Ozonolysis of cyclic alkenes does not change the total number of carbon atoms.
Counting the total carbons in the product (6 carbons) and knowing it closed to a 5-membered ring with a methyl branch immediately rules out 3-methylcyclopentene and 1-methylcyclohexene.
1-Methylcyclopentene (with double bond at C1-C2, methyl at C1)
3-Methylcyclopentene
1-Methylcyclopentene (alternative orientation)
1-Methylcyclohexene
Show Solution
The Correct Option isC
Solution and Explanation
Step 1: Recall what reductive ozonolysis does. It cleaves a C=C double bond and turns each end into a C=O group, so working backwards from the carbonyl product reveals exactly where that double bond used to sit. Step 2: Look at the given product. It's 5-oxohexanal, $\text{CH}_3-\text{CO}-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CHO}$, a six carbon chain with a ketone at one end and an aldehyde at the other. Step 3: Rebuild the ring. Join the ketone carbon back to the aldehyde carbon with a double bond, closing a five-membered ring and leaving a methyl group on the carbon that used to carry the ketone. Step 4: Name the reconstructed alkene. That structure is a methylcyclopentene with the double bond and methyl positioned as described in the matching option. Final answer: Option 3.
