Chemistry

Organic Compounds with Functional Groups Containing Oxygen-II

Session

Session Objectives

1. Preparation of methanol and its properties

2. Preparation of ethanol and its properties

3. Preparation of ethylene glycol and its properties

4. Preparation of glycerol and its properties

5. Preparation of phenol

Methanol

Preparation

1. From destructive distillation of wood

2. By catalytic hydrogenation of carbon monoxide.

2 3Cu Zn Cr O2 3CO 2H CH OH

Pyroligneous acid obtained from destructive distillation of wood consists of 5% methyl alcohol

3. From natural gas

oCu / 250 C,100 atm

4 2 3CH 2O CH OH

Properties of methanol

Colourless liquid.

Highly poisonous in nature; as little as 30 ml can cause death.

As a solvents in paints, varnishes.

Chiefly for making formaldehyde.

As an antifreeze for automobile radiators.

To denature ethyl alcohol.

20% mixture of methyl alcohol and gasoline makes a good motor fuel.

Uses

Ethanol

Fermentation of sugar

Invertase12 22 11 2 6 12 6 6 12 6

Glucose Fructose

Zymase6 12 6 2 5 2

C H O H O C H O C H O

C H O 2C H OH 2CO

Fermentation stops when alcohol formed is more than 14 percent due to the acidic nature of the alcohol.

Synthesis of alcohol

o

3 4H PO / 300 C, 60 atm2 4 2 2 5

EthyleneC H H O C H OH

Important reactions

Reaction with sulphuric acid:(i) At room temperature

C2H5OH + H2SO4 C2H5OSO2OH + H2O(ii) At 140oC

C2H5OH + H2SO4 C2H5OC2H5 + H2O(iii) At 170oC

C2H5OH + H2SO4 C2H4 + H2O

Reaction with alumina:

2 3Al O , 350 C2 5 2 2C H OH CH CH

2 3Al O , 200 C2 5 2 5 2 5C H OH C H OC H

Specific reactions

Reduction

P,2 5 2 6 2 2C H OH 2HI C H I H O

oxidation

2 2 7 2 2 7Na Cr O /H Na Cr O /H2 5 3 3C H OH CH CHO CH COOH

Formation of iodoform

2 5 2 3C H OH 4I 6KOH CHI HCOOK 5KI

Cu, 300 C2 5 3 2C H OH CH CHO H

Uses of ethyl alcohol

Manufacturing of alcoholic beverages.

As an industrial solvent.

Manufacturing drugs, flavouring extracts, and perfumes.

As an antiseptic in hospitals.

In manufacturing of synthetic rubber.

Absolute alcohol

100% pure ethyl alcohol

Commercial alcohol is 95% ethyl alcohol.Because at this composition water and alcohol formed azeotropic mixture,it cannot separated by further distillation.

Method to obtain absolute alcohol

Laboratory method:Quicklime is added to the commercial alcohol. The mixture is refluxed for 8 hours. It is then distilled to give absolute ethyl alcohol.CH3CH2OH + H2O + CaO CH3CH2OH + Ca(OH)2.

Industrial method:Commercial alcohol is extracted with benzene. Distillation this gives absolute alcohol at 78oC.

Denatured alcohol

Mixture of commercial ethyl alcohol with small amount of very poisonous substances.

Alcoholic beverages.Heavy excise duty

For industrial purposes, it is duty free.

Denatured

Alcoholic beverages

Wine 12% ethyl alcohol.Beers 4% ethyl alcohol.Whiskey 40-50% ethyl alcohol.Brandy 40-50% ethyl alcohol.

Content of ethyl alcohol in beverages is indicated by ‘Proof Spirit’Proof is the double of volume of ethyl alcohol in beverages.

Preparation of ethylene glycol

1. By oxidation of ethylene with cold dilute potassium permanganate solution.

C H2

C H2

+ H O + O24

C H O H2

C H O H2

2. By hydrolysis of 1,2-dibromoethane with aqueous sodium carbonate solution.

C H B r2

C H B r2

+ H O2

C H O H2

C H O H2

N a C O2 3 +

Preparation of glycol

3. By hydrolysis of ethylene oxide with H2O at 200oC under pressure or with dilute H2SO4 at 60oC.

H O2

C H O H2

C H O H2

+C H2 C H2

O

H

60oC

+

Properties of glycol

It’s a colourless viscous liquid, b.p 197oC.

It has a sweet taste.

It is hygroscopic.

Soluble in ethanol and water.

Toxic as methyl alcohol when taken orally.

Reactions with sodium

It shows all the reactions of –OH group. Due to two –OH group it consumes more reactants. Sometimes more drastic conditions are require to react with second –OH group of ethylene glycol. For example

C H O H2

C H O H2

H C l

160 Co

C H C l2

C H O H2

H C l

200 Co

C H C l2

C H C l2

It is used as coolent in automobiles and synhetic fibres like dacron, polyester used for making wrinkle free clothes.

Oxidation of glycol

C H O H2

C H O H2

C H O H2

C H O

C H O H2

C O O H

C H O

C H O

C H O

C O O H

C O O H

C O O H

O xa lic A c idG lyoxa lic ac id

E thyleneg lyco l

G lyco lica ldehyde

G lyco licacid

G lyoxa l

(i). Nitric acid yields a number of substances.

(ii) With acidic potassium permanganate or potessium dichromate gives formic acid.

(iii). Periodic Acid Cleavage of Glycols

C H O H2

C H O H2

K M nO4H C O H

O

H + H C

OH

H

C

OH

H

H HIO4+HIO3

HIO4+HIO3C

OH

H

C

OH

H

R R

HIO4+HIO3C

OH

C

OH

R R

R' R'

H C H

O

2

2 C H

O

R

2 C

O

R R'

Dehydration of ethylene glycol

C H O H2

C H O H2

C H2 C H2

O

H2SO4;

CH3CHO

;ZnCl2

C H2 C H2

OO

C H2 C H2

D ioxane

H2SO4;

; 500oCC H 2 C H 2

O

C H2 C H 2

D iethyleneg lyco l

H O

H O

Propane-1,2,3-triol(Glycerol)

Preparation

1. From fats and oils: by product of soap industry.

C H O O C R2

C H O O C R

C H O O C R2

+ 3N aO H

C H O H2

C H O H

C H O H2

+ 3R C O O N a

F a t o r o il G lyce ro l

S oap

This reaction is called saponification.

Properties

Colourless, odourless sweet tasting and syrup liquid,

b.p. 290oC.

It is nontoxic.

Soluble in water and ethanol.

It is hygroscopic, i,.e., absorbs moisture from air.

Reaction with nitric acid

Gives nitroglycerine; pale yellow oily liquid;

C H O H2

C H O H

C H O H2

+ 3H N O

C H O2

C H O

C H O2 N O2

N O2

N O23

a powerful explosive.

Reaction with hydrogen iodide

With small amount of HI

With large amount of hydrogen iodide.

H I

C H 2

C H

C H I2

C H 3

C H I

C H I2

C H 3

C H

C H 2

H I

C H 3

C H I

C H 3

-I2

C H O H2

C H O H

C H O H2

+3H I

C H I2

C H I

C H I2

C H 2

C H

C H I2

-I2

Reaction with oxalic acid

At 110oC, gives glyverol monoformate.

110oCC O O H

C O O H

O

C H O H2

C H O H

C H O H2

+

C H O C H2

C H O H

C H O H2

At 260oC, gives allyl alcohol.

110oC

O O C

O O C

C H O H2

C H O H

C H O H2

+

C H 2

C H

C H O H2

C H 2

C H

C H O H2

H O O C

H O O C

-CO2

Oxidation

Two primary alcohol groups in glycerol are capable of being oxidized to the aldehydes and then the carboxyl group. The secondary alcohol group can be oxidized to the carbonyl group.

Variety of oxidation products obtained depending on the nature of the Oxidising agent.

a. With dilute HNO3 gives glyceric acid and tartonic acid.

b. With concentrated HNO3 gives mainly glyceric acid.

c. With bismuth nitrate gives mainly mesoxalic acid.

d. With bromine water, sodium hypobromite, or Fenton’s reagent

(FeSO4+H2O2), gives a mixture of glyceraldehyde and

dihydroxyacetone.

e. With periodic acid gives fornaldehyde and formic acid.

2

C O H 2

C O

C O H

Dehydration

When heated alone or with KHSO4 two molecules of water eliminates.

C H O H2

C H O H2

C H O H2

K H S O4C H 2

C H

C H O

Phenol

Containing —OH group attached directly to an aromatic ring.

Compounds which contain an —OH group in a side chain attached to anb aromatic ring are not phenols. They are called aromatic alcohol. For example

O H

P heno l

O HC H3

o-C reso l

O H

O HQ u ino l

C H O H2

B enzyl a lcoho l

Preparation of phenol

From aryl sulphonic acids

S O H3

+ N aO H

S O N a3 O N a O H

H+

Aryl sulphonic acid gives corresponding phenol on heating with molten sodium hydroxide at 570-620 K.

Preparation of phenol

+ N aO H

O N a O H

H+

C l

623 K

320 atm

Chlorobenzene is hydrolysed by treating it with NaOH at 623 K and 320 atm.

Preparation of phenol

From hydrolysis of diazonium salt

Diazonium salts are prepared by treating an aromatic primary amine with nitrous acid (NaNO2 + HCl) at low temperature.

O HN H

P heno l

NaNO + HCl

2

2

N C l2

+ –

H O2

B enzened iazon iumchlo ride

Preparation methods

Synthesis from cumene

2O

OH3

C CH3CH3

O OH

OH

CH3 C CH3

O

CHCH3CH3

+

By decarboxylation of salicylic acid with soda lime

OH

COOH

ONa OH

+ 3NaOHCaO, 360 K

-Na2CO3, -2H2O

HCl

-NaCl

Thank you