Solution

A dicarboxylic acid capable of forming a stable 5- or 6-membered cyclic anhydride on heating (and a corresponding cyclic imide on strong heating with ammonia) is one whose two $-COOH$ groups are positioned close enough (e.g. succinic acid-type structure) to allow intramolecular cyclisation.

Concept Reactions of dicarboxylic acids - anhydride and imide formation

Aldehydes, Ketones and Carboxylic Acids in past papers

91 questions from this chapter have appeared across 27 exam years.