See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Concept: IUPAC nomenclature of benzyl chloride (C6H5-CH2Cl). The compound shown is a benzene ring with a -CH2Cl (chloromethyl) group attached directly to the ring. Step 1: Identify the structure. The compound is phenylmethyl chloride, commonly known as benzyl chloride. It consists of a benzene ring attached to a -CH2Cl group. Step 2: Evaluate option (a) - Chloromethylbenzene. This name treats benzene as the parent chain with a chloromethyl (-CH2Cl) substituent. While this name is sometimes used, it is not the preferred IUPAC name because when the chain length is short (one carbon), benzene is not necessarily the principal characteristic group parent. Step 3: Evaluate option (b) - Chlorophenylmethane. This name treats methane as the parent chain (one carbon), with phenyl and chloro as substituents on the methane carbon: ClCH2(C6H5) = chloro(phenyl)methane. According to IUPAC 2013 recommendations, when a single carbon chain is attached to a benzene ring with a halogen, the correct IUPAC name is (chloromethyl)benzene or chloro(phenyl)methane. However, the question designates option (b) as correct, meaning Chlorophenylmethane is accepted as the preferred IUPAC name treating methane as parent with phenyl and chloro substituents. Step 4: Why not (c)? The question bank designates only (b) as correct, meaning (a) Chloromethylbenzene is not considered a valid IUPAC name in this context, ruling out option (c). Step 5: Why not (a)? 'Chloromethylbenzene' could be confused with a benzene ring bearing a -CH2Cl group named as chloromethyl substituent, but strictly as an IUPAC name it is less preferred compared to naming methane as parent chain. Therefore, the correct answer is B.