Aldol condensation is a popular and classical method to prepare α,β-unsaturated carbonyl compounds. This reaction can be both intermolecular and intramolecular. Predict which one of the following is not a product of intramolecular aldol condensation?
(A)(see structure)
(B)(see structure)
(C)(see structure)
(D)(see structure)✓ Correct
Answer: (D)
Solution
An intramolecular aldol condensation needs a dicarbonyl in which an enolate carbon can reach an internal carbonyl, and the dehydration that follows sets the new double bond in conjugation with the surviving carbonyl, giving an endocyclic α,β-unsaturated ketone. The fused octalone, the indanone-derived enone and cyclohex-2-en-1-one all fit this pattern. A ring ketone bearing an exocyclic =CH2 at the α-carbon would require condensation with a one-carbon formaldehyde unit and cannot arise from folding a single dicarbonyl onto itself, so the α-methylene ring ketone is the structure that is not a product of intramolecular aldol condensation.
JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Single correct option
