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Hydroxy Compounds (Alcohols)

Alcohol Phenol And Ether of Class 12

Monohydric i.e.

Hydroxy Compounds (Alcohols)

Dihydric

Hydroxy Compounds (Alcohols)

Polyhydric

Hydroxy Compounds (Alcohols)

Contain three and more than three hydroxyl group.

Monohydric alcohols are of three types.

Hydroxy Compounds (Alcohols)

PREPARATION OF ALCOHOLS

1. From Alkanes

Alkanes having tertiary carbon on oxidation with cold alkaline KMnO4 give tertiary alcohol.

Hydroxy Compounds (Alcohols)

2. From Alkenes

Alkenes can be converted into alcohol by the following reactions:

Hydroxy Compounds (Alcohols)

3. From alkyl halides

Alkyl halides give alcohol with KOH/NaOH or with moist Ag2O.

Hydroxy Compounds (Alcohols)

4. Reduction of aldehydes and ketones

(a) Reduction by reducing agents

(i) Aldehyde gives primary alcohol

Hydroxy Compounds (Alcohols)

(ii) Ketone gives secondary alcohol

Hydroxy Compounds (Alcohols)

Reducing agents

(ii) LiAlH4 (ii) NaBH4

(iii) Na/C2H5OH (iv) Metal (Zn, Fe or Sn)/Acid (HCl, dil H2SO4 or CH3COOH)

(v) (a) Aluminium isopropoxide/isoproppylalcohol (b) H2O

(vi) H2/Ni

NaBH4 and aluminium isopropoxide reduces only carbonyl group and has no effect on any other group.

Hydroxy Compounds (Alcohols)

Reducing with aluminium isopropoxides is known as Meerwein – Ponndorf Verley (MPV) reduction.

LiAlH4 has no effect on double and triple bonds but if compound is β - aryl, α, β - unsaturated carbonyl compound then double bond also undergoes reduction.

Hydroxy Compounds (Alcohols)

Hydroxy Compounds (Alcohols)

(b) Reduction by Grignard reagents

Addition followed by hydrolysis

Hydroxy Compounds (Alcohols)

Methanol can not be prepared by this method.

5. Reduction of carboxylic acid, Acid chlorides and esters:

(a) Reduction by LiAlH4

Hydroxy Compounds (Alcohols)

G = OH (acid)

G = Cl (acid chloride)

G = OR′ (ester)

(b) Reduction by BH3

Carboxylic acids and esters are reduced in to primary alcohol by BH3.

Hydroxy Compounds (Alcohols)

Hydroxy Compounds (Alcohols)

(c) Bouveault – Blanc reaction

Hydroxy Compounds (Alcohols)

6. From aliphatic primary amines

It react with nitrous acid to give alcohol.

Nature of alcohol depends on the nature of carbon having ⎯NH2 group.

Reaction proceeds through carbocation hence rearranged alcohol is obtained.

Hydroxy Compounds (Alcohols)

7. From Oxiranes

Oxiranes react with Grignard reagent to give mono hydric alcohol. Nature of G.R is basic hence it attack on less hindered carbon of oxirane ring.

Hydroxy Compounds (Alcohols)

8. Fermentation of carbohydrates

Hydroxy Compounds (Alcohols)

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