See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the parent ring: The structure shows a five-membered carbocyclic ring with two double bonds. Numbering the ring, the double bonds are at positions 1,2 and 3,4, making the parent compound cyclopenta-1,3-diene. Step 2 - Identify the substituent: Attached to C5 (the sp3 carbon of the ring) is a three-carbon chain ending in a terminal double bond: -CH2-CH=CH2. This is an allyl group, systematically named prop-2-en-1-yl (or prop-2-enyl). Step 3 - Assign the locant: C5 is the only saturated carbon in cyclopenta-1,3-diene, and the substituent is attached there, so the locant is 5. Step 4 - Assemble the IUPAC name: substituent name + parent name = 5-(prop-2-enyl)cyclopenta-1,3-diene. Step 5 - Verify: No other regiochemistry is possible because only one carbon in the ring lacks a double bond, confirming the locant 5 and the name. Therefore, the correct answer is 5-(prop-2-enyl) cyclopenta-1,3-diene.