HYDROXY COMPOUNDS (ALCOHOLS)Click me for intro!

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INTRODUCTION Alkane

with hydroxyl group (OH) General formula for aliphatic alcohol, CnH2n+1OH Aromatic

alcohol phenol (-OH attached to the benzene rings)

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INTRODUCTIONOH CH3CH2-OH CH2-OH

ALIPHATIC ALCOHOL (OH group attached directly to the alkyl group)

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INTRODUCTIONOH OH OH CH3

Br

AROMATIC ALCOHOL (OH group attached directly to the aryl group)

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CLASSIFICATION Methyl

alcohol CH3-OH R-CH2-OH

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Alcohols Alcohols Alcohols

20

30

R R-CH-OH R R-C-OH R5

NOMENCLATUREStructure CH3-OH CH3CH2-OHCH3CH(OH)CH3

General name

IUPAC name

methyl alcohol ethyl alcohol isopropyl alcohol cyclohexyl alcohol

methanol ethanol 2-propanol cyclohexanol

OH

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Naming the alcohol1. The suffix e in the alkane parent name is replaced by ol 2. The location of the OH on the longest chain is given by the smallest possible number

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IUPAC rules for naming alcohols1. Determine parent name 2. Give the lowest number to the carbon bearing the OH group 3. Identify substituent groups and their position 4. Name the alcohol

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Naming Alcohols, R-O-H:CH3 CH3CHCH2CHCH3 OH 4-methyl-2-pentanol CH3 CH3CCH2CH2CH3 OH 2-methyl-2-pentanol

2oCH3 HO-CHCH2CH3 sec-butyl alcohol 2-butanol

3oCH3CH2CH2-OH n-propyl alcohol 1-propanol

2o

1o

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Naming Alcohols

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For phenol, C attach to the OH group is C 1OH

OH

OH

CH3

CH2CH3 3-ethylphenol

Br 3-bromophenol 2-methylphenol

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Alcohol with 2 hydroxy groupsStructureCH2(OH)CH2-OHCH3CH(OH)CH2-OH HO-CH2CH2CH2-OH OH-CH2CHCH2-OH OH

General nameethylene glycol propylene glycol trimethylene glycol glycerol

IUPAC name1,2-ethanediol 1,2-propanediol 1,3-propanediol 1,2,3-propanetriol

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Benzene derivatives with 2 OH groups are name as benzenediol

OH

OH

OH

OH

OH1,4-benzenediol (hydroquinone)

OH1,3-benzenediol (resorcinol) 1,2-benzenediol (catechol)

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EXCERCISE 1. Name the following compounds using IUPAC nomenclature (a) -CH2CH(CH3)CH2-OH

(b)

-OH NO2

(b)

-OH Br14

PHYSICAL PROPERTIES Most

simple alcohols are liquids MeOH & EtOH are volatile liquids, b.p. 65oC & 78oC respectively M , b.p. r ROH

with C > 12 are solids

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PHYSICAL PROPERTIES No.

of OH , b.p. b.p. ROH > alkane & RX because of Hbonding b.p. ROH straight chain > ROH branch b.p. 1o ROH > 2o ROH > 3o ROH

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PHYSICAL PROPERTIES(ii) Boiling point As molecular weight increase, van der Waals forces increase, boiling point will increase too. For isomeric alcohol (same molecular formula) increase in boiling point with increasing carbon number. decrease in boiling point with branching. boiling point in descending order:1 alcohol > 2 alcohol > 3 alcohol17

PHYSICAL PROPERTIES (Solubility)Alcohols and water have the ability to form inter-molecular H-bonding Methanol, ethanol & propanol are completely soluble in water Solubility decreases with relative Mr because of the bigger hydrophobic area Solubility increases with the no. of -OH groups18

PHYSICAL PROPERTIES (Solubility)+ -

H

R H R H

O O-

H+

+

Hydrogen bonding

Hydrophilic area

-

H

R

OH

O O-

H

Hydrophobic area

+

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PHYSICAL PROPERTIES (Solubility)Phenol is not completely soluble in water below 66oC, but completely soluble above this temp. Phenol is a colourless crystalline solid which is hygroscopic 4-nitrophenol is more soluble in water than 2nitrophenol because can form H-bonding with water molecules

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PHYSICAL PROPERTIES (Solubility)2-nitrophenol + 4-nitrophenol

H- O

O

-

O + O N

-

+

H

O

-

H

+

N O O + - H O+

Intramolecular H-bonding

H

H

Intermolecular H-bonding21

Acidity of phenol & alcoholphenol > water > alcohol Ethanol, very weak acid & only can react with strong base such as Na or K to produce a conjugate base (ethoxide ion) CH3CH2-OH CH3CH2-O- + H+

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Acidity of phenol & alcohol CH CH O-

is e- richer than OH-, thus H2O 3 2 > acidic than CH3CH2OH

Phenol

> acidic than H2O & CH3CH2OH because phenoxide ion formed is more stable The phenoxide ion formed is stabilised by resonance effect23

Acidity of phenol & alcohol

O

Hrelease proton

O + H+Phenoxide ion

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Phenoxide ion stabilityO O25

O

O

O -

-

Example:OH CH2CH2-OH CH2-OH OH

acidity increase

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Example:COOH OH

>Na2CO3 NaHCO3 Weak bases KOH

> CH CH -OH3 2

ACIDITY DECREASE

K, Na NaH Very strong bases27

NaOH Strong bases

EXCERCISE 1. Arrange the following compounds in the order of increasing boiling point. Explain your answer. 1,2-ethanediol , n-butane , 1-propanol , 1,3-propanediol 2. Predict which of the compound is more soluble in water. Briefly explain your answer. (a) propane & 1-propanol (b) 1-propanol & 1,2-propanediol (c) 2-propanol & 2-pentanol28

PREPARATION OF ALCOHOLS1. Fermentation of carbohydrate

-fermentation of sugars by yeast to form ethanol C6H12O6 2CH3CH2OH + 2CO2

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PREPARATION OF ALCOHOLS2.Hydration of Alkenes follows Markovnikovs rule Example:CH3CH=CH2 H2O / H2SO4 CH3CH-CH3 OH

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PREPARATION OF ALCOHOLSMechanismCH3CH=CH2 + H+ CH3CH-CH3 2o carbonium+ OH

CH3CH-CH3 OH

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PREPARATION OF ALCOHOLS3. Hydrolysis of HaloalkanesRX + OH- (aq) ROH + X-

CH2Cl + NaOH(aq)

CH2OH

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PREPARATION OF ALCOHOLS4. Addition of Grignard reagent to

carbonyl compounds

10, 20 & 30 alcohols can be prepared by addition of Grignard reagent with carbonyl compounds followed by hydrolysis

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PREPARATION OF ALCOHOLS(a) Formation of 1o alcohols (Grignard reagent + methanal)

CH3CH2-MgCl + H2C=O OMgCl methanal 1o Alcohol

CH3CH2CH2H3O+ CH3CH2CH2-OH + Mg(OH)Cl34

PREPARATION OF ALCOHOLS(b) Formation of 2o alcohols (Grignard reagent + aldehyde)CH3 CH3CH2-MgCl + HC=O ethan OMgClal

CH3 CH3CH2CHH3O+ CH32o Alcohol CH3CH2CH-OH

+ Mg(OH)Cl35

PREPARATION OF ALCOHOLS(c) Formation of 3o alcohol (Grignard reagent + ketone)O CH3-MgCl + CH3-C-CH3propanon e

O-MgCl CH3-C-CH3 CH3 H3O+ O-H3o Alcohol

CH3-C-CH3 + Mg(OH)Cl CH3

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EXCERCISE 1. Write the chemical equation for the following reaction: i. tert-butyl alcohol from an alkene ii. isopropyl alcohol from an alkyl halide 2. Draw the structure of A, B and C: i. CH3 O CH3-C-MgCl + ii. CH3 -CH=CH-CH3 H2O / H+ B + C37

-C-H

A

ALCOHOL REACTIONS(a) As an acid In an aqueous solution alcohol reacts as a very weak acid ROH + H2O RO- + H3O+

Reacts with Na or NaH & form a very strong base alkoxide ion CH3CH2OH + Na CH3CH2O-Na+ + 1/2H2

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ALCOHOL REACTIONS(a) As a base With the presence of lone pair of e- at the O atom, alcohol can accept proton from an acid

CH3CH2-O-H + HA

CH3CH2O+-H + AH

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ALCOHOL REACTIONS(1) Esterification Alcohol reacts with carboxylic acid under reflux & is catalysed by mineral acids (H2SO4 or HCl) General reaction:O H+ , O

R-C-OH + R-OHacid alcohol

R-C-OR + H-O-Hester water40

ALCOHOL REACTIONS(1) Esterification Example:O H+ , O

CH3C-OH + CH3-OHethanoic acid methanol

CH3C-OCH3 + H-O-Hmethyl ethanoate

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ALCOHOL REACTIONS(1) Esterification Alcohol reacts with acyl chloride to form esterO base O

CH3C-Cl + CH3-OHethanoil chloride methanol

CH3C-OCH3 + HClmethyl ethanoate

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ALCOHOL REACTIONS(2) Dehydration of alcohol Involve formation of carbocation Possible of rearrangement CH3CH2CH2OHpropanol H2SO4(con .) 1800 C

CH3CH=CH2propene

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ALCOHOL REACTIONS(3) Formation of haloalkane ROH reacts with HX to form RX The reaction rates are in the order HI > HBr > HCl (HF non-reactive) Reactivity of alcohols 3o ROH > 2o ROH > 1o ROH > phenol

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ALCOHOL REACTIONSExample:-

ROH + HX

RX + H2O

CH3CH2CH2OH + HBr

CH3CH2CH2Br + H2O

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ALCOHOL REACTIONS(3) Formation of haloalkane ROH reacts with PX3, PX5 , SOCl2 General reaction: (i) 3ROH + PX3 (ii) ROH + PCl5 (iii)ROH + SOCl2 3RX + H3PO3 RCl + POCl3 + HCl RCl + SO2 + HCl

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ALCOHOL REACTIONS(4) Oxidation of alcohols Common oxidising agents are potassium permanganate (KMnO4/H+) and potassium dichromate (K2Cr2O7/H+) Oxidation product depends on the class of alcohol used

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ALCOHOL REACTIONS(4) Oxidation of 1o alcohol 1o R-OH can be oxidised to give an aldehyde. Further oxidation would give a carboxylic acid O RC-Haldehyde

RCH2OH1o alcohol

[O]

[O]

O RC-OHcarboxylic acid

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ALCOHOL REACTIONS(4) Oxidation of 1o alcohol Example:CH3CH2OHK2Cr2O7/H+

O CH3C-H

K2Cr2O7/H+

O CH3C-OH + Cr

3 +

orange

green

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ALCOHOL REACTIONS(4) Oxidation of 1o alcohol Sarett-Collins reagent is a special oxidation agent to change a 1o alcohol to an aldehyde CrO3 is added to excess pyridine to form pyridinium chlorochromate (PCC) CH3CH2CH2OH + PCCpropanol

O CH3CH2C-Hpropanal50

ALCOHOL REACTIONS(4) Oxidation of 2o alcohol form ketone which cannot be oxidised further under normal conditions R RCH-OH2o alcohol [O]

R RC=O + H2Oketone

CH CH KMnO4/H 3 3 CH3CH-OH + CH3C=O + H2O2-propanol propanone51

ALCOHOL REACTIONS(4) Oxidation of 3o alcohol Does not undergo oxidation under normal condition R R-C-OH R3o alcohol

[O]

no reaction

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Chemical test for R-OH Lucaso

test(con.) 2

Lucas reagent : HCl + ZnCl 3 R-OH + Lucas reagent reacts

immediately to form cloudy haloalkane 2o R-OH + Lucas reagent takes about 5-10 minutes 1o R-OH + Lucas reagent no visible changes unless heated

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Example:

OBSERVATIONS :

CH2OH HCl / ZnCl2Does not turn cloudy

OH HCl / ZnCl 2Turn cloudy within 5 minute54

CH3 OH HCl / ZnCl2

OBSERVATIONS : Turn cloudy immediately

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Haloform Reaction

Methyl carbinol cleavage to give Carboxylic acids and HaloformH CH 3 C H OH H CH 3 C R OH X2 ,H+ OH HCX 3 + H C OH O

X2 ,H+ OH

HCX 3 + R

C OH O56

IODOFORM TESTOH

CH3CH2CCH3 + 3I2 2-butanol CH3CH2COO- + CHI3 yellow precipitate (iodoform)57

base (OH-)

PHENOLManufacture of phenol by Cumene process(a) Friedel-Crafts reaction CH3-CH-CH3 + CH3CH=CH2AlCl3

Isopropylbenzene (cumene)58

PHENOL(b) Oxidation of Cumene CH3-CH-CH3 + O21200C

O -OH CH3-C-CH3Cumene hydroperoxide

(c) Decomposition & rearrangement CH3 -C-O-OH CH359

H2SO4

O -OH + CH3CCH3

Phenol reactions1. Reaction at functional group -OH(a) Reaction with Na OH + Na O-Na+ + H2

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Phenol reactions1. Reaction at functional group -OH(b) Reaction with NaOH OH + NaOH O-Na+ + H2O no reaction

CH3CH2OH + NaOH

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Phenol reactions2. Electrophilic substitution reactions(a) Halogenation (Bromination)-OH is ortho-para director in Br2, aqueous solution, white precipitate 2,4,6tribromophenol will form

OH Br + 3Br2 / H2O

OH Br + 3HBr Br62

Phenol reactions2. Electrophilic substitution reactions(a) Bromination to get monobromination (catalyst: FeBr3 or CS2) OH + Br2 CS2 50C Br63

OH +

OH Br + HBr

Phenol reactions2. Electrophilic substitution reactions(b) NitrationOH Dilute HNO3 Room temp. NO2 OH O2NConcentrated HNO3

OH NO2 +

OH

NO2Yellow precipitate

NO264

Phenol reactions3. Esterificationphenol is a weaker nucleophile than alcohol since the lone pair e- of O atom are delocalised to the benzene ring reacts with an acid derivative such as acid chloride to form an ester CH3 OH O-C=O Cl + CH3-C=O + Cl65

Phenol reactions4. Identification test for phenolsphenol reacts with aqueous solution of iron (III) chloride giving a light purple complex OH + FeCl3(aq)Purple complex

OH

FeCl3

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EXERCISE 1 Suggest a chemical test to differentiate the following pairs of compounds. State the reagents, observations and write chemical equations involved. (a) methanol from ethanol (b) 2-methyl-1-propanol from 2-methyl-2-propanol (c) cyclohexanol from cyclohexane (d) phenol from benzyl alcohol (e) o-methylphenol from 2-methylcyclohexanol

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EXERCISE 2 Compound A (C4H10 O) undergoes oxidation to form compound B (C4H8O). Oxidation of B gives compound C (C4H8O2). Reaction of A with hot concentrated sulphuric acid yields compound D (C4H8). Hydration of D gives compound E (C4H10 O) which cannot be oxidised. A and E are isomeric. Suggest the structure of A, B, C, D and E. Rasionalise your answer.

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Common used of alcohol and phenol Ethyl

alcohol is a poison. LD50 = ~10g/Kg orally in mice.- Nausea, vomiting, flushing, mental excitement or depression, drowsiness, impaired perception, loss of coordination, stupor, coma, death may occur. (intoxication) Phenol is an important industrial chemical. Major use is in phenolic resins for adhesives and plastics.69

Phenols in Medicine

Many phenols are used as antiseptics and disinfectants. OH OH OH

OH

OH CH2CH2CH2CH2CH2CH3

Phenol

Resorcinol (antiseptic)

4-Hexylresorcinal (antiseptic)70

Derivatives of Phenol

Compounds of phenol are the active ingredients in the essential oils of cloves, vanilla, nutmeg, and mint.

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