See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the structure. The compound is CH3—CO—CH(CH3)—CH2—CH2Cl. It contains a ketone (C=O) group and a terminal chloromethyl group, with a methyl branch. Step 2: Identify the longest carbon chain containing the principal characteristic group (ketone). The chain is: CH3—CO—CH—CH2—CH2Cl, which gives 5 carbons (including the carbonyl carbon). The methyl group on C3 is a substituent. Step 3: Number the chain to give the principal characteristic group (ketone) the lowest possible locant. Numbering from the CH3 end (left): C1=CH3, C2=CO, C3=CH(CH3), C4=CH2, C5=CH2Cl. The ketone is at C2, and if numbered from the other end, the ketone would be at C4. So numbering from the left gives the ketone the lower locant (C2). Step 4: Identify substituents and their positions. With the numbering C1–C5: ketone at C2 (pentan-2-one), methyl branch at C3 (3-methyl), chloro at C5 (5-chloro). Step 5: Construct the IUPAC name. Parent chain: pentane (5 carbons). Principal group: ketone at position 2 → pentan-2-one. Substituents: 3-methyl, 5-chloro. Alphabetical order: chloro before methyl. Full name: 5-Chloro-3-methylpentan-2-one. Step 6: Evaluate other options. (a) 1-Chloro-3-methylpentan-4-one places the ketone at C4, giving a higher locant than necessary. (b) 1-Chloro-2-(oxoethylbutane) is not a valid IUPAC name format. (d) 3-(2-Chloroethyl)butan-2-one would imply a 4-carbon parent chain with a 2-chloroethyl substituent, which misrepresents the structure. Therefore, the correct answer is C.