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Jomo Kenyatta University
of
Agriculture and Technology
(Kisii CBD Cumpus)
Department of Health Sciences
SCH 2108: Organic Chemistry
SCH 2107: Inorganic Chemistry
ICH 21O6: Biochemistry 1
Practical Manual
©2011 Edition
Mr. Omwoma Solomon
Mr. Alwala O. Joseck
ContentsForeword.....................................................................................................................................3
Introduction.................................................................................................................................4
Laboratory safety.....................................................................................................................4
Waste disposal.........................................................................................................................5
Comon Laboratory apparatus......................................................................................................6
PPM conversion values and serial dilutions :...........................................................................12
Writing a practical report..........................................................................................................15
Part One....................................................................................................................................17
SCH 2108 Organic Chemistry...............................................................................................17
Experiment 1:........................................................................................................................17
Learning to Recognize Functional Groups of Organic Compounds.................................17
Experiment II.........................................................................................................................26
Unsaturated aliphatic hydrocarbons, preparation and reactions of alkenes.......................26
Experiment III.......................................................................................................................29
Aliphatic hydrocarbons – alkanes, alkenes and alkynes....................................................29
Part II........................................................................................................................................30
SCH 2107: Inorganic chemistry............................................................................................30
Experiment I..........................................................................................................................30
Dilution and preparation of solutions................................................................................30
Experiment II.........................................................................................................................31
Emission of spectra of alkali earth and transition elements..............................................31
Experiment II.........................................................................................................................32
Determination of the strength of sodium thiosulphate and percentage sodium thiosulphate in hydrated using pottasium permanganate.......................................................................32
Part III.......................................................................................................................................34
ICH 2106: Biochemistry 1......................................................................................................34
Experiment 1:........................................................................................................................34
Estimation of Amino Acid by Sorenson’s Formol Titration.............................................34
Experiment II.........................................................................................................................38
General procedure for qualitative analysis of carbohydrates............................................38
Experiment 3.........................................................................................................................41
General reactions of protein (egg protein).........................................................................41
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ForewordThe department of health sciences welcomes you to the practical component of SCH 2107, SCH 2108 and ICH 2106 courses. The experiments that form part of this courses have been carefully selected by the authors not only to reinforce your knowledge and understanding of the theoretical content of this courses but also to develope skills such as observing, recording, measuring and reporting of results. Preparation of different solvent concentrations and conversion units is also included apart from the use of specialised organic chemistry apparatus set-ups.
In order to get the most out of this courses, make efforts to do the following things:
Understand the organization of this manual that is divided into three major parts as per the courses and how to use it effectively
Understand both the purpose and the principles behind each experiment Plan your time effectively before each laboratory session
How to use this practical manual
Kindly take time and read through the information contained in the general information section of this manual. You are expected to adhere to the rules and instructions given on these pages at all times while in the laboratory. Failure to comply will result in the student being excluded from the laboratory session and consectively missing the practical marks.
Each experiment has an introduction that provides you with some background information about it but the complete set of instructions is given in the procedure part. Additional information will be given during the pre-practical briefing at the start of each practical session by the course lecturer.
Each practical will have a result section. Make sure this part is duly completed and stamped before you leave the laboratory. You will be expected to write a proper report to which the result will be attached without any erasure or alterations whatsoever.
Solomon Omwoma Joseck O. Alwala
B.Ed.Sc (MA), M.Sc.(MA) H. Dip. (Kenya Poly)
3
Introduction
General information
Laboratory safety, apparatus and practice
Preceding the laboratory class
Students are expected to acquaint themselves with the experiment to be performed before coming to class. This involves reading the instructions in the manual and other reference books that are available as well as answering any theory questions associated with the practical. It is important to come up with a flow diagram before the start of the laboratory session.
Laboratory safetyBasic laboratory rules learned at A-level shall apply. Apart from that, each and every student shall be required –A MUST- to put on a white laboratory coat, simple gas musk and googles. Sandles, open shoes and/or high heeled shoes shall NOT be allowed in the laboratory. It is also recommended that students do their own hazard assessment of the experiments they are to carry out in order to know the potentially dengerous steps for extra attention. Lab coats need to be buttoned and fit properly to cover as much skin as possible.Clothing, shirt and pants, should be cotton or wool. Synthetic clothing is strongly discouraged in the laboratory. In addition, the following safety prcautions should obseved at any point.
DO NOT use water to attempt to extinguish a reactive material fire as it can actually enhance the combustion of some reactive materials, e.g. metal compounds.
Do not use combustible materials (paper towels) to clean up a spill, as these may increase the risk of igniting the reactive compound. Soda ash (powdered lime) or dry sand should be used to completely smother and cover any small spill that occurs.
A container of soda ash (powdered lime) or dry sand should be kept within arm’s length when working with a reactive material.
If anyone is exposed, or on fire, wash with copious amounts of water, except if metal compounds are involved, which can react violently with water. In the case of a metal fire, smothering the fire is a better course of action.
The recommended fire extinguisher is a standard dry powder (ABC) type. Class D extinguishers are recommended for combustible solid metal fires (e.g, sodium, LAH), but not for organolithium reagents.
Call 9-1-1 for emergency assistance and for assistance with all fires, even if extinguished.
Pyrophoric gas releases and associated fires, should be extinguished by remotely stopping the gas flow. NEVER ATTEMPT TO PUT OUT A GAS FIRE IF THE GAS IS FLOWING.
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Waste disposalA clean and safe working environment is a standard requirement for any person practicing chemistry. It is therefore expected that students be a ware of correct procedures for disposal of the different classes of laboratory wastes. Here also are some general rules that you must take note of:
Brocken glasses in the laboratory can be a source of a hazard. Such glasses are contaminated and injuries by them can result in medical complications.
Place brocken glass into the specially marked bins Drain all harmless chemicals in solution into the sink followed by plenty of running
water. However most organic solvents are toxic, carcinogenic and potential explosives. Pour organic waste and toxic inorganic waste solutions into their respective specially lebelled containers in the fume cupboard.
Solid chemicals that are not discarded properly can be very dengerous becouse they continue reacting slowly when in contact with other solids, or solvents. Discard paper and any other solid waste into the bin.
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Comon Laboratory apparatus
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PPM conversion values and serial dilutions :
How to dilute and calculate ppm concentrations and volumes, and how to convert ppm to molarity and percentage amounts.
ppm = parts per million
ppm is a term used in chemistry to denote a very, very low concentration of a solution. One gram in 1000 ml is 1000 ppm and one thousandth of a gram (0.001g) in 1000 ml is one ppm.One thousanth of a gram is one milligram and 1000 ml is one liter, so that 1 ppm = 1 mg per liter = mg/Liter.ppm is derived from the fact that the density of water is taken as 1kg/L = 1,000,000 mg/L, and 1mg/L is 1mg/1,000,000mg or one part in one million.
OBSERVE THE FOLLOWING UNITS
1 ppm = 1mg/l = 1ug /ml = 1000ug/L ppm = ug/g =ug/ml = ng/mg = pg/ug = 10 -6 ppm = mg/litres of water
1 gram pure element disolved in 1000ml = 1000 ppm
PPB = Parts per billion = ug/L = ng/g = ng/ml = pg/mg = 10 -9
Making up 1000 ppm solutions
1. From the pure metal : weigh out accurately 1.000g of metal, dissolve in 1 : 1 conc. nitric or hydrochloric acid, and make up to the mark in 1 liter volume deionised water.
2. From a salt of the metal : e.g. Make a 1000 ppm standard of Na using the salt NaCl.
FW of salt = 58.44g.At. wt. of Na = 231g Na in relation to FW of salt = 58.44 / 23 = 2.542g. Hence, weigh out 2.542g NaCl and dissolve in 1 liter volume to make a 1000 ppm Na standard.
3. From an acidic radical of the salt : e.g. Make a 1000 ppm phosphate standard using the salt KH2PO4
FW of salt = 136.09FW of radical PO4 = 951g PO4 in relation to FW of salt = 136.09 / 95 = 1.432g.
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Hence, weigh out 1.432g KH2PO4 and dissolve in 1 liter volume to make a 1000 ppm PO4 standard.
Dilution Formula = M1V1 = M2V2
req is the required value you want.
req ppm x req vol -------------------------- = no of mls for req vol stock
e.g. Make up 50 mls vol of 25 ppm from 100 ppm
25 x 50 / 100 = 12.5 mls. i.e. 12.5 mls of 100 ppm in 50 ml volume will give a 25 ppm solution
Serial dilutions
Making up 10-1 M to 10-5 M solutions from a 1M stock solution.
Pipette 10 ml of the 1M stock into a 100 ml volumetric flask and make up to the mark to give a 10-1 M soln.Now, pipette 10 ml of this 10-1 M soln. into another 100 ml flask and make up to the mark to give a 10-2 M soln.Pipette again, 10 ml of this 10-2 M soln. into yet another 100 ml flask and make up to mark to give a 10-3 M soln.Pipette a 10 ml of this 10-3 M soln. into another 100 ml flask and make up to mark to give a 10-4 M soln.And from this 10-4 M soln. pipette 10 ml into a 100 ml flask and make up to mark to give a final 10-5 M solution.
Molarity to ppm
conc. in mg/lMolarity = ------------------------ gram mol solute x 1000
Example : What is the Molarity of Ca in a 400 ppm solution of CaCO3.Solute = 1 gram mole Ca = 40 (At. Wt.) = 40g/liter = 40 x 1000 = 40,000 mg/liter = 40,000 ppm. Solution = 400ppm (given)Hence Molarity = 400 divided by 40000 = 0.01MAnd ppm is 0.01 x 40 x 1000 = 400 ppm.(cross multiply)
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The FW of an ion species is equal to its concentration in ppm at 10-3M. Fluoride has a FW of 19, hence a 10-3M concentration is equal to 19ppm, 1M is equal to 19,000 ppm and 1ppm is equal to 5.2 x 10-5M.
ppm (parts per million) to % (parts per hundred)
Example: 1 ppm = 1/1,000,000 = 0.000001 = 0.0001% 10 ppm = 10/1,000,000 = 0.00001 = 0.001% 100 ppm = 100/1,000,000 = 0.0001 = 0.01% 200 ppn = 200/1,000,000 = 0.0002 = 0.02% 5000 ppm = 5000/1,000,000 = 0.005 = 0.5% 10,000 ppm = 10000/1,000,000 = 0.01 = 1.0% 20,000 ppm = 20000/1,000,000 = 0.02 = 2.0%
(Parts per hundred) % to ppm
Example: 0.01% = 0.0001 0.0001 x 1,000,000 = 100 ppm
ppm (parts per million) to % (parts per hundred)Example:1 ppm = 1/1,000,000 = 0.000001 = 0.0001%10 ppm = 10/1,000,000 = 0.00001 = 0.001%100 ppm = 100/1,000,000 = 0.0001 = 0.01%200 ppn = 200/1,000,000 = 0.0002 = 0.02%5000 ppm = 5000/1,000,000 = 0.005 = 0.5%10,000 ppm = 10000/1,000,000 = 0.01 = 1.0%20,000 ppm = 20000/1,000,000 = 0.02 = 2.0%
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Writing a practical reportA typical practical report has the format shown below:
1. Title page Course code and name Title of the experiment Date the experiment was performed Aim of the experiment Your Admission Number
2. Background information Outline clearly and precisely the principles underlying the practicle State the specific objectives that you intent to achieve by the end of the experiment
3. Methodology List all the apparatus stating either their capacity/ weight/size/height List all the reagents used stating their amount and quality (like 5 ml of 0.5M HCl) Describe the equipment used fully (like: Hot plate stirrer Daihan Lab Tech Co.)
Procedure
Describe every single step you did in prose report form (Like: five milliliters of 0.5 M HCl were measured and placed in 10 ml graduated measuring cylinder. Then, 2 ml of 2 M NaOH was added gradually until fizzing stoped...........). DO NOT use bullets
4. Results and discussion Records of all data must be shown Method of calculation must be shown Table of results, graphs or figures Compare results with known values Discuss the significance of the data
5. Conclusion Summary of results in a statement Was the original objective achieved?
6. Refferences References must be cited properly Examples are shown below
i. Information from ajornal: Boffetta P., Jourenkova N., Gustavsson P., 1997. Cancer risk from occupational exposure to polycyclic aromatic hydrocarbons. Cancer Causes Control 8:444–472.
ii. Information from the internet: CIOMS/WHO (Council for International Organizations of Medical Sciences in collaboration with the World Health Organization), 2002. International Ethical Guidelines for Biomedical Research Involving Human Subjects Geneva 2002 available at: http://www.fhi.org/training/fr/retc/pdf_files/cioms.pdf (5/26/2011)
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iii. Information from a book: Anil, K.D. (1994). Environmental chemistry, New Age International (p) limited, 3rd Edition New Delhi, 237-247.
iv. Information from a bronchore: Okalebo, R.J., Kenneth W.G., and Poul L.W (2002). Laboratory Methods of Soil and Plant Analysis: A working Manual second edition. Sacred Africa Nairobi Kenya.
NB: All reports should be handed in one week after the experiment is carried out or else marks will be lost
Results sheet must be written in INK and stamped before you leave the lab. No erasure or alterations on the results sheet will be accepted.
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Part One
SCH 2108 Organic Chemistry
Experiment 1:
Learning to Recognize Functional Groups of Organic Compounds
Introduction
Organic chemistry is important because it is the study of life and all of the chemical reactions related to life. Several careers apply an understanding of organic chemistry, such as doctors, veterinarians, dentists, pharmacologists, chemical engineers, and chemists. Organic chemistry plays a part in the development of common household chemicals, foods, plastics, drugs, fuels... really most of the chemicals part of daily life. Hence the importance of recognising important reactions, solutions and solvents.
Diferent solvents, solutions and reagents in organic chemistry have special characteristics that distinguish them from one another. Most of these characteristics are brought about by specific groups of atoms attached to the organic compound. These specific groups of atoms within molecules are responsible for the characteristics of chemical reactions and are called functional groups. The same functional groups will undergo the same or similar chemical reactions regardless of the size of the molecule it is part of.
Some of these reactions that are functional group based include
1. Combustion reaction for alkanes
When alkanes reacts with excess of oxygen, large amount of energy is produced and the products are CO2(g) and H2O(g). This type of reactions has a wide range of applications, such as heating, cooking and use as fuel for engines.
2. Halogenations: alkanes react with the first three members of the halogen family (Br2, Cl2, F2) by replacement reaction in the presence of UV light. For example:
3. Addition reactions of alkenes Addition of hydrogen halides to alkenes. For example:
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In general, hydro halogens are symbolized as: HX (where X is a halogen atom). Halogens are added to the double bond according to Markovnikov’s rule: when HX is added to an Alkene, the hydrogen atom adds to the carbon atom of the double bond that already has the greater number of hydrogen atoms. For example:
Addition of sulfuric acid also according to Markovnikov’s rule. For example:
Addition of water to alkenes (acid-catalyzed hydration), also according to Markovnikov’s rule. For example:
Adding halogens as bromine. For example:
4. Hydrogenation in the presence of a variety of catalysts (platinum, palladium or nickel). For example:
Hydrogenation is often done when liquid vegetable oil is converted to solid fats in making margarine and solid cooking fats.
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5. Polymerization reaction: This reaction takes place in the presence of certain catalysts as free radical initiators, such as HOOH or any other initiators. For example:
6. Oxidation: This term includes many reaction types. The most important are listed below.
Combustion. For example:
C2H4 (g) +3O2 (g) → 2CO2 (g) + 2H2O (g) + heat
Oxidation by oxidizing agent as KMnO4, OsO4, Na2SO3 and NaHSO3. For example:
7. Reactions involving alcohols
Alcohols are compounds that contain a hydroxyl group attached to a saturated carbon atom. The simplest alcohol is methanol CH3OH.
Alcohols have relatively high boiling points when compared to hydrocarbons with the same molecular weight. This is because alcohols are polar compounds and, what is more important, they form hydrogen bonding between their molecules. The ability to form hydrogen bonding is also the reason why alcohols are soluble in water. In particular, alcohols with 5 carbon atoms or less per one hydroxyl group in each molecule are soluble in water in all proportions.
Alcohols are neutral compounds and have acidity similar to that of water. Alcohols have three categories, primary, secondary and tertiary, as shown below:
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Primary alcohol is oxidized easily in the presence of an oxidizing agent such as K2Cr2O7/H3O+ or KMnO4/H3O+ or OH-.
The first step of oxidation is to form an aldehyde which has the general structural formula:
Where R is any alkyl group.
Oxidation of a primary alcohol does not finish with aldehydes, since aldehydes are oxidized faster than alcohol itself and produce carboxylic acids. For example:
Secondary alcohols oxidized to ketones which can not be oxidize further. For example
Ketones have the general formula:
Where R and R/ are any alkyl groups.
Ketones are neutral organic compounds. Ketones do not create hydrogen bonding between their own molecules, but can create hydrogen bonding with water and are
soluble in water, especially with 5 carbon atoms of less per group in a molecule.
8. Reactions involving carboxylic acids
Carboxylic acids have the general formula:
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The simplest one is methanoic HCOOH (formic) acid, which has this formula:
Carboxylic acids are weak acids (not completely ionized in water). For example:
Carboxylic acids have relatively high boiling points when compared with hydrocarbons which have the same molecular weight. This is because carboxylic acids are polar compounds and, what is more important, they form hydrogen bonding between their molecules. The ability to form hydrogen bonding is also the reason why carboxylic acids are soluble in water especially when there are 5 or less carbon atoms
per one group, in each molecule.
Materials:
Acetic acid CH3COOH solution
Ethanol C2H5OH
Acetone CH3COCH3
Cyclohexane C6H12
Cyclohexene C6H10
Bromine solution
Water
KMnO4 solution
1M HCl solution
Equipments:
Safety glasses
Glass stir rod
20 test tubes + 5 stoppers
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pH paper
Black paper
Experimental procedure
In this experiment you will study the properties of hydrocarbons and other known organic compounds. You will learn how to recognize the functional groups of those compounds.
a. Study the properties of carboxylic acid, ethanol, and acetone.
1. Add 2 ml of CH3COOH, C2H5OH and CH3COCH3 to 3 separate test tubes.
2. Cut a 2-cm piece of pH paper and put it on a tray. Add one drop from each of the solutions to the pH paper using the glass rod. Use new pH paper for each test tube. Write your results in table 1. Indicate which of the compounds is acidic and which is neutral.
________________________________________________________________________
3. Add 3 ml of water to each of the test tubes, and cork it with a stopper. Shake it gently and carefully remove the stopper. Watch to see if CH3COOH, C2H5OH and CH3COCH3 are soluble in water and write it in table 1. Describe your observations.
________________________________________________________________________
4. Add 2 ml of CH3COOH, C2H5OH and CH3COCH3 to 3 separate test tubes. Add to each test tube 3 ml of cyclohexane. Cork it with a stopper, shake it gently, and carefully remove the stopper. Watch to see if CH3COOH, C2H5OH, and CH3COCH3 are soluble in cyclohexane and write it in Table 1. Describe your observations:
________________________________________________________________________
Solubility in Cyclohexane
Solubility in water
pHSolution
CH3COOH
C2H5OH
CH3COCH3
Table 1
b. Study the properties of cyclohexane and cyclohexene
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This part should be conducted in a hood.
1. Add 2 ml of C6H12 and C6H10 to two separate test tubes.
2. Cut a 2-cm piece of pH paper and put it on a try. Add one drop from each of the solutions to the pH paper using the glass rod. Use new pH paper for each test tube. Write your results in table 2. Are the solutions acidic or neutral?
_______________________________________________________________
3. Add 3 ml of water to each of the test tubes, and cork it with a stopper. Shake it gently and carefully remove the stopper. Watch to see if C6H12 and C6H10 are soluble in water and sum up your observations in Table 2. Describe your observations.
________________________________________________________________________
4. Add 2 ml of C6H12 and C6H10 to two separate test tubes. Add to each test tube 3 ml of cyclohexane. Cork it with a stopper, shake it gently and carefully remove the stopper. Watch to see if C6H12 and C6H10 are soluble in cyclohexane and write it in Table 2.
Describe your observations.
________________________________________________________________________
c. Reaction with Br2 to distinguish between alkanes and alkenes.
This part should be conducted in a hood.
1. Add about 3 ml of solutions C6H12 and C6H10 to two separate test tubes.
2. Add to each of the test tubes about 10 drops of bromine solution. Cork the test tubes immediately and place them in a light area. Describe your observations:
________________________________________________________________________
3. To two additional test tubes add about 3 ml of solutions C6H12 and C6H10. Then add to each of the test tubes about 10 drops of bromine solution.
4. Wrap each of the test tubes with black paper and place them in a dark area for a few minutes.
5. After a few minutes remove the black paper and compare the color of the solutions in the two test tubes. Write your results in Table 2. Describe your observations.
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Reactivity with Br2
Solubility in Cyclohexane
Solubility in water
pHSolution
C6H12
C6H10
Table 2
d. Oxidation using an acidic solution of KMnO4(aq)
1. Add about 5 ml of CH3COOH, C2H5OH and CH3COCH3 to three separate test tubes.
2. To each of the test tubes add about 2 drops of KMnO4 solution and 2 drops of HCl solution. Notice the change in color in each of the test tubes and write down your observations:
________________________________________________________________________
e. Summarize your observations of previous steps in table 3:
Reactivity with KMnO4
Reactivity with Br2
Solubility in Cyclohexane
Solubility in water
pHSolution
CH3COOH
C2H5OH
CH3COCH3
C6H12
C6H10
Table 3
II – Identification of Unknown Materials
You will receive from you technician an unknown solution – one of which you have studied in the previous section. You will need to discover the unknown solution.
1. Plan an experiment by which you can discover the unknown solution.
________________________________________________________________________
2. Receive your technicians approval for your plan.
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3. Conduct the experiment you planned in a hood and identify your unknown solution.
4. Summarize Experimental procedure and your results.
________________________________________________________________________
5. The unknown solution is: ______________________________
Experiment II
Unsaturated aliphatic hydrocarbons, preparation and reactions of alkenes
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Although industrially the major source of simple alkenes is the cracking of petroleum, in the laboratory, alkenes can be prepared by dehydration of an alcohol under acidic reaction conditions. The reaction proceeds via an Elimination Reaction. Elimination reactions occur when a saturated reactant becomes an unsaturated product:
X Y
R CH CH2 R CH = CH2 + X-Y
In this reaction, a hydrogen atom and OH- are eliminated, but carbon atoms are not. The carbon atoms in the product are bonded to fewer atoms than in the reactant. Thus the driving force for many elimination reactions is the loss of a small, stable molecule, such as H 2O, which increases the entropy (disorder) of the system.
Concentrated sulfuric acid or phosphoric acid are used as dehydrating agents.
Procedure
Set upthe distillation apparatus as shown below
Using a small glass funnel, transfer 8 ml of cyclohexane as completely as possible into a 50 ml round bottomed flask. Add 2 ml of concentrated phosphoric acid and two boiling chips. Heat the flask gently over a gauze until slow distilaation commences at a reaction temperature of a bout 115 oC. The cyclohexene formed should take about 30 min and should be stooped if the temperature rises above 130oC.
Wash the flask, still-head, condensor and receiver adoptor immediately and dry them in the oven. Transfer the distillate to a 100 ml separating funnel and add 10 ml of a 0.5 M solution of NaHCO3. Stopper the funnel and shake gently, opening the tap at intervals to allow the
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carbondioxide that is produced to escape. When the rate of gas evolution has slowed down, shake more vigorously. Allow the two layers to separate, remove the stopper and run the lower (aqueous) layer into a conical flask.
Pour the upper layer into a second 100 ml conical flask, add anhydrous magnesium sulfate and swirl for 10 min. Filter the clear, dry product through a small glass funnel into a clean dry weighed 100 ml conical flask.
Weigh the product, label with the name of the product and its boiling point range.
Calculate the percentage yield of the product obtained using the following calculation:
Write the balanced chemical equation for the synthesis eg
ROH + R’COOH R’COOR + H2O
Then identify the minority reactant i.e. this example requires equal number of moles of alcohol and acid. Suppose that in your calculations, from the masses of each used and their molecular weights (MW), show that there are fewer moles of alcohol than of acid, then the alcohol is the minority reactant. Thus we base our yield on this reactant (ROH)
Moles of ROH = Mass (ROH)/MW(ROH)
Moles of product = Mass(R’COOR)/MW(R’COOR)
Percentage yield = (Moles of product/moles of ROH) x 100
Carry out the following tests and write equations for the reaction taking place
i. To 1 ml of cyclohexene formed, add a solution of bromine in tetrachloromethaneii. To 1 ml portion of dilute potassium permanganate (0.3%) in a test tube, add about five
drops of cyclohexene. Shake the tube well for 1-3 min and note the results.iii. To a 2 ml portion of cold concentrated sulfuric acid in a test tube, add about 10 drops
of cyclohexene. Shake the tube well and note the results. Discard the contents by pouring them into a beaker containing at least 50 ml of water.
Hand in the remaining product to the technician at the end of the laboratory period
Learning outcome:
By the end of the experiment, the student should be able to set up a typical organic reaction apparatus and purify an organic product using separation techniques. The importance of using simple organic reactions to identify the product should be understood. The student should now be familiar with an elimination reaction and also be able to caculate the percentage yield of product obtained.
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Questions
Draw the product formed from the following reactions:
CH3(CH2)CH=CH-CH3 + KmnO4
Write an equation for an elimination reaction between 2-bromopropane and hot potassium ethoxide, CH3-CH2-OK (KBr and ethanol are also products)
Experiment III
Aliphatic hydrocarbons – alkanes, alkenes and alkynes.Introduction
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Hydrocarbons, the simplest type of organic compound, are a large group of substances containing only H and C atoms. Some common fuels, such as natural gas and gasoline, are hydrocarbon mixtures. Hydrocarbons such as ethylene, acetylene and benzene are are important precusor reactants used to make other compounds.
Hydrocarbons are divided into two broad classes: aliphatic hydrocarbons and aromatic hydrocarbons. There are three types of aliphatic hydrocarbons: alkanes, alkenes and alkynes.alkanes (also known as paraffins) are hydrocarbons that contain only single bonds. Their general formula is CnH2n+1. These compounds comprise a homologous series, one in which each member differs from the next by a –CH2- (methylene) group. Each C in alkanes is bonded to the maximum number of other atoms (C or H) and are thus, referred to as saturated hydrocarbons. A hydrocarbon that contains at least one C=C bond is called an alkene. With two hydrogen atoms removed to make the double bond, alkenes have the general formula, CnH2n. Because their carbon atoms bond fewer than the maximum of four atoms each, alkenes are considered unsaturated hydrocarborns. Hydrocarbons that contain at least one C≡C bond are called alkynes. Their general formula is CnH2n-2. Becaouse their carbon atoms bond fewer than the maximum of four atoms each, alkenes are considered unsaturated hydrocarbons.
Hydrocarbons that contain at least one C≡C bond are called alkynes. Their general formula is CnH2n-2 becaouse they have two H atoms fewer than alkenes of the same length.
Aromatic hydrocarbons are planar molecules with one or more rings of six C atoms and are often drawn with alternating single and double bonds. In this experiment, the reaction of both saturated and unsaturated hydrocarbons are explored by use of various reagents while the preparation aspect is also accounted for in the cases of alkenes and alkynes.
Procedure
Part A: reactions of Alkanes
Carry out the following tests with hexane
i. Ignite a few drops on a crucible lid and note the flame colourii. Add a few drops KMnO4 (aq)/dil H2SO4
iii. Add a few drops KMnO4 (aq)/dil Na2CO3
iv. Add a few drops of Bromine water
Place 0.5 cm3 of hexane in a test tube and add a few drops of bromine water and then stand in light. Repeat the same putting the test tube in the dark. Observe and record any changes that take place. Write an equation for the combustio of hexane.
Part B: Properties of Alkenes
Carry out the following reactions on 1-pentene or cyclohexene.
i. Ignite a few drops on a crucible lid and note the colour of the flame.
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ii. Add a few drops of KMnO4 (aq) / dil H2SO4
iii. Add a few drops of KMnO4 (aq) / dil Na2CO3
Part C: Preparation and properties of alkynes
Laboratory preparation of ethyne gas. In the lab ethyne is prepared by the action of water on calcium carbide. The chemical equation is:
The apparatus used for producing the ethyne gas is shown below.
Water is slowly dropped on small pieces of calcium carbide kept in a conical flask. Calcium carbide reacts with water to give off ethyne gas (or acetylene gas). The gas is collected by downward displacement of water as it is insoluble in water.
Physical properties of ethyne
The low molecular weighted alkynes such as ethyne, propyne and butyne are gases at room temperature. Alkynes with five to 13 carbon atoms are liquid at room temperature. Higher molecular weighted alkynes are solids at room temperature. Alkynes are insoluble in water but are soluble in organic liquids. Gaseous alkynes can produce a feeling of anesthesia when inhaled.
Chemical properties of ethyne
1. Combustion : Ethyne burns in air with a sooty flame. It forms carbon dioxide and water and gives out heat.
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HC≡CH + 5O2 4CO2 + 2H2O + heat
The sooty flame is due to higher amount of carbon in ethyne than in methane. All the carbon atoms cannot get oxidized while burning this makes the flame sooty. But if ethyne is burnt with a proper control, for example, if the gas is made to pass through a small nozzle, then it gets ample air mixture to burn completely. This type of complete combustion is used for acetylene lamps in industries. Acetylene lamps produce very luminous non-sooty flame.
Ethyne combined well with oxygen can burn to give a flame whose temperature is 3000°C. This oxy-acetylene flame is used for welding metals, where very high temperatures are required.
2. Reactivity : Alkynes are more reactive than the alkanes or alkenes due to the presence of unsaturated bonds. The pi bond is not localized and hence can be broken easily in a reaction. Such a reaction is called addition reaction. In an addition reaction, the pi bond converts into a sigma bond and the alkyne will become an alkane. For example if ethyne is reacted with chlorine, it becomes 1,1,2,2 tetra-chloro-ethane.
Similarly, addition reaction with bromine will give rise to 1,1,2,2, tetra-bromo-ethane. Bromine water decolorizes on reaction with ethyne. This is a prominent test for testing unsaturated nature of hydrocarbons.
When hydrogen is added to ethyne, and heated in the presence of nickel, it becomes ethene and then proceeds to become ethane. The bonds become saturated.
This is known as the process of hydrogenation. The addition of hydrogen to a double or triple bonded hydrocarbon leads to saturation of the bonds.
When hydrochloric acid is added to ethyne, it becomes first chloro-ethene and then 1,1, dichloro-ethane. The reaction is shown below.
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3. Polymerization : Alkynes like ethyne undergo polymerization, which is a process whereby long chain molecules are formed. Ethyne is an unsaturated gas. It polymerizes in two fashion, one way forms cyclic or aromatic hydrocarbons and another way forms long chain polymers. For making aromatic or cyclic hydrocarbons, only a few of the pi bonds are broken. For making long chain polymer, all its pi bonds can be broken and another ethyne can be attached. The second ethyne molecule’s all pi bond can be broken to add another ethyne molecule. In this way a very long chain molecule or polymer can be produced.
When ethyne (gas) is passed over a solution of copper chloride and ammonium chloride in HCl, it undergoes polymerization reaction to form solid divinylacetylene. The reaction is shown below.
When ethyne gas is passed through a red hot tube, it polymerizes to form an aromatic compound called benzene (C6H6). The reaction is shown below.
Uses of ethyne
Ethyne burns in oxygen to give a very luminous light. Hawkers use this as lamps.
Ethyne is used for oxy-acetylene flame used for industrial welding.
Ethyne is used for manufacture of synthetic plastics, synthetic rubbers, and synthetic fibers.
Ethyne is also used making many industrially useful organic compounds like acetaldehyde, acetic acid, etc.
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Part II
SCH 2107: Inorganic chemistry
Experiment I.
Dilution and preparation of solutionsAIM: The purpose of this experiment is to enable the students prepare different given concentrations of solutions for experimental work either in the field or for practical use. Dilution is a process in which more solvent is added to a solution in order to lower its concentration. It’s one of the common activity encountered when working with solutions, one whose concentration is known (stock solution) is diluted to a lower concentration.
Procedure:
You are provided with 1 M H2SO4. Using the information provided at the beginning of these manual on conversions, prepare the following concentrations
1. 0.004M H2SO4 in 50 ml
2. 0.25N H2SO4, in 50 ml
3. 0.004 moles in 25 ml.
Using the information at the beginning of these manual, prepare 1.0%(M/V) silver nitrate solution from 24ml of a 3.0%(M/V) stock solution of silver nitrate provided.
Given a salt of AgNO3, prepare 1000ppm of a nitrate stock solution.
Set up a titration experiment in which you will use 0.25N H2SO4 prepared to determine the concentration in moles of the 1.0 % (M/V) silver nitrate.
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Experiment II
Emission of spectra of alkali earth and transition elements.
Introduction
The flame test is useful confirmatory test for Na+, K+, Ca2+, Sr3+, Fe2+/Fe3+, Ba2+, Li+ etc. It depends on the fact that metallic Chlorides and other metallic compounds are volatile at high temperatures and some imparts a characteristic colour to Bunsen flame.
Procedure:
1).Strongly heat a clean Platinum / Nichrome Wire / Spatula until it gives no appreciable colour to the flame.
2). Dip it into original solutions in turn and heat in the hot region of the bunsen flame.
3). Observe and note the characteristic colours produced.
Note: Make sure that after each flame test you dip the wire or spatula in 1:1 Hydrochloric acid/water solution and heat again.
Questions:
1).Explain the origin of the colours observed in the tests above.
2). Explain why different ion’s give flames of different colours.
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Experiment II
Determination of the strength of sodium thiosulphate and percentage sodium thiosulphate in hydrated using pottasium permanganate
INTRODUCTION
OXIDATION-REDUCTION REACTION [REDOX] OR TITRATION:
Redox reactions involve ions and are brought about by transfer of electrons from the reducing agent to the oxidizing agent. Oxidation in ionic reactions means a loss of electrons and reduction gain of electrons. A simple example to illustrate the nature of redox reaction is that a sample of iron [ii] oxide is oxidized to iron [iii] oxide. The process can be represented by the equation:-
2FeCl2 + Cl2 = 2FeCl2
and from which it is apparent that the iron atom undergoes a valency changes from two to three. The effect of chlorine on iron [ii] chloride results in a similar valency change.
2FeCl2 + Cl2 = 2FeCl2
both reactions could be summarized by the following representation
Fe2+-------------------------------oxidation -----------------Fe3+
Or more fully by the balanced ionic equation.
Fe2+ + e- [e = electron]
Oxidation of a metal ion involves the raising of Oxidation State by removal of one or more electrons; and in reduction a lowering of Oxidation State by accepting one or more electrons. [Oxidizing agent an electron acceptor and reducing agent electron donor]. The strength of oxidizing agent is measured by its ability to accept electrons.
OXIDATION WITH POTASIUM PERMANGANATE:
Potassium permanganate is a valuable and powerful oxidizing agent especially in either acid or alkali. In three mineral acids only sulphuric acid is suitable for use with potassium permanganate. Dilute acids are used.
PROCEDURE:
1. Weigh about 0.35g sodium thiosulphate and transfer into 250ml volumetric flask
2. Dissolve in distilled water and make upto mark with distilled water
3. Pipette triplicates of 25ml of 0.05N KmnO4 into conical flasks.
4. Add 10ml of 0.1N KI solution and 10ml of 2N H2SO4
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5. Add a few drops of starch solution
6. Titrate with sodium thiosulphate solution run from a burette until the colour changes from dark green to colourless.
CALCULATIONS
1. Record ml. NaS2O3
2. Calculate Normality of Na2S2O3
3. Calculate % NaS2O3 in the hydrate
4. Calculate grams per litre of Na2S2O3
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Part III
ICH 2106: Biochemistry 1
Experiment 1:
Estimation of Amino Acid by Sorenson’s Formol Titration
AIM: To estimate the amount of amino acid present in the whole of the given solution.
PRINCIPLE:
The acid group present in the glycine can be titrated with NaOH. It is not easy in this case because the amino group present will interfere at the end point. To prevent it excess of formaldehyde is used by which the amino group is blocked by the formation of methylene glycine. Then it is titrated with NaOH using phenolphthalein indicator.
REAGENTS REQUIRED:
(i) Standard oxalic acid 0.1 N
(ii) Link solution NaOH
(iii) Formaldehyde
(iv) Phenolphthalein indicator
(v) Amino acid solution
PROCEDURE:
Standardisation of NaOH Rinse a clean burette first with distilled water and then with the link solution of NaOH. Rinse a clean 20ml pipette first with distilled water and then with the given standard oxalic acid. Pipette out 20ml of oxalic acid into a clean conical flask. Add a few drops of phenolphthalein indicator and titrate against NaOH taken in the burette. The end point is the appearance of permanent pale pink colour. Repeat the titration for concordant values. Estimation of Amino acid Make up the given amino acid solution with distilled water to 100ml in a volumetric flask, observing the usual precautions. Shake the solution well for uniform concentration. Pipette out 20ml of amino acid solution into a clean conical flask. Add 5 ml of HCHO and keep it for 2 minutes. Then titrate it against the NaOH solution taken in the burette. Phenolphthalein is used as the indicator. The end point is the appearance of permanent pale pink colour. Repeat the titration for concordant values. Blank titration Pipette
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out 20ml of distilled water in a clean conical flask. Add 5ml of HCHO and keep it aside for a few minutes. Add 1-2 drops of phenolphthalein indicator. Titrate it against the NaOH solution taken in the burette. The end point is the appearance of permanent pale pink colour. Repeat the titration for concordant values.
Result:
The amount of amino acid present in the whole of the given solution = _______ g
EXPT 1
Titration I
Standardisation of NaOH
Concentration of Oxalic acid = 0.1 N
Calculation
Volume of oxalic acid, V1 = ml
Normality of oxalic acid, N1 = N
Volume of NaOH, V2 = ml
Normality of NaOH, N2 = N
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Titration II
Estimation of amino acid
Calculation
Volume of NaOH, (Test value) = ml
Volume of NaOH, (Blank value) = ml
Volume of NaOH used to titrate amino acid = Test value – Blank value
= ml
Titration III
Blank titration
Calculation
Volume of amino acid, V1 = ml
Normality of amino acid, N1 = N
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Volume of NaOH, V2 = ml
Normality of NaOH, N2 = N
Strength of amino acid = V(NaOH) x N(NaOH) = V(amino acid) x N(amino acid)
Amount of amino acid present in 100ml of the given solution
= Equivalent weight x Normality x 100/1000
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Experiment II
General procedure for qualitative analysis of carbohydrates
PREPARATION OF REAGENTSMolisch’s reagent
5% a naphthal in alcohol, i.e., 5g of anaphthal dissolved in 100ml of ethanol.Iodine solution
0.005% in 3% KI, i.e., 3g of KI dissolved in 100ml water and then 5mg ofiodine is dissolved.
Benedict’s solution17.3g of sodium citrate and 10g of sodium carbonate are dissolved in 75ml ofwater. 1.73g of CuSO4.5H2O is dissolved in 20ml of water. Mix the CuSO4solution with alkaline citrate with constant stirring, finally the whole volume ismade up to 100ml with water.
Barfoed’s reagent13.3g of copper acetate in 200ml of water and add 2ml of glacial acetic acid.
Bial’s reagentDissolve 300mg of orcinol in 100ml of concentrated HCl.
Seliwanoff’s reagentDissolve 50g of resorcinol in 100ml of con.HCl in the ratio of 1:2.
Concentrated HClConcentrated H 2SO4Osazone Reagent
Phenyl hydrazine hydrochlorideSodium acetateAcetic acid
PRINCIPLE OF REACTIONSMolisch’s test
Con. H2SO4 dehydrates carbohydrates to form furfural and its derivatives. This product combines with sulphonated a naphthal to give purple colour.
Iodine testIodine forms a coloured absorption complex with polysaccharides due to theformation of micellae aggregate. Iodine will form a polysaccharide inclusioncomplex.
Benedict’s testCarbohydrates with a potential aldehyde or ketone group have reducingproperty when placed in an alkaline solution. Cupric ions present in thesolution will be reduced to cuprous ion. This will give a red colouredprecipitate. Moreover, this test is more specific for reducing sugars.
Barfoed’ testBarfoed’s reagent is weakly acidic and it is only reduced by monosaccharides. Prolonged boiling may hydrolyze the disaccharide to give false positive test.
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Bial’s testWhen pentose is heated with con.HCl, furfural, which condenses with orcinolin the prescence of ferric ion to give a blue green colour.
Seliwanoff’s test Ketoses are dehydrated more rapidly than aldose to give a furfural derivatives,which then condenses with resorcinol to form a red colour complex.
Mucic acid testMonosaccharides are converted into respective dicarboxylic acid in the presence of strong oxidizing agent con HNO3. Galactaric acid will form a colourless broken glass piece shaped crystals.
Osazone testCompounds containing aldehyde and keto groups form crystalline osazone with phenyl hydrazine hydrochloride. Osazone crystals have characteristic shape and melting point which helps in the identification of reducing sugar.
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Procedure
The technician shall give you a number of unknown solutions which you shall carry out the tests outlined above and make atable similar to the one shown above
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Experiment 3
General reactions of protein (egg protein)
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Procedure
The technician shall provide you with different solutions of which you will carry out the tests above and make inferences.
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