaO ONaNaO

C

ONa

O

ONa

,[OH]-

-H2O

[H]-H2O

OH

C

OH

OHHO HOOH

H

Red Yellow

160

3. The substance is mixed with potassium hydrogen phthalate and heated till

orange-yellow colouring. After cooling NaOH solution is added – an intense green

fluorescence develops:

Purity In the substance detect impurities by thin-layer chromatography and

pyrocatechol – with ammonium molybdate solution.

Assay

Bromatometry (back titration). Dissolve the substance in water; add potassium

bromide and potassium bromate solution, chloroform and hydrochloric acid. Add

potassium iodide solution and titrate with 0.1 M sodium thiosulphate, using starch

solution as an indicator. S=1.

KBrO3 + 5KBr + 6HCl 3Br2 + 6KCl + 3H2O

OH OH OH OH

Br

Br Br

+3Br2 +3HBr

Br2 + 2KI I2 + 2KBr

I2 + 2Na2S2O3 2NaI + Na2S4O6

Usage Antiseptic.

Storage In a well-closed containers, protected from light.

Phenolphthalein (Phenolphtaleinum)

3,3-bis(4-hydroxyphenyl)isobenzofuran-1(3H)-one

Preparation By heating phenol and phthalic anhydride in the presence of

H2SO4 (as catalyst):

C

C

O

O

HO OH

OHOH

HO

C

C

O

OH

OK

O

2+t

C OK

O

OH

OHC

O

C

O

NaOH

-H2O

COOK

NaO O

0

161

Properties A white or yellowish-white, crystalline or amorphous powder,

odourless or almost odourless, practically insoluble in water, soluble in 96% ethanol

and in ether.

Exists in two tautomeric forms, the first is coloured and the second is

colourless.

In alkaline medium phenolphthalein solution is red, because of destruction

lactone ring and forming of quinoid structure.

Identification

1. Dissolves in dilute solutions of alkali hydroxides and in hot solutions of

alkali carbonates. Forming a red solution, which is descharged by diluted acids.

OH

O

O

C

C

OH

-H2O

c. H2SO4

C

C

O

O

O

OH

H

OH

H

OH

O

O

C

C

OH

NaOH

OH

COONa

OH

C

OH

OH-

-H2O

OH

COONa

C

O

C

HO

C

HOO

COONa

H+

OH

O

C

O

OH-

-H2O

C

HO OH

O

C

O

OH C

HO OH

COONa

OH

Na OH-

-H2O

162

2. Melting point 258-263C.

Purity Fluoran is the side product of condensation (on synthesis), it is detected

by adding of sodium hydroxide - the turbid solution forms:

Assay

1. Photocolorimtery.

Dissolve the substance in 96% ethanol, evaporate; dissolve the residue in

sufficient glycine buffer pH 11.3 and measure the absorbance at the maximum at 555

nm. Calculate the content of substance using the specific absorbance value (A 1%, 1

cm = 1055 at the maximum at 555 nm).

2. Gravimetry.

The substance is iodinated in alkaline medium, after HCl action the precipitate

of tetraiodophenolphthalein forms, this precipitate is filtrated, washed, dried and its

weight is detected:

Usage It is used as indicator in alkalimetry, laxative.

Storage In well-closed containers.

Xeroformium

Sub-bismuth tribromophenolate with bismuth oxide

OH

H

C

C

O

O

O

O

C

C

O

O

-H2O

HO

H

Br

Br

Br O Bi O

OH

Br

Br

Br . Bi2O3

+ 4NaI + 6H2O

NaO

I

I C

I

I

O

COONa

+ 6NaOH + 4I2

OH

O

O

C

C

OH

163

Preparation

Properties Yellow powder with the weak specific odour, insoluble in water, in

ethanol and in ether.

Identification

Reactions of Bi3+

:

1. Bi(NO3)3 + 3KI BiI3 + 3KNO3

black

It is soluble in the excess of KI: BiI3 + KI KBiI4

dark-orange

2. 2Bi3+

+ 3S2-

Bi2S3

black

3. Shake the substance with NaOH solution and add HCl - a white precipitate

appears.

Assay Complexonometry after mineralisation of substance with the mixture of

diluted HNO3 and HClO4.

Usage Astringent and antiseptic.

Storage In containers, protected from light.

Br

Br

Br

O Bi

OH

O Br

Br

Br

. Bi2O3 + 2NaOH + 3H2O Br

Br

Br

ONa2 + 3Bi(OH)3

Br Br

Br

ONa

+ HCl

Br Br

Br

OH

+ NaCl

10%

o o

o

o

+

+ 2NaNO3 + 7HNO3

Br

Br

Br O Bi O

OH

Br

Br

Br . Bi2O3+ 3Bi(NO3)3 + 4H2O

Br

Br Br

ONa

2

+ H2ONaOH

Cl2; tº=20

NaBr

Br

Br Br

ONa

Br

Br Br

OH

OH

phenol

2,4,6-tribromphenol sodium 2,4,6-tribromphenolate

164

Oxolinum

1,2,3,4-tetraoxo-1,2,3,4-tetrahydronaphthaline dihydrate

Properties White crystalline powder. Freely soluble in water. Aqueous

solutions are unstable, in alkaline medium they get dark.

Usage For treatment of virous diseases of eyes, skin and influenza.

Storage In well-closed containers, protected from light.

O

O

O

O

. 2H2O

165

Chapter 15. MEDICINAL SUBSTANCES DERIVATIVES

OF AROMATIC AMINES

Plan

1. General characteristic of aromatic amines and search of substances

with antipyretic action.

2. Medicinal substances derivatives of aromatic amines: paracetamol,

xycaine (lidocaine), trimecaine:

а) Preparation;

b) properties;

c) identification;

d) impurities;

e) assay;

f) usage.

The simplest amine of aromatic origin is aniline. It has antipyretic action but

because of its toxicity it is not used in medicine. As antipyretic acetanilide was used,

but during long-term usage it caused poisoning.

Paracetamol (Paracetamolum)

N-(4-Hydroxyphenyl)acetamide

Preparation Phenol interacts with sodium nitrite in acidic medium. The

obtained p-nitrosophenol is reduced with hydrogen sulphide in ammonium medium

to p-aminophenol which is acetylated:

NHCOCH

3

OH

NH2

OH

OH

OH

NO

CH3COOHNaNO2

H2SO4

H2S; NH3

-H2O

NHCOCH3

OH

NHCOCH3

ацетанилидacetanilide

166

Properties A white, crystalline powder, sparingly soluble in water, freely

soluble in ethanol, very slightly soluble in chloroform and in ether and in methylene

chloride.

Identification

1. Melting point 168-172C.

2. UV-spectrum.

3. IR-spectrum.

4. Reaction with potassium dichromate in the presence of HCl. A violet colour

develops which does not change to red.

NHCOCH3

OH

NH2

OH

NH

O

NH2

OH

NH

O

NH2

[H ]

Cr2O7

-CH3COOH

+

2-

[O]

5. It gives reaction of acetyl (see Pharmacopoeia 2.3.1). Heat over a naked

flame.

Non-Pharmacopoeial reactions:

- with FeCl3 - a blue-violet colour develops: NHCOCH

3

OH

NHCOCH3

OFeCl2

+ FeCl3 +HCl

- due to phenol hydroxyl in the structure of paracetamol the reaction with

the diazotized salts is possible:

OH

NHCOCH3

N

R

N

ONa

NHCOCH3

N N R

+ Cl

+

- 2NaOH+NaCl+2H2O

- after acidic hydrolysis the substance gives reaction of primary aromatic

amino-group:

167

NHCOCH3

OH

N

OH

N

N

ONa

N

NaO

NH2

OH

OH

Cl

+

-

NaOH

H2O, t

HCl

0NaNO2

HCl

Purity -Impurity of p-aminophenol is determined with sodium nitroprusside

and anhydrous sodium carbonate. Any blue colour in the test solution is not more

intense than that in the standard.

-Impurity of chloroacetanilide is determined by thin-layer chromatography.

Assay

1. Cerimetry. Dissolve the substance in a mixture of water and of dilute

sulphuric acid. Boil under reflux condenser, cool and dilute with water. Add

hydrochloric acid and titrate the substance with 0.1 M cerium sulphate until a yellow

colour is obtained (indicator - ferroin). Carry out a blank titration. S=1/2.

OH

OH

H2SO4H2O;

NH2

+

CH3COOH

OH

NH2 NH

+ +Ce2(SO4)3 H2SO4

NHCOCH3

O

2Ce(SO4)2

-

N

N

N

N

3

Fe

2+

+Ce4+

3

Fe

3+

+Ce3+

red

yellow

blue

2. Nitritometry after hydrolysis. Indicator – starch-iodide paper. S=1.

168

NHCOCH3

OH

N

OH

N

NH2

OH-CH

3COOH

Cl

+

-H2O, t

HCl

0

NaNO2

HClKBr

The excess drop of titrant interacts with starch-iodide paper (it becomes blue):

2KIO3 + 5 NaNO2 + 2HCl I2 + 5NaNO3 +2KCl+H2O.

3. Alkalimetry after hydrolysis. Back titration with indicator phenolphthalein.

Carry out a blank titration. S=1.

OH

H2O;

NH2

CH3COOH

OH

NHCOCH3

-

CH3COOH + NaOH CH3COONa + H2O

NaOH+HCl NaCl+H2O

HCl

Usage Antipyretic, analgesic.

Storage In well-closed container, protected from light.

Lidocaine hydrochloride Lidocaine

(Lidocainum hydrochloridum) (Lidocainum)

CH3

CH3

NH-CO-CH2-N

C2

C2H5

H5

.HCl

CH3

CH3

NH-CO-CH2-N

C2

C2H5

H5

2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide

(hydrochloride)

Preparation 2,6-dimethylaniline is acetylated with chloranhydride of

chloracetic acid obtained 2,6-dimethylchloracetanilide is boiled in benzol with

diethylamine:

CH3H3C

NH2

ClCH2COCl

CH3COOHCH3H3C

NHCOCH2Cl

(C2H5)2NH

C6H6, HCl . HCl

CH3H3C

NHCOCH2 N(C2H5)2

169

Properties

Lidocaine: a white or almost white, crystalline powder, practically insoluble in

water, very soluble in alcohol and in methylene chloride, very soluble in ether.

Lidocaine hydrochloride: a white, crystalline powder, very soluble in water,

freely soluble in alcohol, practically insoluble in ether.

Identification

1. Melting point 66-70C (for lidocaine), 74-79 C (for lidocaine

hydrochloride).

2. IR-spectrum.

3. Reaction with picric acid in the presence of hydrochloric acid - the obtained

precipitate melts at about 230C.

4. Add fuming nitric acid and alcoholic potassium hydroxide solution, a green

colour is produced:

5. The solution of substance is made alkaline with dilute NaOH, the obtained

precipitate is dissolved in alcohol and then cobalt nitrate solution is add , a bluish-

green precipitate appears. CH

3

2 NH C CH2N

C2H5

C2H5

O

CH3

Co2+

; [OH]-

CH3

N

N

N

CH3

CH3

C

C

O

O

Co

N

CH3

CH2

CH2

C2H5

C2H5

C2H5

C2H5

CH3H3C

NHCOCH2 N(C2H5)2

. HClH2O , [H]

+, t o

CH3H3C

NH2

+ HOOC CH2N(C2H5)2. HCl

CH3H3C

NH2

HNO3 , to

CH3H3C

NH2

NO O+

-

KOH

NH

CH3H3C

OKNO-

+

CH3

CH3

NH-CO-CH2-N

O2N NO

2

C2

C2H5

H5

CH3

CH3

NH-CO-CH2-N

O2N NO

2

C2

C2H5

H5

.

+

OH

NO2

HCl

HCl

OH

NO2

-

.

170

6. Reaction of chlorides (for lidocaine hydrochloride).

The non-Pharmacopoeial reaction - after heating with an alkali or acids the

2,6-dimethylaniline formed gives reaction of primary aromatic amino-nitrogen.

H3C

NHCOCH2N(C2H5)2

CH3

H+

H2O H3C

NH2

CH3 H3C

N

CH3

NaNO2

HCl

N+

Cl

N

CH3

CH3

N

NaO

OH

NaOH

Assay

For lidocaine - non-aqueous titration.

Titrate with perchloric acid in the medium of anhydrous acetic acid. The

end-point is determined by potentiometry. S=1.

For lidocaine hydrochloride:

1. Akalimetry in the medium of alcohol; titrate with NaOH. The end-point

is determined by potentiometry. S=1.

2. Argentometry. S=1.

3. Nitritometry (after hydrolysis). S=1.

Usage. Anaesthetic.

Storage. In well-closed containers, protected from light.

Trimecaine hydrochloride (Trimecaini hydrochloridum)

CH3

CH3

NH-CO-CH2-N

CH3

C2

C2H5

H5

.HCl

Diethylamino-2,4,6-trimethylacetoanilide hydrochloride

Preparation Chloranhydride of chloracetic acid interacts with 2,4,6-

trimethylaniline and then with diethylamine:

CH3H3C

CH3

NH2

ClCH2COCl

CH3H3C

CH3

NHCOCH2Cl

(C2H5)2NH

HClCH3H3C

CH3

NHCOCH2N(C2H5)2

. HCl

171

Properties White crystalline powder. Soluble in water and in ethanol.

Identification

1. Reaction of Cl- .

2. After hydrolysis with HCl or NaOH 2,4,6-trimethylaniline is formed, which

gives reaction of primary aromatic amines:

Assay

1. Non-aqueous titration. S=1.

2. Argentometry. S=1.

3. Alkalimetry. S=1.

4. Nitritometry (after hydrolysis). S=1.

Usage Anaesthetic.

Storage In well-closed containers, protected from light.

HCl

NaNO2

CH3H3C

CH3

NH2

t0

+ NaOH

CH3H3C

NHCOCH2 N(C2H5)2

CH3

CH3H3C

CH3

N N+

Cl-

NaOH

OH

CH3H3C

CH3

N N

NaO

172

Chapter 16. MEDICINAL SUBSTANCES DERIVATIVES OF

AROMATIC ACIDS

Plan

1. Medicinal substances derivatives of benzoic acid: benzoic acid, sodium

benzoate – Preparation, properties, identification and assay, usage and storage.

2. Medicinal substances derivatives of salicylic acid: salicylic acid, sodium

salicylate, acetylsalicylic acid, phenyl salicylate, methyl salicylate. Preparation,

properties, identification and assay, usage and storage.

Aromatic acids – are derivatives of aromatic hydrocarbons, which contain one

or some hydrogen atoms of benzene nucleus substituted by carboxyl group:

CO

OH

The presence of carboxyl group in aromatic hydrocarbon decreases toxicity.

Benzoic acid (Ка=6,27.10-5

) is stronger than acetic acid (Ка=1,82.10-5

).

Benzoic acid (Acidum benzoicum)

CO

OH

Benzenecarboxylic acid

Benzoic acid occurs as its benzyl ester in benzoic resins.

Preparation

1. By oxidising of toluene:

CH3

COOH

Toluene

+3MnO2+3H2SO4 +3MnSO4+4H2O

2. By chlorination of toluene with further oxidising of the formed

benzenetrichloride:

CH3

C Cl

Cl

Cl

C

OH

OH

OH

COOHCl2

3H2O -H2O

Toluene Benzenetrichloride Trihydroxyphenylmethane

CH3 C

O

OH

C6H5 C

O

OH

173

3. Decarboxylation of phthalic acid:

COOH

COOH

COO

COO

COO

COOH

Phthalic acid

Ca(OH)2 Ca330

350

o

oCaCO3+

2

CaHCl

-CaCl2

Properties A white, crystalline powder or colourless crystals, odourless or with

a very slight characteristic odour, slightly soluble in water, soluble in boiling water,

freely soluble in alcohol, in ether and in fatty oils.

Identification

1. Melting point 121-124C.

2. Reaction of benzoates – with FeCl3 after neutralising with NaOH. A dull-

yellow precipitate, soluble in ether, is formed:

COONa COO

COOH

6 +2FeCl3+10H2O

3

Fe . Fe(OH)3. 7H2O +3 +6NaCl

Non-Pharmacopoeial reaction: with AgNO3 – a white precipitate forms.

Assay Alkalimetry in the alcoholic medium. Titrate with 0.1 M NaOH until the

colour changes from yellow to violet-red. Indicator – phenol red. S=1.

Usage Antimicrobial preservative.

Storage In well-closed containers.

Sodium benzoate (Natrii benzoas, Natrium benzoicum) COONa

Sodium benzenecarboxylate

Preparation Benzoic acid is dissolved in sodium carbonate solution:

COOH

+ NaOH

COONa

+ H2O

COOH

+ NaOH

COONa

+ H2O

174

Properties A white crystalline or granular powder or flakes, slightly

hydroscopic, freely soluble in water, sparingly soluble in alcohol.

Identification

1. It gives reaction of benzoates:

a) the substance moisten with H2SO4, gently warm – a white sublimate is

deposited on the inner wall of the tube;

b) to the solution of substance add HCl solution. The obtained precipitate

has a melting point of 120C to 124C.

2. Reactions of Na+.

The non-Pharmacopoeial reaction is reaction with FeCl3.

Assay

1. Non-aqueous titration. Titrate with 0.1 M HClO4 in the medium of

anhydrous acetic acid. Indicator – naphtholbenzein. S=1.

2. Acidimetry. Titrate with HCl in the presence of ether. Indicator – the

mixture of methylene orange and methylene blue. S=1.

Usage Expectorant.

Storage In a well-closed containers.

Salicylic acid (Acidum salicylicum)

OH

CO

OH

2-hydroxybenzenecarboxylic acid

Preparation

Kolbe-Schmitt’s method.

Interaction of solid sodium phenolate and CO2 (t = 125C) at high prassure:

COOH

2 + Na2CO3 2

COONa

+ H2O + CO2

COONa COOH+ +HCl NaCl

COONa COOH

+ +HClO4NaClO4

CH3COOH

175

At temperature about 250-300C (especially for potassium phenolate) para-

isomer is formed.

The hydrogen bond increases acidic properties:

During synthesis of salicylic acid can be obtained oxydiphenyl:

Salicylic acid is dissolved in sodium carbonate solution; oxydiphenyl is

extracted with ether.

Properties A white, crystalline powder or white colourless, acicular crystals,

slightly soluble in water, freely soluble in alcohol and in ether.

Identification

1. Melting point: 158 - 161C.

2. IR-spectrum.

3. Reaction with FeCl3 – a violet colour is produced that persists after the

addition of acetic acid:

OH

CO

OH

O FeCl

CO

O+ FeCl3

+2HCl

Non-Pharmacopoeial reactions:

a) heat the substance with sodium citrate. The substance is decomposed and the

smell of phenol appears:

OH

CO

OHOHt

o

+CO2

Phenol b) reaction with formaldehyde and conc. sulphuric acid – a pink colour

appears:

C

OH

O

O H

....

d

d

OH

ONa..

+ dC

O

O

d

125º

OH

COONaHCl

OH

COOH

176

OH

H

COOH

O

COOH

H

OH OH

COOH

C

H

COOH

OH

H

OH

COOH

C

H

COOH

O

+ C

H2

+H2SO4c.

-H2O

[O]

Assay

1. Alkalimetry in the medium of alcohol. Titrate with 0.1 M NaOH until a

reddish-violet colour is obtained. Indicator is phenol red solution. S=1.

2. Bromatometry – back titration. Indicator is the starch solution. S=1.

KBrO3 + 5KBr + 3H2SO4 3Br2 + 3K2SO4 + 3H2O

The excess of bromine: 2KI + Br2 I2 + 2KBr

I2 + 2Na2S2O3 2NaI + Na2S4O6

Usage Antiseptic, keratolytic.

Storage In a well-stoppered containers, protected from light.

Sodium salicylate (Natrii salicylas, Natrium salicylicum)

OH

CO

ONa

Sodium 2-hydroxybenzenecarboxylate

Preparation Interaction of salicylic acid and sodium hydrocarbonate or sodium

hydroxide:

COOH

OH

+ NaHCO3

COONa

OH

+ CO2 + H2O

+ 3HBr + CO2

Br Br

Br

OH

+ 3Br2

OH

COOH

OH OH

COOH

+ NaOH

COONa

+ H2O

177

Properties A white crystalline powder or small, colourless crystals or shiny

flakes, freely soluble in water, sparingly soluble in alcohol and practically insoluble

in ether.

Identification

1. IR-spectrum.

2. Reactions of salicylates:

a) with FeCl3;

b) add HCl into the solution of substance. The obtained precipitate has a

melting point of 156 -161C.

3. Reaction of Na+.

Assay 1. Non-aqueous titration. Titrate with HClO4 in the medium of anhydrous

acetic acid. Determining the end-point potentiometrically, s=1.

2. Acidimetry, s=1.

3. Bromatometry, s=1.

Usage Analgetic, antipyretic.

Storage In an airtight container, protected from light.

Acetylsalicylic acid (Acidum acetylsalicylicum, Aspirinum)

O C-CH3

O

CO

OH

2-(acetyloxy)benzoic acid

Preparation

1.

2.

3.

O

C

C

O

O

OH

CH3

OH

COOH

+C

O

O

C

O

CH3

CH3

H2SO4

cоnc.+ CH3COOH

+ H3PO3 + 3HCl3

O

C

C

O

O

OH

CH3

t=50+ CH3COOH + PCl33

OH

COOHanhydr.

ºC

кетен со спиртами и эфирами дает соответствующий эфир

OH

COOH

+ CH2 C O

O

C

C

O

O

OH

CH3

ketene

178

Properties A white, crystalline powder or colourless crystals, slightly soluble

in water, freely soluble in alcohol, soluble in ether.

Identification 1. IR-spectrum.

2. After alkaline hydrolysis dilute sulphuric acid is added: a crystalline

precipitate is formed (melting point is 156-161C):

3. The substance is heated with Ca(OH)2 – the filter paper impregnated with

nitrobenzaldehyde solution gets yellowish-green or bluish-green. After adding of

dilute HCl the colour becomes blue.

4. After alkaline hydrolysis the substance gives reaction of salicylates (with

FeCl3).

Non-Pharmacopoeial reactions:

COOH

OCOCH3

3NaOH

tº

COONa

ONa

+ CH3COONa + 2H2O

C O O N a

O N a

H 2 S O 4

O H

C O O H

+ N a 2 S O 4

m p = 1 5 6

о - 1 6 1

о

2

2

C

O C

O

CH3

OH+ 2Ca(OH)2

t C

O

C

O

CH3

OH

O -Ca

2++ (CH3COO)2Ca + H2O

(CH3COO)2Cat

CH3 CH3 + +CaO CO2

O

CCH3 CH3+

C

O

CO

OHH

NO2

C

O

H

NO2

CH2

H

CH3C

OH

C

ONO2

CH2

HC

N

C C

N

C

H O

O

o

o

2

179

a) after hydrolysis add alcohol and conc. H2SO4– the specific odour appears:

b) after hydrolysis add conc. H2SO4 and formaldehyde – the pink colouring

develops (reaction of salicylic acid).

Assay

1. Alkalimetry (back titration). The substance is dissolved in alcohol and after

hydrolysis with excess of NaOH is titrated with 0,5M HCl. Indicator is

phenolphthalein solution. Carry out a blank titration. S=1/2.

COOH

OCO CH3

+ 3NaOH

COONa

ONa

+ CH3COONa + 2H2O

2. Alkalimetry. The substance is dissolved in alcohol and titrated with NaOH.

Indicator is phenolphthalein solution. S=1.

3. Bromatometry after saponification (see salicylic acid).

Usage Analgetic, antipyretic.

Storage In an airtight containers.

Phenyl salicylate (Phenylii salicylas, Phenylium salicylicum) Salol

COOC6H

5

OH

Phenyl ester of salicylic acid

Salols – esters of phenols and aromatic acids.

Preparation

Melt phenol and salicylic acid and add PCl3:

CH3COOH + C2H5OHH2SO4

CH3C

O

OC2H5

+ H2O

NaOH + HCl NaCl + H2O

COONa

ONa

+ HCl

COONa

OH

+ NaCl

OCOCH3 OCOCH

3

COOH

+ NaOH

COONa

+ H2O20 o

180

The temperature is increased to 100C and then the mixture is cooled to 50-

55оС.

Properties A white crystalline powder with weak odour. Practically insoluble

in water, soluble in alcohol and in alkali solution, freely soluble in chloroform, very

soluble in ether.

Identification

1. To alcoholic solution of the substance add FeCl3 solution - a violet colouring

develops. After hydrolysis add an acid, the smell of phenol appears and the

precipitate of salicylic acid develops (melting point 158-161C).

C6H4OHCOOC6H5 + 3NaOH C6H5ONa + C6H4ONaCOONa + 2H2O

2. Reaction with formaldehyde on heating in the presence of conc. sulphuric

acid – a pink colouring develops (see salicylic acid).

Assay

1. Alkalimetry (back titration) after alkaline hydrolysis:

The excess of NaOH and of products of hydrolysis are titrated with HCl in the

presence of bromocresol purple:

NaOH + HCl NaCl + H2O

The products of hydrolysis are neutralised to sodium salicylate, which is

neutral relatively phenolphthalein and bromocresol purple.

One molecule of the substance is hydrolysed with one molecule of NaOH, S=1.

Usage For treatment of enterocolitis and colitis, cystitis, pyelitis.

Storage In well-closed containers, protected from light.

OH

COOH

+ 3

OH

+ PCl360º

3 3

OH

COC6H5

O

+ H3PO4 + 3HCl

OH

COOC6H5

+ 3NaOH

ONa

COONa

+

ONa

+ 2H2O

ONa

COONa

+ HCl

COONa

OH

+ NaCl

+ NaCl

OH

+ HCl

ONa

181

Salicylamide (Salicylamidum)

C

OH

O

NH2

Amide of salicylic acid

Preparation

Properties A white crystalline powder, odourless. By heating sublimates.

Sparingly soluble in water and chloroform, soluble in ethanol, in ether.

Identification

1. Reaction with FeCl3 -a violet-red colour is formed:

C

OH

O

NH2

C

O

OFeCl2

NH2

+FeCl3+HCl

2. Forming of dibromoderivative (white colour):

C

OH

O

NH2

C

OH

O

Br

Br NH2

+2Br2 +2HBr

3. Amide group is detected by educing NH3:

Assay

The substance is decomposed with an alkali; the NH3 educed is bonding with

H3BO3. The mixture of ammonium metaborates and tetraborates obtained is titrated

with hydrochloric acid solution. Carry out a blank.

NH3 + H3BO3 NH4BO2 + H2O

2NH3 + 4H3BO3 (NH4)2B4O7 + 5H2O

NH4BO2 + HCl + H2O NH4Cl + H3BO3

(NH4)2B4O7 + 5H2O + 2HCl 2NH4Cl + 4H3BO3

C NH2

O

OHOH

COOCH325% NH3

+ CH3OH

C NH2

O

OH

30% NaOHC

O

OH

ONa

+ NH3

182

Usage Analgetic, antipyretic.

Storage In well-closed containers, in protected from light action place.

Osalmid (Оxaphenamidum)

C

OH

O

NH OH

p-oxyphenylsalicylamide

Preparation

C

OH

O

O

NH2

OH

C

OH

O

NH OH

OH

Phenyl salicylate

+

p-aminophenol

+

Properties

A white powder, odourless. Practically insoluble in water, very soluble in

alcohol and alkali solution, sparingly soluble in ether.

Identification

1. The substance is hydrolysed:

C

OH

O

OH

NH2

OH

C

OH

O

NH OH

Salicylic acid

+

p-aminophenol

HCl

Then in alkali medium:

NH2

ONa

+

ONa

ONa

HCl

NaOH

NH

ONa

ONa

ONa

OH

OHN

O

резорцинат aиндо енол

(красновато-фиолетового цвета)indophenol

(red-violet colour) disodium resorcinate

183

Assay Determination of nitrogen by sulphuric acid digestion (Kjeldahl

method).

Usage Choleretic.

Storage In well-closed containers, protected from light.

Bismuth subgallate (Dermatolum, Bismuthum subgallicum)

Complex of bismuth and gallic acid

Preparation Dissolve bismuth nitrate in acetic acid and add water. Heat the

solution to 30–40С and add the solution of gallic acid.

Properties A yellow powder, practically insoluble in water, in alcohol. It

dissolves in mineral acids with decomposition, and in solutions of alkali hydroxides,

producing a reddish-brown liquid.

Identification 1. Mix the substance with water and add phosphoric acid. Heat to boiling, cool

and filter. Bismuth subphosphate is in precipitate. Filtrate the solution and add FeCl3

solution into filtrate - a black-blue colouring develops (reaction of gallic acid).

2. The precipitate obtained in the test (1) dissolve in nitric acid and carry

out reaction of bismuth with thiourea:

Assay

Complexometry. Heat to boiling with HNO3. Add potassium chlorate, heat to

boiling, add water and heat until the solution becomes colourless (mineralization).

Titrate with 0.1 M sodium edetate until yellow colour is obtained using xylenol

orange triturate as indicator. S=1.

Bi(NO3)3 +

HO

HO

HO

COOH + 2H2O

HO

HO

HO

COOBi

OH

OH

+ 3HNO3

HO

HO

HO

COO

_

Bi(OH)2

yellow-orange colour

Bi3+ + [Bi((NH2)2CS)3]

3+3(NH2)2CS

184

.Bi3+

Ind[ ] +

CH2

CH2CH2 N

N

CH2COONa

CH2COONa

CH2COOH

CH2COOH

CH2

N

N

CH2COO

CH2COO

CH2COO

CH2COOBi Na

-

HNO3

+ H3Ind + NaNO3

+

Usage Antiseptic, astringent.

Storage In well- closed containers, protected from light.

Bismuth subsalicylate (Bismuthi subsalicylas)

Complex of bismuth and salicylic acid

Properties A white powder, practically insoluble in water and in alcohol. It

dissolves in mineral acids with decomposition.

Identification

1. Add HCl , heat and boil for 5 min. Retain the filtrate for identification (2).

Wash the residue with dil. HCl, dissolve the residue in NaOH solution, neutralise

with dil. HCl. The solution gives reaction of salicylates (with FeCl3 - see

Pharmacopoeia 2.3.1).

2. The obtained filtrate (identification 1) gives reaction of bismuth (see bismuth

subgallate).

Assay Complexometry. Dissolve the substance in hot dilute perchloric acid

and titrate with sodium edetate until a yellow colour is obtained using xylenol orange

triturate as indicator (see bismuth subgallate). S=1.

Usage Antiseptic, astringent.

Storage In well-closed containers, protected from light.

185

Chapter 17. MEDICINAL SUBSTANCES DERIVATIVES OF

AROMATIC AMINOACIDS

Plan

1. General characteristic of p-aminobenzoic acid derivatives.

2. Medicinal substances, derivatives of p-aminobenzoic acid (benzocaine,

procaine, procainamide, tetracaine). Preparation, properties, identification, assay,

usage and storage.

3. Medicinal substances, derivatives of p-aminosalicylic acid (sodium p-

aminosalicylate, calcium benzamidosalicylate). Preparation, properties, identification,

assay, usage and storage.

4. Derivatives of o-aminobenzoic (anthranilic) acid (mefenamic acid,

mefenamate sodium).

5. Medicinal substances, derivatives of phenylacetic acid (diclofenac sodium).

As fatty aminoacids the aromatic aminoacids have acidic and basic properties

(acidic properties are more strong):

It is a part of fermentative complex, which is necessary for the growth of

bacteria. Esters of p-aminobenzoic acid have an anaesthetic activity and they are

synthetic substances, which are used instead of cocaine (the first anaesthetic), which

causes drug dependence.

Anaesthetic activity of cocaine is caused by the presence of benzoic acid in its

structure. In general the structure of anaesthetic group is:

Derivatives of p-aminobenzoic acid Benzocaine (Anaesthesinum)

NH2

COOC2H5 Ethyl 4-aminobenzoate

CH2 CH CH C

O

OCH3NH3C

CH CH2CH2C6H5

O

OC

CH

NH2

COOH

N ( C )n , Х=O, S, NH.CO ArХ

186

Preparation The initial substance is toluene:

Properties A white, crystalline powder or colourless crystals, very slightly

soluble in water, freely soluble in ethanol and in ether.

Identification

1. Melting point 89-92C.

2. IR-spectrum.

3. To the substance add solution of chromium trioxide – after heating the filter

paper impregnated with sodium nitroprusside and piperazine hydrate gets blue:

NH2

COOC2H5

+ H2O

NH2

COOH

+ C2H5OH

3C2H5OH + 4CrO3 3CH3COOH + 2Cr2O3+ 3H2O

4. Reaction of primary aromatic amines:

N

COR

N

N

COR

N

NaO

NH2

COR

OH

Cl

+

-

NaOH

NaNO2

HCl

Red-violet

benzocaine

p-nitrobenzoic acid

CH3

HNO3

H2SO4

CH3

NO2

K2Cr2O7

H2SO4

NO2

C

O

OH

C2H5OH; H2SO4

NO2

C

O

OC2H5

[H]

[Fe; CH3COOH]

NH2

COOC2H5

толуол п-нитротолуол

этиловый эфир п-нитробензойнойкислоты

toluene p-nitrotoluene

ethyl ester of

p-nitrobenzoic acid

187

Non-Pharmacopoeial reactions:

a) with aromatic aldehydes:

b) after alkaline hydrolysis ethanol is determined with iodoform test:

c) with chloramine – ether layer gets orange.

Assay

1. Nitritometry (determination of primary aromatic amino-nitrogen).

Dissolve the substance in a mixture of hydrochloric acid and water. Add

potassium bromide. Cool in an ice-water and titrate by slowly adding 0.1M NaNO2

with constant stirring. Determine the end-point electrochemically. S=1.

N

COR

N

NH2

COR

Cl

+

-NaNO2

HClKBr

2. Bromatometry. Back titration; carry out a blank. S=3/2.

KBrO3 + 5KBr + 6HCl 3Br2 + 6KCl + 3H2O

Br2 + 2KI I2 + 2KBr

I2 + 2Na2S2O3 2NaI + Na2S4O6

желто-оранжевого цветаоснование Шиффа

N

CH3

CH3

C

O

OR

N CH

-H2ON

CH3

CH3

C

O

H

+

C

O

OR

NH2

Schiff’s base

orange-yellow colour

NH2

COOC2H5

+ 2Br2

BrBr

NH2

COOC2H5

+ 2HBr

NH2

COOC2H5

NH2

COONa

+ C2H5OH

C2H5OH + 4I2+ 6KOH CHI3+ + 5H2O

NaOH, to

5KI+HCOOK

yellow

188

3. Iodchlorimetry. S=1/2.

ICl + KI I2 + KCl

I2 + 2Na2S2O3 2NaI + Na2S4O6

Usage Anaesthetic.

Storage In a well – closed containers, in protected from light action place.

Procaine hydrochloride (Novocainum)

NH2

COO-CH2-CH

2-N

C2H

5

C2H

5

. HCl

2-(diethylamino)ethyl 4-aminobenzoate hydrochloride

Preparation

1. From benzocaine with -diethylaminoethanol in the presence of sodium

alcoholate :

2. The initial product is p-nitrotoluene:

NH2

COOC2H5

+ 2ICl

NH2

COOC2H5

II

+ 2HCl

HCl

H2N COOC2H5

HO CH2 CH2 N

C2H5

C2H5

H2N COOCH2 CH2 N

C2H5

C2H5

CH2 N

C2H5

C2H5

H2N COOCH2 . HCl

анестезин

снование новокаина

benzocaine

base of procaine

-С2H5OH

189

Properties A white, crystalline powder or colourless crystals, very soluble in

water, soluble in alcohol, practically insoluble in ether.

Identification

1. Melting point 154-158C.

2. IR-spectrum.

3. Reaction with alcoholic potassium hydroxide after interaction with fuming

nitric acid. A brownish-red colour develops.

C2H

5OH

NH2

COOH

HNO3

NH2

COOH

O2N NO2 KOH

COOK

O2N N+

-

OK

NH O

новокаин

п-аминобензойнойензойной

нитробензойной кислотыкислота

п-нитро ензо наяп-нитротолуол

. HClCOOCH2 CH2 N

C2H5

C2H5

NH2

HCl

COOCH2 CH2 N

C2H5

C2H5

NH2

CH3COOH

Fe

NO2

COOCH2 CH2 N

C2H5

C2H5

HO CH2 CH2 N

C2H5

C2H5

NO2

CO

Cl

SOCl2

NO2

CO

OH

H2SO4

K2Cr2O7

NO2

CH3

p-nitrotoluene

procaine

-diethylaminoethyl ester of p-nitrobenzoic acid

chloranhydride of

p-nitrobenzoic acid p-nitrobenzoic acid

-diethylaminoethyl ester of p-aminobenzoic acid

NH2

COO-CH2-CH

2-N

C2H

5

C2H

5

H H2O, , t

H2N COOH HOCH2CH2NC2H5+ .HCl

+

. HCl

190

4. Reaction with dilute H2SO4 and KMnO4 – the colour immediately

discharged.

5. Reaction of chlorides (see Pharmacopoeia 2.3.1).

6. Reaction of primary aromatic amines (see Benzocaine 2.3.1).

Non-Pharmacopoeial reactions:

a) with conc. H2O2 and H2SO4 – the violet colouration develops.

b) with an alkali – the base of procaine appears (drops of oil):

Assay

1. Nitritometry (see Benzocaine). S=1.

2. Alkalimetry. S=1.

3. Argentometry (indicator - bromophenol blue). S=1.

Usage Anaesthetic.

Storage In a well – closed containers, in protected from light.

Procainamide (Novocainamidum)

NH2

CONH-CH2-CH

2-N

C2H

5

C2H

5

. HCl

4-amino-N-[2-(diethylamino)ethyl]benzamide hydrochloride

Preparation

NH2

COOCH2CH2 N

C2H5

C2H5

NH2

COOCH2CH2 N

C2H5

C2H5

+ NaCl + H2O

. HCl

+ NaOH

+ NaCl + H2OH2N C O CH2 CH2 NC2H5

C2H5

O

. HClH2N C O CH2 CH2 NC2H5

C2H5

O

+ NaOH

191

Properties A white or very slightly yellow, crystalline powder, hygroscopic,

very soluble in water, freely soluble in alcohol, slightly soluble in acetone, practically

insoluble in ether.

Identification

1. Melting point 166-170C.

2. UV-spectrum.

3. IR-spectrum.

4. Reaction of chlorides (see Pharmacopoeia 2.3.1).

5. Reaction of primary aromatic amines (see Benzocaine).

The non – Pharmacopoeial reaction is reaction with ammonium vanadate

( NH4VO3) and conc. H2SO4 - a red colouring develops.

Assay

1. Nitritometry (see Benzocaine). S=1.

2. Alkalimetry. S=1.

3. Argentometry (indicator - bromophenol blue). S=1.

Usage Anti-arrhythmic.

Storage In an airtight container, protected from light.

-диэтиламиноэтиламид

-диэтиламиноэтиламид

п-аминобензойной кислоты

-нит обензойной кислотып-нитробензойной кислоты

CONHCH2CH2

C2H5

C2H5

N

NH2

HCl

CONHCH2CH2

C2H5

C2H5

N

NH2

Ni

NO2

CONHCH2CH2

C2H5

C2H5

N

H2N CH2 CH2 N

C2H5

C2H5

NO2

CO

Cl

. HCl

Raney

-diethylaminoethylamide of p-aminobenzoic acid

-diethylaminoethylamide of p-nitrobenzoic acid chloranhydride of p-nitrobenzoic acid

192

Tetracaine hydrochloride (Dicainum)

COO-CH2-CH

2-NNH

CH3

CH3

H9C

4. HCl

2-(dimethylamino)ethyl 4-(butylamino)benzoate hydrochloride

This medicinal substance is more strong anaesthetic than procaine, but more

toxic.

Preparation

Properties A white, crystalline powder, slightly hygroscopic, freely soluble in

water, soluble in alcohol, practically insoluble in ether.

Identification

1. IR-spectrum.

2. To the solution of substance add ammonium thiocyanate solution. A white,

crystalline precipitate is formed, which after recrystallisation from water and drying

at 80C for two hours melts at about 131C.

3. Reaction with alcoholic KOH solution after interaction with fuming HNO3.

A violet colour develops:

H2N COOH NaOH

C4H9BrCOOHNHH9C4

SOCl2

C

O

Cl

H9C4NH + HO CH2 CH2 N

CH3

CH3

CH9C4NH OCH2 CH2

O

N

CH3

CH3

HCl

N

CH3

CH3

CH9C4NH OCH2 CH2

O. HCl

ПАБК ензо

диметиламиноэтиловый эфир п-бутиламинобензойной кислоты

п-бутиламинобензойной кислотыхлорангидрид диметиламиноэтанол

дикаин

-dimethylaminoethyl ester of p-butylaminobenzoic acid

chloranhydride of p-butylaminobenzoic acid -dimethylaminoethanol

p-butylaminobenzoic

acid PABA

tetracaine hydrochloride

COO-CH2-CH

2-NNH

CH3

CH3

H9C

4

COO-CH2-CH

2-NNH

CH3

CH3

H9C

4

+ NH4SCN

. HSCN + NH4Cl

. HCl

193

4. Reaction of chlorides (see Pharmacopoeia 2.3.1).

Non – Pharmacopoeial reactions:

-reaction of secondary aromatic amines.

After interaction with HCl a white precipitate of p-butylaminobenzoic acid

appears (it is dissolved in the excess of HCl):

After NaNO2 action the precipitate of N-nitrosocompound develops:

NHC4H9

COO(CH2)2 . HCl

+ 2NaOH + NaCl + H2O

NHC4H9

COONa

+ HO (CH2)2 N

CH3

CH3

N

CH3

CH3

NHC4H9

COOH

NaNO2

HCl

COOH

NON C4H9

+ H2O

+ NaCl

NHC4H9

COOH

+ HCl

NHC4H9

COONa

-HO-(CH2)2-N(CH3)2

NHH9C4 C O(CH2)2 N

CH3

CH3

OHNO3

HNH9C4

N

N

O

O-

O-

O

COOH

+

+

KOH

C2H5OH

c.

N

N

O -

O

C O O H

O K

O -

N H 9 C 4

+

+

194

Assay

1. Non – aqueous titration. Dissolve the substance in a mixture of acetic

anhydride and anhydrous acetic acid. Heat under a reflux condenser for 2 min and

add mercuric acetate solution. Titrate with 0.1M perchloric acid using crystal violet

solution as indicator. S=1.

2. Nitritometry. S=1. NH

R

H9C

4N

R

H9C

4NO

NaNO2

HCl

3. Alkalimetry. S=1.

4. Argentometry (indicator - bromophenol blue). S=1.

Usage Anaesthetic.

Storage In a well – closed container, protected from light.

Derivatives of p-aminosalicylic acid Salts of PASA are medicinal substances used for treatment of tuberculosis.

They are antimetabolites of PABA, which is necessary for the growth of micro-

organisms. Isomeric aminosalicylic acids and p-aminosalicylic acid are not

bacteriostatics.

Sodium p-aminosalicylate (Natrii para-aminosalicylas)

Sodium salt of p-aminosalicylic acid

Preparation Hydrate m-nitrophenol, carboxylate by Kolbe, and neutralise p-

aminosalicylic acid:

H2N

CO

ONa

OH

. 2H2O

COO-CH2-CH

2-NNH

CH3

CH3

H9C

4

COO-CH2-CH

2-NNH

CH3

CH3

H9C

4

(CH3CO)

2O

+ 2HClO4 + (CH3COO)2Hg

. HClO4+ HgCl2

+ CH3COOH2

2

CH3COOH. HCl

2

195

Properties A white crystalline powder, freely soluble in water, slightly soluble

in alcohol.

Na-PAS is decomposed at a temperature more 80оС.

Identification

1. Reaction of primary aromatic nitrogen (red colour):

N

OH

COOH

N

N

COONa

OH

N

NaO

NH2

COONa

OH

OH

Cl

+

-

NaOH

NaNO2

HCl

2. With FeCl3 - a red-violet colour appears (reaction of phenol hydroxyl).

OHNH2

CO

OH

O FeClNH2

CO

O+ FeCl3

+2HCl

3. Reactions of sodium.

4. UV-spectroscopy. Assay

1. Nitritometry (indicator- starch-iodine paper). S=1.

2. Acidimetry. S=1.

3. Bromatometry. S=3/2 (see Benzocaine).

4. Iodchlormetry. S=1/2(see Benzocaine).

Usage For treatment tuberculosis.

Storage In a well – closed containers, protected from light.

m-nitrophenol PASA PAS-sodium m-aminophenol

OH

NO2

[H]

NH2

OHCO2

NH2

OH

COOH

NaHCO3

NH2

OH

COONa

196

Calcium benzamidosalicylate (Bepascum)

COO

OHNHC

O

H5C

6 2

Ca2+

. 5H2O

Calcium p-benzoylaminosalicylate

Preparation

NH2

COONa

OH O

Cl

NHC

COONa

OH

O

OC6H

5

COO

OHNHC

O

H5C

6

C6H5-C

Sodium p-aminosalicylate p-benzoylaminosalicylate

CaCl2

2

Ca2+

. 5H2O

Properties A white powder. Practically insoluble in water, very slightly soluble

in ethanol with forming of turbid solutions.

Identification

1. Reaction of Ca2+

(after heating with dil. HCl).

2. Reaction with FeCl3.

Assay Complexonometry after mineralisation. S=1.

Usage For treatment tuberculosis.

Storage In a well – closed containers protected from light.

Derivatives of o-aminobenzoic (anthranilic) acid

Mefenamic acid Sodium mefenamate

(Acidum mefenaminicum) (Mefenaminum natrium)

2-[(2,3-dimethylphenyl)amino]benzoic Sodium 2-[(2,3-dimethylphenyl)

acid amino]benzoate

CO

NH

CH3H3C

ONa

CO

NH

CH3H3C

OH

197

Preparation

Properties A white or almost white, microcrystalline powder, practically

insoluble in water, slightly soluble in alcohol and in methylene chloride. It dissolves

in dilute solutions of alkali hydroxides. It shows polymorphism.

Sodium mefenamate – microcrystalline almost white powder, freely soluble in

water.

Identification

1. UV- spectrum.

2. IR- spectrum.

3. Greenish-yellow fluorescence (in methylene chloride at 365nm).

4. Solution of substance in H2SO4 after adding of K2Cr2O7 has an intense blue

colour turning rapidly to brownish – green.

5. Reaction of sodium (for salt).

Non-Pharmacopoeial reactions:

a) of diphenylamine with NO2-;

b) solution of mefenamic acid in chloroform has a blue fluorescence in UV-

light;

c) solution of mefenamic acid in conc. H2SO4 after heating gets yellow with

green fluorescence.

Assay

1. Alkalimetry. Dissolve substance with the aid of ultrasound in ethanol,

previously neutralised to phenol red. Titrate with 0.1 M NaOH. Indicator – phenol

red. S=1.

NaOH. H2SO4

CH3

CH3

NH2

H2SO4+

CH3

NH2

CH3

CH3

CH3

NH2

COOH

NH

CH3H3C

CH3

CH3

NH2COOH

Cl

[Cu]

HCl

Fe

CH3

NO2

CH3

+

CH3

CH3

NO2

H2SO4

HNO3

CH3

CH3

198

2. Non-aqueous titration. Solvent – dimethylformamide, titrate with sodium

hydroxide in a mixture of methanol and benzol. Indicator – thymol blue. S=1.

Sodium mefenamate is quantified by gravimetry.

Usage Anti-inflammatory, analgesic.

Because it is believed that aspirin and amino-pyrine owe their general purpose

analgesic efficacy to a combination of peripheral and central effects, a wide variety of

arylanthranilic acids were screened for antinociceptive (analgesic) activity if they

showed significant anti-inflammatory action. It has become evident that the

combination of both effects is a rarity among these compounds.

Storage In a well – closed container.

Derivatives of phenylacetic acid

Diclofenac sodium (Diclofenac-Natrium)

Sodium 2-[(2,6-dichlorophenyl)amino]phenyl]acetate

Preparation The initial product is bromobenzene:

Properties A white or slightly yellowish, crystalline powder, slightly

hygroscopic, sparingly soluble in water, freely soluble in methanol, soluble in

alcohol, slightly soluble in acetone.

Identification

1. IR-spectrum.

2. Thin-layer chromatography.

CH2 C

O

ONa

NH

Cl

Cl

NH

CH3H3C

COOH

NaOHNH

CH3H3C

COONa

+ H2O

COONa

NH

ClCl

Br +

ClCl

NH

CO

CH3

N

ClCl

ONaOH

tº

199

3. Dissolve the substance in alcohol, add a mixture of solution of potassium

ferricyanide and ferric chloride. Allow to stand for 5 mi. Add solution of

hydrochloric acid. Allow to stand, protected from light, for 15 min. A blue colour

develops and a precipitate is formed:

4Fe3+

+3[Fe(CN)6]4-Fe4[Fe(CN)6]3

4. Dissolve the substance in methanol, add water. The solution gives reaction

(b) of sodium (see Pharmacopoeia 2.3.1).

Assay

Dissolve the substance in anhydrous acetic acid. Titrate with 0.1 M perchloric

acid, determining the end-point potentiometrically. S=1.

Cl

N

Cl

H CH2

COONaCl

N

Cl

H CH2

COOH

+HClO4 +NaClO4

CH3COOH

Usage Anti-inflammatory, analgesic, antipyretic.

Storage In an airtight container, protected from light.

200

Chapter 18. AMIDATED DERIVATIVES OF AROMATIC

SULPHOACIDS

Plan

Medicinal substances of chloroderivatives amides of sulphoacids.

Medicinal substances of this group are derivatives of amide of

benzenesulphoacids:

SO2OH SO

2NH

2

Benzene sulphoacid Amid of benzene sulphoacid

According to their chemical structure they are divided in chloroderivatives of

amides of benzenesulphoacid and derivatives of alkylureides of sulphoacids.

Medicinal substances of chloroderivqatives amides of sulphoacids

Chloramine (Chloraminum )

Sodium N-chloro-4-methylbenzene-sulphonimidate trihydrate

Preparation If chloramine was obtained from benzol – it is named

“Chloramine B”, and if from toluene – “Chloramine T”.

H3CHOSO2Cl

H3C SO2ClNH3

H3C SO2NH2

NaClO

H3C SO2N

Cl

Na

Toluene Toluene sulphonylchloride Toluene sulphonamide

Chloramine

H3C S

O

ONaN Cl

R SO2N

Cl

R'

R'=Na, Cl

R=H, COOH R= CH3, Cl, NH2

R SO2NH C NHR'

O

R'= C4H9, C3H7

1 2

R = H, methyl,

carboxyl

R=Na, -Cl

R = halogen, amine, alkyl,

alkylamidoaryl

R = alkyl, cycloalkyl

201

During synthesis NaClO can educe NaOH, which changes direction of

reaction:

Properties A white or slightly yellow, crystalline powder. Freely soluble in

water, soluble in ethanol, practically insoluble in chloroform and in ether.

Identification

1. The solution of substance turns red litmus paper blue and then bleaches:

2. To the solution of substance add dilute H2O2. A white precipitate is formed

which dissolves on heating. White crystals melt at 137-140C.

3. Ignite the substance (cautiously, because of risk of deflagration). Dissolve

the residue in water – the solution gives reaction of chlorides (see Pharmacopoeia

2.3.1).

4. Ignite the substance (cautiously, because of risk of deflagration). Dissolve

the residue in water – the solution gives reaction of sodium (see Pharmacopoeia

2.3.1).

5. Ignite the substance (cautiously, because of risk of deflagration). Dissolve

the residue in water – the solution gives reaction of sulphates (see Pharmacopoeia

2.3.1).

Non-Pharmacopoeial reaction

In the presence of hydrochloric acid the free chlorine is educed:

Cl2 is determined with potassium iodide in the presence of chloroform

(chloroform layer gets violet):

SO2N

Cl

Na

+ HCl SO2NH2 + Cl2 + NaCl

Cl2 + 2KI I2 + 2KCl

H3C S

O

ONaNCl

+ H2O2 H3C SO2NH2O2

+NaCl +

H3C SO2NH2+ NaOH H3C SO2N

Na

H+ H2O

NaClO+H2O NaOH+HClO

H3C SO2NNa

ClH2O+ +H3C SO2NH2 NaClO

NaClO+H2O NaOH+HClO

HClO HCl+[O]

202

Assay

Iodometry. Dissolve substance in water, add KI and dilute H2SO4. Titrate with

sodium thiosulphate, using starch solution as indicator. S=1/2.

Usage Antiseptic, disinfectant.

Storage In an airtight container, protected from light at temperature of 8 to

15C.

Pantocidum

N-dichloro-p-carboxybenzolsulphamide

Properties A white crystalline powder with a weak smell of chlorine. Very

slightly soluble in water and in dilute acids, freely soluble in alkali solutions.

Identification

1. It turns red an alkaline methylene red solution, and then bleaches it.

2. By action of HCl it educes Cl2:

Free chlorine is detected with KI solution (see chloramine).

Assay

Iodometry, direct titration. The substance is dissolved in an alkali solution, KI

and the excess of H2SO4 are added. The I2 educed is titrated with sodium thiosulphate

using the starch solution as an indicator. S=1/4.

C SO2N

Cl

Cl

O

HO

C SO2N

Cl

Cl

O

HO

+ 2HCl C

O

HO

SO2NH2 + 2Cl2

H3C S

O

ONaN Cl

+ +2KI H2SO4 H3C SO2NH2+ NaClI2

K2SO4+ +

I2 + 2Na2S2O3 2NaI + Na2S4O6

I2 + 2Na2S2O3 2NaI + Na2S4O6

+ 2K2SO4SO2NH22HOOC+

+ 8KI + 3H2SO4SO2N

Cl

Cl

2NaOOC 4I2 + Na2SO4 + 4KCl +

203

The content of free chlorine – not less 50%.

Usage Antiseptic.

Storage In a well-stoppered bottles, protected from light, in a cool, dry place.

Medicinal substances derivatives of alkylureides of sulphoacids

Butamide (Butamidum)

Tolbutamide (Tolbutamidum)

N-(p-methylbenzolsulphonyl)-N`-butyl urea

Properties A white, crystalline powder, odourless. Practically insoluble in

water, soluble in alcohol, freely soluble in acetone and in chloroform.

Preparation

Identification

1. After alkaline hydrolysis and on heating it educes ammonium (specific

smell; red litmus paper gets blue). The smell of butylamine appears:

2. On long-term heating in the presence of 50% sulphuric acid (with a reflux

condenser) and neutralising the precipitate of p-toluene sulphamide (melting point of

135-138оС) appears.

H3C SO2 NH C NH C4H9

O

H3C SO2NH C

O

NHC4H9

H2O

H2SO4H3C SO2NH2

+ CO2 + C4H9NH2

H3CHOSO2Cl

H3C SO2ClNH3

H3C SO2NH2

NaOH

C2H5OH

SO2NH3C

Na

H

C4H9N C OSO2NH3C

Na

C

O

NH C4H9

HCl

толуол п-толуолсульфохлорид п-толуолсульфамид

п-толуолсульфамид-натрий

утилизоциана

натрий-бутамид

бутамид

H3C SO2NH C

O

NHC4H9

toluene p-toluenesulphochloride p-toluenesulphamide

sodium p-toluenesulphamide

butylisocyanate

sodium butamide

butamide

NH3

++ C4H9 NH2H3C SO2OK+ 3KOHH3C SO2NH C

O

NHC4H9

+ K2CO3

204

3. Sulphur is determined after mineralization with the mixture of potassium

carbonate and nitrate. Then the product of melting is dissolved in HCl and sulphates

are determined.

4. UV-spectrum.

Assay

Alkalimetry. Titrate with NaOH in the medium of ethanol, the indicator is

thymolphthalein solution. S=1.

Usage Hypoglycaemic.

Storage In dry, protected from light place.

Chlorpropamide (Chlorpropamidum)

1-[(4-chlorophenyl)sulphonyl]-3-propylurea

Preparation

Properties A white, crystalline powder, odourless or almost odourless.

Practically insoluble in water, freely soluble in acetone and in chloroform; soluble in

ethanol; slightly soluble in ether. It dissolves in aqueous solutions of alkali

hydroxides.

Identification

1. Melting point 126-130C.

2. Specific absorption in HCl solution.

3. IR-spectrum.

4. Heat with anhydrous sodium carbonate until a dull red colour appears for 10

min. After extraction with water the solution gives reaction of Cl-.

H3C SO2NH C

O

NHC4H9 + NaOH H3C SO2 N C NHC4H9 + H2O

Na O

SO2NH C

O

NHC3H7Cl

хлорпропамид

пропиламин

п-хлорбензолсульфонилмочевинап-хлорбензолсульфамид

SO2NH CCl

O

NH C3H7

C3H7NH2SO2NHCl COOCH3

NaOH CH3OH

H2SO4SO2NH CCl

O

NH2

H2N C NH2

O

Cl SO2NH2

N-п-хлорбензолсульфонилметилкарбаминат

p-chlorobenzolsulphamide p-chlorobenzolsulphonyl urea

N-p-chlorobenzolsulphonylmethyl carbaminate chlorpropamide

propylamine

205

Non-Pharmacopoeial:

a) on heating with NaOH educes NH3 (red litmus paper gets blue):

b) after mineralization with K2CO3 and KNO3 it gives reaction of SO42-

;

c) on long-term heating with a reflux condenser the precipitate of

p-chlorobenzolsulphamide develops (melting point 143-144оС):

Assay Alkalimetry. Dissolve substance in alcohol, previously neutralised using

phenolphthalein as indicator. Titrate with NaOH until a pink colour is obtained:

Usage Hypoglycaemic.

Storage In a well-closed containers, protected from light.

Glibenclamidum

Maninil*

Daonil*

1-[[4-[2-[(5-Chloro-2-methoxybenzoyl)amino]ethyl]phenyl]sulphonyl]-3-

cyclohexylurea.

Properties A white or almost white, crystalline powder, practically insoluble

in water, sparingly soluble in methylene chloride, slightly soluble in alcohol and in

methanol. It dissolves in dilute solutions of alkali hydroxides.

Identification

1. Melting point 169-174C.

2. UV-spectrum.

SO2NH CCl

O

NH C3H7 + NaOH Cl SO2ONa

+ C3H7NH2 + NH3 + Na2CO3

+

Cl SO2NHCONHC3H7

H2O

H2SO4Cl SO2NH2 + CO2 + C3H7NH2

SO2NH CCl

O

NH C3H7 + NaOH SO2 N C

Na O

Cl NHC3H7 + H2O

Cl

OCH3

C

O

N

H

(CH2)2 SO2NH C

O

N

H

206

3. IR-spectrum.

4. Thin-layer chromatography.

5. The solution of substance in H2SO4 is colourless and shows blue

fluorescence in UV-light. Then dissolve in chloral hydrate – the colour changes deep

yellow and then – brownish tinge develops.

Assay See chlorpropamide.

Usage Hypoglycaemic.

Storage In a well–closed containers, protected from light.

Predianum

1-(3-Azabicyclo[3,3,0]-octy-3-yl)-3-(p-tolyl-sulphonyl)-urea

Usage Hypoglycaemic.

Bucarbanum

N-(p-aminobenzolsulphonyl)-N`-butyl urea

Usage Hypoglycaemic.

H2N C

O

NHC4H

9SO2NH

H3C C

O

NH NSO2NH

207

Chapter 19. MEDICINAL SUBSTANCES DERIVATIVES OF

AMIDES OF SULPHANILIC ACID (SULPHANILAMIDES)

Plan

1. Preparation of derivatives of sulphanilic acid.

2. Properties and reactions of identification for sulphanilamides.

3. Methods of quantification for sulphanilamides.

4. The basic medicinal substances, derivatives of amides of sulphanilic acid;

specific reactions for identification, methods of quantification.

Sulphanilic acid is the source for Preparation of great number of medicinal

substances, combined according to their chemical structure and pharmacological

action into the group of sulphanilamides with general formula:

Knowledge of remarkable effects of such compounds in combating bacterial

infections resulted by chance from experiments on the bacterial properties of dyes.

Work on azo-dyes containing a sulphonamide nucleus have been started about 1930.

Two years later a German patent was issued covering the preparation of a number of

these dyes, including prontosil:

The first experimental data on the treatment of streptococcal infections in

animals by means of prontosil were published in 1935. Simultaneously, there

appeared a series of clinical reports on the value of prontosil in streptococcal

infections. In the same year it was suggested that the action of prontosil involved a

metabolism of the compound in the body with liberation of sulphanilamide. This led

to a study of sulphanilamide (sulfanilamide) itself, and this simple compound, which

had been prepared in 1908, was shown to be effective against streptococci.

Sulfanilamide itself has been largely superseded in medicine by derivatives,

which are less toxic or are for individual purposes preferable. These derivatives are

widely used in treatment of streptococcal, pneumococcal, meningococcal,

gonococcal, and E. coli infections.

The derivatives of sulfanilamide, that have found most successful application

in medicine, have in place of hydrogen of the sulphonamido-group such substituents

as acetyl, amidino- (guanyl), or heterocyclic radical.

Sulfacetamide, a simple acetyl derivative of sulfanilamide, known also as

albucid, was introduced for use in injuries and infections of the eyes as its

sodium salt. Sulfadiazine is used for general purposes and so are its dimethyl

NN SO2NH2

NH2

H2N

RHN SO2NHR'

208

homologue, sulfadimidine (also known as sulfamethazine and sulfamezathine),

sulfamethoxypyridazine and sulfadimethoxine. These substances are more slowly

excreted, and can be given in less frequent doses. Sulfacarbamide is used for urinary

tract infections. Sulfathiazole may cause toxic symptoms, but its derivatives

succinylsulfathiazole and phthalylsulfathiazole, are of low toxicity: these substances,

as well as sulfaguanidine, have the advantage of being only slightly absorb by

intestinal mucosa, and can therefore be used in relatively large doses in the treatment

of intestine infections. Salazodine and salazodimethoxine are products of interaction

with salicylic acid; they are given in the treatment of infections of the large intestine.

Their action is based on liberation of 5-aminosalicylic acids, which have anti-

inflammatory activity.

Preparation

1. The initial substance is sulphanilic acid:

NH2

SO2OH NH

2SO

2ONa

NHCH3CO SO

2ONa NH SO

2ClCH

3CO

R-NH2

NH SO2NHRCH

3CO SO

2NHRNH

2

NaOH (CH3CO)2O

PCl5

H2SO4

HOH

Sulpanilic acid Sodium salt of sulphanilic acid

Sodium p-acetamidebenzene sulphonate p-acetamidebenzene sulphochloride

2. The most rational is the synthesis from N-carbomethoxy aniline: R-NH

2

SO2NHRNH

2

NHCOCH3

O

NHCOCH3

SO2Cl

O

NHCOCH3

SO2NHR

O

NaOH

HOSO2Cl

N-carbomethoxy aniline p-carbomethoxyaminobenzene sulphochloride

Properties and identification

The most of sulphanilamides are amphoteric compounds. Their basic properties

are caused by the presence of aromatic aminogroup; they dissolve in acids with

forming of salts.

NH2 SO

2NHRHCl .

But these salts are easy hydrolysed in water.

209

Acidic properties are caused by the presence of hydrogen in imide group,

which can be substituted by metals with forming of salts. Substances easily dissolve

in alkali and in carbonates of alkaline metals:

NH2 SO

2NNH

2 SO2NHR R

Na

+H2O

+NaOH (Na2CO3)

Ability to dissolve in alkali is caused by the influence of radical. If it has strong

basic properties – the substance is insoluble in alkali. For example, sulfaguanidine:

NH2 SO

2NH C

NH

NH2

. H2O

1. All the sulphanilamides can be halogenated, nitrated, sulphated (reactions on

aromatic nucleus):

NH2

R

NH2

R

Br Br

+2Br2 +2HBr

2. Due to their primary aromatic aminogroup, sulphanilamides can be

diazotized. (Except the substances with acetylated aromatic aminogroup, such as

phthalylsulpfathiazole – they can react after hydrolysis):

N

SO2NHR

N

SO

2NHR

NH2

N

NaO

OH

SO2NHR

N

NaNO2, HCl

+

Cl-

NaOH

3. Lignin test.

It is used for express analysis. After hydrolysis of lignin various aromatic

aldehydes are formed. They react with primary aromatic aminogroup with forming of

Schiff’s bases (orange-red colouring).

NH2

SO2NHR C

O

OHH

O

CH3

NSO2NHR CH

O

OH

CH3

+

[H ]

-H2O

+

4. All the sulphanilamides have the atom of sulphur in sulphamide group. For

determination of sulphur substance is oxidised with the concentrated nitric acid or

melted with potassium nitrate – sulphur becomes SO42-

:

210

NH2 SO

2NHR

conc. HNO3

H2SO4 + CO2 + NH4NO3 + NO + NO2 + H2O

H2SO4 + BaCl2 BaSO4 + 2HCl

5. Hydrogen of imide group causes ability to interact with the salts of heavy

metals (CuSO4, CoCl2, FeCl3) with forming of coloured complexes, soluble and

insoluble in water. With this reaction substances can be identified.

NH2 SO

2N R

Na

R

NH2 SO

2N R

Cu

NH2 SO

2N

2СuSO4

+Na2SO4

Substance dissolve in 0,1 М solution of alkali and add the solution of salt of

heavy metal. In the presence of excess of alkali hydroxides of heavy metals can be

precipitated.

6. With 1% solution of sodium nitroprusside in the presence of alkali and with

subsequent adding of acid a red or brown-red precipitate develops.

7. On heating in a dry test-tube these substances develop the melted products

with various colouring and educe various gases. It is a reaction for identification and

distinguishing of sulphanilamides.

8. UV-spectroscopy.

Methods of quantification

1. The main method for quantification of the most sulphanilamides is

determination of primary aromatic amino-nitrogen (nitritometry).

Titrate with 0.1 M sodium nitrite in the medium of dilute hydrochloric acid in

the presence of potassium bromide (as catalyst) after cooling in ice-water. Determine

end-point electrochemically or by use of prescribed indicator:

N SO2NHRN

NH2 SO

2NHR

NaNO2, HCl

KBr

+Cl

-

2. Acid-base titration.

It is based on the properties of hydrogen in imide group. Acidic forms are

titrated with an alkali in the presence of thymolphthalein as indicator:

NH2 SO

2NNH

2 SO2NHR R

Na

+H2O+NaOH

Substances with constant of dissociation 10-7

-10-8

(sulfathiazole) are dissolved

in aqueous-acetone solution or in alcohol. Substances with constant of dissociation

10-9

(phthalylsulfathiazole, salazodine) titrate only in non-aqueous solvents

(dimethylformamide), titrate with solution of alkali in benzol with methanol.

211

Sodium salts of sulphanilamides titrate with acid in alcohol-acetone medium,

indicator – methyl orange:

NH2 SO

2N NH

2 SO2NHRR

Na

+HCl +NaCl

3. Bromatometry.

It is based on halogenation of substances. Titrate with KBrO3, the excess of Br2

is determined by iodometry; indicator - starch:

KBrO3 + 5KBr + 3H2SO4 3Br2 + 3K2SO4 + 3H2O NH

2

R

NH2

R

Br Br

+2Br2 +2HBr

Br2 + 2KI I2 +2KBr

I2 + 2Na2S2O3 2NaI + Na2S4O6

4. Iodchlorimetry.

It is based on halogenation of substances with iodine monochloride solution: NH

2

R

NH2

R

I I

+2ICl +2HCl

ICl + KI I2 + KCl

I2 + 2Na2S2O3 2NaI + Na2S4O6

5. Photocolorimetry.

It is based on the reaction of azocoupling.

6. Argentometry.

Some sulphanilamides (sulfathiazole) can form salts with Ag. They are titrated

in the presence of sodium tetraborate, using potassium chromate as indicator.

NH2 SO

2NH

N

SNH

2 SO2N

N

SAg

+AgNO3 +HNO3

Usage Antibacterial medicines. Their action is based on ability to be used

instead of PABA (which is necessary for the normal growth of micro-organisms) and

so they break metabolism of microbial cell. They have bacteriostatic effect.

212

MAIN MEDICINAL SUBSTANCES

Sulfanilamide (Streptocidum)

NH2 SO

2NH

2

4-aminobenzenesulphonamide

Properties A white or yellowish-white crystals or fine powder, slightly soluble

in water, freely soluble in acetone, sparingly soluble in alcohol, practically insoluble

in methylene chloride. It dissolves in solutions of alkali hydroxides and in dilute

mineral acids.

Identification

1. Melting point: 164.5C to 166.0C.

2. IR-spectrum.

3. Thin-layer chromatography.

4. Reaction of primary aromatic amines.

Non-Pharmacopoeial reactions:

a) on heating with alkali the smell of ammonium appears:

NH2 SO

2NH

2NH

2 SO2ONa+ NaOH

to

+ NH3

b) on melting the product obtained has a blue-violet colouring; smells of

ammonium and aniline appears;

c) by action of oxidisers (H2O2 or FeCl3) a red-violet colouring appears.

Assay Determination of primary aromatic amino-nitrogen and all the methods

may be used except neutralisation.

Storage Store protected from light.

Sulfacetamide sodium (Sulfacylum-natrium)

H2N SO2 N C

ONa

CH3. H2O

Sodium N-[(4-aminophenyl)sulphonyl]acetamide

Properties A white or yellowish-white, crystalline powder, freely soluble in

water, slightly soluble in ethanol, practically insoluble in ether.

Identification

1. UV-spectrum.

2. IR-spectrum.

3. Dissolve the substance in water, add dilute acetic acid and filter. The

precipitate, washed with a small quantity of water melts at 181C to 185C.

213

4. Dissolve the precipitate obtained in the test (3) in alcohol. Add sulphuric

acid and heat. The odour of ethyl acetate is perceptible:

5. Dissolve the precipitate obtained in the test (3), with heating, in water – the

solution gives reaction of primary aromatic amines with formation of orange-red precipitate.

6. Reactions of Na+.

Non-Pharmacopoeial reactions:

a) with СuSO4 - a bluish-green precipitate appears;

b) after hydrolysis appears the smell of acetic acid:

NH2 SO

2NH

2H2N SO2 N C

ONa

CH3. H2O

to

+CH3COOH +NaCl

HCl,

Assay Determination of primary aromatic amino-nitrogen. May be applied all

the methods mentioned above.

Storage Store protected from light.

Sulfaguanidine (Sulginum)

NH2 SO

2NH C

NH

NH2

. H2O

(4-aminophenylsulphonyl)guanidine

Properties A white or almost white, fine crystalline powder, very slightly

soluble in water, slightly soluble in acetone, very slightly soluble in alcohol,

practically insoluble in methylene chloride. It dissolves in dilute solutions of mineral

acids.

Identification

1. Melting point: 189C to 193C, determined on the dried substance.

2. IR-spectrum.

3. Thin-layer chromatography.

4. Dissolve the substance in hydrochloric acid; dilute the solution with water –

the solution, without further acidification, gives the reaction of primary aromatic

amines.

5. Suspend the substance in water, add -naphthol solution and a mixture of

water and strong sodium hypochlorite solution – a red colour develops.

H2N SO2 N C

OH

CH3

, H2O to

H2N SO2 NH2+CH3COOH

CH3COOH + C2H5OH

H2SO4

H2SO4

-H2OCH3COOC2H5

,

c.

214

Non-Pharmacopoeial reactions:

a) the product obtained after melting has a violet-red colouring and a smell of

ammonium appears (distinguishing from the other sulphanilamides except

sulfacarbamide):

NH C

NHR

NH2

NH=C-NH-C=NH

NHR NHR

2 +NH3

to

b) for distinguishing from sulfacarbamide the examined substance shake with

0.1 М sodium hydroxide solution, add 2-3 drops of phenolphthalein – a red colouring

appears (the substance is insoluble in alkali);

c) on heating with alkali educes ammonium:

NH2 SO

2NH C

NH

NH2

NH2 SO

3Na+3NaOH

to

+3NH3 +Na2CO3+H2O

Assay Determination of primary aromatic amino-nitrogen and all the methods

mentioned above.

Storage Store protected from light.

Sulfacarbamide (Urosulfanum)

NH2 SO

2NH C

O

NH2

. H2O

p-aminobenzolsulphanyl urea

Properties A white crystalline powder, odourless, with a sour taste. Slightly

soluble in water, very slightly soluble in alcohol, practically insoluble in acetone, in

dilute acids and in solutions of alkali hydroxides.

Identification

1. The product after melting has a violet-red colour and a smell of ammonium

appears.

2. On heating with alkali educes ammonium:

NH2 SO

2NH C

O

NH2

NH2 SO

3Na+NaOH

to

+2NH3 +Na2CO3

3. On heating with 5% sodium nitrite solution a red colouring appears.

Assay Nitritometry and methods mentioned above.

Storage In a well-closed containers.

215

Sulfathiazole (Norsulfazolum)

NH2 SO

2NH

N

S

4-amino-N-(thiazol-2-yl)

Sulfathiazole-sodium (Norsulfazolum-natrium)

NH2 SO

2N

N

SNa

Sodium 4-amino-N-(thiazol-2-yl)

Succinylsulfathiazole (Succinylsulfathiazolum)

NH SO2NHC

O

CH2-CH

2

N

SC

O

H

4-oxo-4-[[4-(thiazol-2-ylsulphamoyl)phenyl]amino]butanoic acid

Properties

Sulfathiazole - a white or slightly yellowish, crystalline powder, practically

insoluble in water, slightly soluble in alcohol, practically insoluble in ether and in

methylene chloride. It dissolves in dilute solutions of alkali hydroxides and in dilute

mineral acids.

Sulfathiazole-sodium – a white or slightly yellowish crystals, odourless, freely

soluble in water.

Succinylsulfathiazole - a white or yellowish-white, crystalline powder, very

slightly soluble in water, slightly soluble in alcohol and in acetone, practically

insoluble in ether. It dissolves in dilute solutions of alkali hydroxides and carbonates.

Identification

1. Melting point (for sulfathiazole 200-203C; for succinylsulfathiazole after

alkaline hydrolysis 196-204C).

2. IR-spectroscopy.

3. On heating fumes are evolved which blacken lead acetate paper (for

succinylsulfathiazole).

4. Reaction with hydroquinone and sulphuric acid. After heating add toluene,

shake – the upper (toluene) layer shows an intense pink colour (for

succinylsulfathiazole).

5. Thin-layer chromatography (for sulfathiazole).

6. With CuSO4 solution – a greyish-blue or purple precipitate is formed (for

sulfathiazole).

7. Reaction of Na+.

8. Reaction of primary aromatic amines.

216

Assay Nitritometry, determining the end-point electrometrically (for

succinylsulfathiazole – after acidic hydrolysis) and methods mentioned above.

Storage Store protected from light.

Sulfaethidole (Aethazolum)

NH2 SO

2NH

NN

S C2H

5 2(p-aminobenzolsulfamide)-5-ethyl-1,3,4-thiadiazole

Sulfaethidole-sodium (Aethazolum-natrium)

NH2 SO

2N

NN

S C2H

5Na

Sodium 2(p-aminobenzolsulfamide)-5-ethyl-1,3,4-thiadiazole

Properties A white or almost white powder, odourless. Practically insoluble in

water, very slightly soluble in ether, soluble in solutions of alkali hydroxides.

Sulfaethidole-sodium – white crystalline powder. Freely soluble in water,

practically insoluble in ether.

Identification

1. With CuSO4 develops a green precipitate becomes black.

2. With СoCl3 develops a white precipitate.

3. After melting develops a brown product, and the smell of hydrogen sulphide

appears.

Assay Nitritometry and methods mentioned above.

Storage In well-stoppered bottles, protected from light.

Sulfadimidine (Sulfadimezinum)

N

N

NH2 SO

2NH

CH3

CH3

4-amino-N-(4,6-dimethylpyrimidin-2-yl)

Properties White or almost white powder or crystals, very slightly soluble in

water and in ether, soluble in acetone, slightly soluble in alcohol. It dissolves in

solutions of alkali hydroxides and in dilute mineral acids.

Identification

1. IR-spectrum.

217

2. Thin-layer chromatography.

3. On heating to about 270C the substance decomposes and a white or

yellowish-white sublimate is formed which after recrystallisation from toluene melts

at 150-154C.

4. Reaction of primary aromatic amines.

5. With CuSO4 a yellowish-green precipitate develops which quickly becomes

brown.

6. With sodium nitroprusside solution a violet colouring appears.

Assay Nitritometry and all the methods mentioned above.

Storage In a well-closed containers, protected from light.

Phthalylsulfathiazole (Phthalazolum)

NH SO2NHC

O

C

O

OH

N

S

2-[[4-(thiazol-2-ylsulphamoyl)phenyl]carbamoyl]benzoic acid

Properties A white or yellowish-white, crystalline powder, practically

insoluble in water and in ether, freely soluble in dimethylformamide, slightly

soluble in acetone and in alcohol.

Identification

1. IR-spectroscopy.

2. After boiling with dilute sodium hydroxide solution add dilute hydrochloric

acid, neutralise – the obtained crystals melt at 200 - 203C.

3. With dilute sulphuric acid and zinc powder – fumes are evolved which

produce a black stain on lead acetate paper.

4. With resorcinol and sulphuric acid after heating add dilute sodium hydroxide

solution. Dilute this brownish-red mixture with water – an intense green fluorescence

appears which disappears on acidification:

OH

OH

C

C

O

O

O

O

C

OH

CO

OH

Oconc. H2SO4

-2H2O2 +

NaOH, H2O

.H2S + (CH3COO)2Pb PbS 2CH3COOH+

218

O

C

OH OH

COONa

OH

O

C

NaO

COONa

O

-H2O

5. Reaction of primary aromatic amines (after hydrolysis).

Purity Sulfathiazole and other primary aromatic amines are detected by thin-

layer chromatography.

Assay Alkalimetry in the medium of dimethylformamide.

Titrate with sodium hydroxide until the colour becomes blue using

thymolphthalein as indicator. Carry out a blank titration. S=1/2.

NH SO2NHC

O

C

O

OH

N

SNH SO

2NC

O

C

O

ONa

N

SNa

2NaOH

HCON(CH3)2

+H2O

Storage Store protected from light.

Sulfadimethoxine (Sulfadimethoxinum)

N

N

O

O

NH2 SO

2NH

CH3

CH3

6-(p-aminobenzolsulfamide)-2,4-dimethoxypyridine

Properties A white powder, odourless.

Identification

1. With CuSO4 develops greyish-yellow amorphous precipitate.

2. Reaction of primary aromatic amines.

Assay Nitritometry and methods mentioned above.

219

Sulfalene (Sulfalenum)

NH2 SO

2NH

N

N

OH3C

2-(p-aminobenzolsulfamide)-3methoxypyrazine

Properties A white or yellowish, crystalline powder, odourless.

Identification

1. UV-spectra (in alkaline and acidic medium).

2. Reaction of primary aromatic amines.

3. Reaction with CuSO4 develops greyish-green precipitate becomes greenish-

blue.

Assay Nitritometry (calculate on dry substance).

Storage Store protected from light.

Sulfadiazine (Sulfazinum)

NH2 SO

2NH

N

N

4-amino-N-pyrimidin-2-ylbenzenesulphonamide

Properties A white or slightly yellowish, crystalline powder, odourless.

Practically insoluble in water, slightly soluble in acetone, very slightly soluble in

alcohol. It dissolves in solutions of alkali hydroxides and in dilute mineral acids.

Identification

1. IR-spectrum.

2. Thin-layer chromatography.

3. On heating at temperature about 270C the obtained sublimate after

recrystallisation melts at 123-127C.

4. Reaction of primary aromatic amines.

5. With CuSO4 solution develops yellowish-green precipitate becomes greyish-

violet.

6. With CoСl3 solution develops violet precipitate.

7. Reaction with alcoholic resorcinol solution and sulphuric acid – after heating

of substance. A red colouring appears which becomes blue or red-blue after adding of

anhydrous acetic acid and ammonia solution.

Assay Nitritometry. The end-point is stated electrometrically.

220

Sulfamethoxypyridazine (Sulfapyridazinum)

NH2 SO

2NH

NN

OCH3

4-amino-N-(6-methoxypyridazin-3-yl)benzenesulphonamide

Properties A white or slightly yellowish, crystalline powder, colouring slowly

on exposure to light, practically insoluble in water, sparingly soluble in acetone,

slightly soluble in alcohol, vary slightly soluble in methylene chloride. It dissolves in

solutions of alkali hydroxides and in dilute mineral acids.

Identification

1. IR-spectrum.

2. Thin-layer chromatography.

3. Dissolve the substance in sulphuric acid; heat gently until a crystalline

precipitate appears. Cool and add dilute sodium hydroxide solution, ether, and shake.

Separate the ether layer, dry over anhydrous sodium sulphate and filter. Evaporate the

solvent by heating in a water-bath. An oily residue is obtained which becomes

crystalline on cooling. The residue (2-amino-6-methoxypyridazine) melts at 102C to

106C:

NH2 SO

2NH

NN

OCH3

NH2 SO

3H NH

2

NN

OCH3

H2SO4, H2O

+

2-amino-6-methoxypyridazine

4. Dissolve the substance in hydrochloric acid, dilute with water. The solution,

without further acidification, gives reaction of primary aromatic amines.

Assay Carry out the assay of primary aromatic amino-nitrogen.

Usage Sulphanilamide with long-term action.

Storage Store in a well-closed containers, protected from light.

Sulfamethoxypyridazine-sodium (Sulfapyridazinum-natrium)

NH2 SO

2N

NN

OCH3

Na

. 4H2O

Sodium 4-amino-N-(6-methoxypyridazin-3-yl)benzenesulphonamide

221

Phthazinum NN

OCH3

NH SO2NHC

O

C

O

OH

6-(phthalylbenzolsulfamide)-3-methoxypyridazin

Use for treatment of colitis and enterocolitis.

Salazodine (Sаlazopyridazinum) NN

OCH3

N SO2NHNOH

HOOC 5-(n-[N-(3-methoxypyridazinyl-6)-sulfamide]-phenylazo)-salicylic acid

Bacteriostatic and anti-inflammatory action.

Salazodimethoxinum

N

N

O

O

N SO2NHNOH

HOOC

CH3

CH3

5-{n-[(2,4-dimethoxypyridazinyl-6)-sulfamide]-phenylazo}-salicylic acid

Bacteriostatic and anti-inflammatory action.

Co-trimoxazole (Bactrim, biseptol)

It is combined medicine which consists of two substances: sulfamethoxazole

and trimethopim. Sulfamethoxazole breaks biosynthesis of dihydrofolic acid and

trimethoprimum blockades reducing of dihydrofolic acid to tetrahydrofolic acid,

which is necessary for the growth of microorganisms.

Sulfamethoxazole (Sulfamethoxazolum)

NH2 SO

2NH

NO CH

3 of 4-amino-N-(5-methyl-3-isoxazolyl)benzenesulphonamide

222

Properties A white or almost white crystalline powder, practically insoluble in

water, freely soluble in acetone, sparingly soluble in alcohol, slightly soluble in ether.

It dissolves in dilute solutions of sodium hydroxide.

Identification

1. Melting point 169-172C.

2. IR-spectrum.

3. Thin-layer chromatography.

4. Reaction of primary aromatic amines.

Assay Assay of primary aromatic amines (nitritometry), determining the end-

point electrometrically.

Storage In a well-closed container, protected from light.

223

References

1. Beckett A.H., Stenlake J.B. Practical Pharmaceutical Chemistry. New

Delhi: CBS Publishers and Distributors, 2002. –Fourth edition. – P. I. – 326 p., P. II.-

602 p.

2. British Pharmacopoeia. Version 11 and Supplements, 2007. – CD.

3. David G. Watson. Pharmaceutical analysis. – New York: Churchill

Livingston, 1999. – 337 p.

4. European Pharmacopoeia. Fourth edition and Supplement, 2004.

Council of Europe, Strasbourg. –CD.

5. European Pharmacopoeia. Fifth edition and Supplement, 2006. Council

of Europe, Strasbourg. –CD.

6. John H. Block, John M. Beale, Jr. Organic, Medicinal and

Pharmaceutical chemistry. – Philadelphia: Lippincott, Williams & Wikins, 2004. –

991 p.

7. Textbook of pharmaceutical chemistry / Revised by L.M. Atherden. –

Oxford: University press, 1999. – 915 p.

8. United States Pharmacopoeia, 2007. – CD.

9. Беликов В.Г. Фармацевтическая химия . – В 2 ч. Учебное пособие. –

4-е изд., перераб. и доп. М.: МЕД пресс-информ, 2007. – 624 с.

10. Государственная фармакопея СССР. Х издание. – М.: Медицина,

1968. – 1079с.

11. Державна фармакопея України.- 1-е вид.- X.: РІРЕГ, 2001.- 556 с.

12. Державна фармакопея України. - 1-е вид. Доповнення І. - X.: РІРЕГ,

2004. - 494 с.

13. Машковский М. Д. Лекарственнме средства. - 15-е изд., перераб.,

нспр. и доп. -М.: ООО "Издательство Новая Волна", 2005. - 1200 с.

14. Фармацевтична хімія. Навчальний посібник / За загальною ред.

П.О. Безуглого. – Вінниця: НОВА КНИГА, 2006. – 552 с.