Question

Why are acid anhydrides acidic?

Answer 1

Because they form carboxylic acids in aqueous solution, and these are proton donors.

Explanation:

Acid anhydrides are essentially two carboxylic acid molecules, joined together by a condensation reaction between the two -COOH groups to form -COOCO- and eliminate water. They react readily with water to form two carboxylic acids again, so in the presence of water, the acid anhydride is hydrolysed and forms carboxylic acids again and these release `H^+(aq)` ions into the solution.