See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution **Step 1: Identify the starting material** The starting diol has two cyclopentanone rings connected by a single C–C bond, with hydroxyl groups on adjacent carbons (vicinal diol arrangement). **Step 2: Recognize the reaction conditions** Concentrated $H_2SO_4$ is a strong dehydrating agent that acts as both an acid catalyst and water-removing reagent. **Step 3: Mechanism of dehydration** - The vicinal diol is protonated by $H_2SO_4$ - Water is eliminated from one hydroxyl group - This generates a carbocation intermediate at the junction between the two rings **Step 4: Carbocation rearrangement** The carbocation undergoes a **ring expansion** via a 1,2-hydride shift: - The five-membered ring expands to a six-membered ring - This produces a more stable secondary carbocation **Step 5: Cyclization and deprotonation** The remaining hydroxyl group attacks the carbocation intramolecularly, forming a new C–O bond and creating a bicyclic ketone structure. **Step 6: Product identification** The major product is a bicyclic compound consisting of a fused hexane–pentanone ring system with a ketone at the junction — this corresponds to **option (A)**. **Answer: (A)** is correct because ring expansion via acid-catalyzed dehydration and rearrangement of the vicinal diol produces the most thermodynamically stable bicyclic ketone.