When (see structure) undergoes intramolecular aldol condensation, the major product formed is:
(A)(see structure)✓ Correct
(B)(see structure)
(C)(see structure)
(D)(see structure)
Answer: (A)
Solution
The substrate is 6-oxoheptanal, CH3CO−CH2CH2CH2CH2−CHO, bearing both a methyl ketone and an aldehyde. Base removes a proton from the carbon alpha to the ketone, and the resulting enolate adds to the more electrophilic aldehyde carbon. Because this closure forms a strain-free five-membered ring, it is strongly preferred, giving a cyclopentane ring that carries an acetyl group with a hydroxyl on the neighbouring carbon. Heating drives off water to set up conjugation with the acetyl carbonyl, so the major product is 1-acetylcyclopent-1-ene, a cyclopentene ring with the acetyl group on the double-bonded carbon.
JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Single correct option
