See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the ring system: The structure shows a five-membered carbocyclic ring, which is a cyclopentane-based ring. Step 2 - Identify the degree of unsaturation within the ring: The ring contains two carbon-carbon double bonds, making it a cyclopentadiene (cyclopenta-1,3-diene) skeleton. Step 3 - Locate the substituent: A hydroxyl group (-OH) is directly attached to one of the sp2 (doubly bonded) carbon atoms of the ring. Specifically, it is on C1, which is part of the conjugated diene system. Step 4 - Apply IUPAC nomenclature: The parent chain is cyclopenta-1,3-diene (a five-membered ring with double bonds at positions 1-2 and 3-4). The -OH group is at C1, giving the suffix -ol. The compound is therefore named cyclopenta-1,3-dien-1-ol. Step 5 - Confirm the name: The -OH is on a vinyl (sp2) carbon, making this an enol-type compound within a cyclic diene framework. The lowest locants rule places the OH at position 1, with the double bonds at 1,2 and 3,4 positions, fully consistent with the name cyclopenta-1,3-dien-1-ol. Therefore, the correct answer is cyclopenta-1,3-dien-1-ol.