See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Step 1 - Identify Structure 1: The first structure is a five-membered ring with a nitrogen atom bearing an N-H, flanked by two carbonyl groups (C=O on both sides of N). This is the defining feature of an imide: R-CO-NH-CO-R in cyclic form. This compound is succinimide, a classic cyclic imide. Step 2 - Identify Structure 2: The second structure is a five-membered ring with a nitrogen atom bearing an N-H and only one carbonyl group adjacent to the nitrogen. A cyclic amide is called a lactam. This compound is 2-pyrrolidinone (gamma-lactam), a classic lactam. Step 3 - Identify Structure 3: The third structure is a five-membered ring with an oxygen atom and one carbonyl group adjacent to the oxygen. A cyclic ester is called a lactone. This compound is gamma-butyrolactone, a classic lactone. Step 4 - Match to options: Structure 1 = Imide, Structure 2 = Lactam, Structure 3 = Lactone. This corresponds to option (d): Imide, Lactam, Lactone. Step 5 - Why other options fail: - (a) calls Structure 1 an Anhydride, which is incorrect; an anhydride has two acyl groups linked by an oxygen, not a nitrogen. - (b) calls Structure 1 a Lactam and Structure 2 an Imide, which reverses the correct assignments. - (c) calls Structure 2 a Lactone and Structure 3 an Anhydride, both incorrect. Therefore, the correct answer is D.