See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the parent structure. The compound contains a benzene ring, which serves as the parent hydrocarbon (benzene). Step 2: Identify the substituents. There are two substituents on the benzene ring: - A methyl group (-CH3) at one position - A vinyl (ethenyl) group (-CH=CH2) at the para position relative to the methyl group Step 3: Assign the principal characteristic group / highest-priority substituent for numbering. In IUPAC nomenclature, when naming as a substituted benzene, the substituents are given the lowest possible locants. The vinyl (ethenyl) group is treated as the principal substituent when naming as an ethenylbenzene derivative, or we can name it as a disubstituted benzene. Step 4: Number the ring to give lowest locants. Placing the ethenyl group at C-1 and the methyl group at C-4 gives locants 1 and 4, which is the lowest set. Step 5: Construct the name. The compound is named as a benzene with an ethenyl group at position 1 and a methyl group at position 4: 1-ethenyl-4-methylbenzene. Substituents are listed alphabetically (ethenyl before methyl). Step 6: Verify. The structure shows a para-substituted benzene with vinyl and methyl groups, consistent with 1-ethenyl-4-methylbenzene (also known commonly as 4-vinyltoluene or p-methylstyrene). Therefore, the correct answer is 1-ethenyl-4-methylbenzene.