Question

Give reason of the following
Carboxylic acids have higher boiling point than alcohols of comparable molecular masses. 
 

Hint:

Carboxylic acid boiling points are even higher than those of alcohols because of the formation of "cyclic dimers".

Answer 1

Step 1: Understanding the Concept:
Boiling point depends on the strength of intermolecular forces, primarily hydrogen bonding in polar organic compounds.
Step 2: Detailed Explanation:
Carboxylic acids form stronger intermolecular hydrogen bonds than alcohols.
In carboxylic acids, the molecules exist as cyclic dimers even in the vapor phase.
Each pair of acid molecules is held together by two hydrogen bonds, creating a stable eight-membered ring.
Alcohols form only single hydrogen bonds between molecules.
More energy is required to break these extensive dimeric structures in acids, resulting in a higher boiling point.
Step 3: Final Answer:
The higher boiling point of carboxylic acids is due to more extensive association via hydrogen bonding (dimerization).