Alcohol Functional Group


 
 
Concept Explanation
 

Alcohol Functional Group

Alcohols:

Alcohols are the group of the organic compounds which contains carbon, hydrogen and oxygen.These are obtained by replacement of one hydrogen atom with the hydroxy group.

Classification of Alcohols: 

 Alcohols are classified according to number of hydroxyl groups present in their molecule. Alcohols with one, two and three hydroxyl groups are called monohydric, dihydric & trihydric alcohols respectively. Alcohols which contains four or more hydroxyl groups are called polyhydric alcohols.

  H_3C-OH, ; ; (CH_2OH)_2, ; ; (CH_2OH)_3, ; ; (CH_2OH)_4

       Methanol           Ethylene glycol       Glycerol              Butane - 1,2,3,4- tetrol

Monohydric alcohols are further divided into three classes :

(i)  Primary alcohol : The hydroxyl group is attached with primary carbon atom. They possess a characteristic group -CH_2OH

                                                CH_3CH_2CH_2OH

(ii) Secondary alcohol : The hydroxyl group attached to secondary carbon atom. They possess >CH-OH group.

                                            (CH_3)_2CHOH

                                             Propane - 2 - ol

(iii)  Tertiary alcohol : The hydroxyl group attached to tertiary carbon atom. They possess a characteristic group C - OH.

                                         (CH_3)_3COH

                                          2 - Methyl propan - 2 - ol

Physical Properties:

1. The first two  members of alcohol; methanol and ethanol, are volatile liquids.

2. All alcohols are neutral to indicators.

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Sample Questions
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Question : 1

Which of the following are correct :

(a) The boiling point of alcohols increases as their molecular mass increases.

(b) Alcohols are poor conductors of electricity because hydrogen in the hydroxyl group does not ionize.

Right Option : C
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Question : 2

Alcohol react with metallic sodium to liberate ____________________________.

Right Option : A
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Question : 3

Which of the following are correct :

(a) Alcohols react with acids to form esters.

(b) The first two members of alcohol; methanol and ethanol, are volatile liquids.

(c) Alcohols which contains four or more hydroxyl groups are called polyhydric alcohols.

Right Option : D
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