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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
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