Question

Which of the following is not a reason for carboxylic acids having higher boiling point than alcohols of comparable molecular masses?

(a) Presence of electron withdrawing carbonyl group

(b) Higher polarity of OH bond than in alcohols

(c) Formation of two hydrogen bonds to form cyclic dimers

(d) Presence of more alkyl groups in carboxylic acids

The question was posed to me during an online interview.

Enquiry is from Carboxylic Acids Physical Properties topic in section Aldehydes, Ketones and Carboxylic Acids of Chemistry – Class 12

Answer 1

Correct option is (d) Presence of more alkyl groups in carboxylic acids

The explanation: The OH bond in carboxylic acids is more strongly polarised due to the presence of adjacent electron withdrawing CO group. This results in stronger hydrogen bonds. Also, the presence of alkyl groups should increase the polarity of OH bond as they are electron releasing in nature. Furthermore, carboxylic acids form two hydrogen bonds between molecules compared to the only one between alcohols.