See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the parent chain/ring: The structure contains a five-membered carbocyclic ring, making it a cyclopentane derivative. Step 2 - Identify the principal characteristic group: Attached to one carbon of the ring is a -C(=O)-NH2 group, which is an amide (carboxamide) functional group. Because the carbonyl carbon is exocyclic (not part of the ring), the compound is named as a cyclopentane carboxamide (using the 'carboxamide' suffix for an exocyclic -CONH2 group attached to a ring). Step 3 - Identify substituents: A methyl group (CH3) is attached to the carbon adjacent to the carbon bearing the carboxamide group. Step 4 - Number the ring: The carbon bearing the principal characteristic group (carboxamide) receives the lowest possible locant; it is C-1. The adjacent carbon carrying the methyl group is therefore C-2. Step 5 - Construct the IUPAC name: Parent ring = cyclopentane; exocyclic amide suffix = carboxamide; methyl substituent at C-2 → 2-methylcyclopentane-1-carboxamide, commonly written as 2-methylcyclopentane carboxamide. No other options are provided to eliminate, but alternative incorrect names such as 'methylcyclopentanamide' would fail because they imply the nitrogen or ring carbon is the amide carbon rather than an exocyclic one. Therefore, the correct answer is 2-methylcyclopentane carboxamide.