See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1 (Identify the parent structure): The molecule contains a benzene ring, which is the aromatic parent hydrocarbon. Step 2 (Identify the substituent): Attached to the benzene ring is a -CH=CH2 group, which is a vinyl (ethenyl) group — a two-carbon chain with a terminal double bond. Step 3 (Apply IUPAC nomenclature): When a vinyl group is attached to a benzene ring, the IUPAC name is formed by combining 'ethenyl' (the substituent name for -CH=CH2) with 'benzene' as the parent. This gives 'ethenylbenzene'. The common name for this compound is styrene, but the IUPAC systematic name is ethenylbenzene. Step 4 (Verify): The structure shown is a benzene ring with a -CH=CH2 group directly bonded to it, which matches ethenylbenzene perfectly. No other substituents are present, so no locant numbers are needed. Therefore, the correct answer is ethenylbenzene.