See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the parent chain and functional group. The molecule contains a ketone (C=O) group. We need to find the longest carbon chain that includes the carbonyl carbon. Step 2: Count the carbons in the longest chain including the carbonyl. Starting from the methyl group on the left of the carbonyl: CH3-C(=O)-CH2-CH(CH3)-CH3. Wait, let us re-examine the structure. The image shows CH3-CH(CH3)-CH2-C(=O)-CH3, which has the ketone near the right end. Step 3: Identify the longest chain. The main chain includes: CH3 (C1) - C=O (C2) - CH2 (C3) - CH(CH3) (C4) - CH3 (C5), giving a 5-carbon chain with a branch. But we number to give the ketone the lowest locant. Numbering from the ketone end: C1=CH3, C2=C=O, C3=CH2, C4=CH(CH3), C5=CH3. This gives the ketone at position 2 and the methyl branch at position 4. Step 4: Name the compound. The parent chain is pentane (5 carbons), the ketone is at C2 (pentan-2-one), and there is a methyl substituent at C4 (4-methyl). Combined: 4-methylpentan-2-one. Step 5: Verify. The molecular formula matches: C6H12O. The IUPAC name 4-methylpentan-2-one correctly describes a 5-carbon chain with a ketone at C2 and a methyl group at C4. Therefore, the correct answer is 4-methylpentan-2-one.