Q.48. Select the CORRECT increasing order of boiling points of alcohols, amines and carboxylic acids of comparable molar mass from the following.
A. Alcohols < Amines < Carboxylic acids
B. Amines < Carboxylic acids < Alcohols
C. Amines < Alcohols < Carboxylic acids
D. Carboxylic acids < Alcohols < Amines
Answer :- C. Amines < Alcohols < Carboxylic acids
Explanation :-
N−H bonds in amines are less polar than O−H bond in alcohols. Carboxyl group (−COOH) of carboxylic acid contains O−H bond which is responsible for formation of hydrogen bonding. Strength of hydrogen bonding in carboxylic acid is greater than that of alcohols.
The O−H bond in carboxylic acid is polarized to a great extent as compared to alcohol. Hence, they have higher boiling points than corresponding alcohols.