Aman has been asked to synthesise the molecule
He thought of preparing the molecule using an aldol condensation reaction. He found a few cyclic alkenes in his laboratory. He thought of performing ozonolysis reaction on alkene to produce a dicarbonyl compound followed by aldol reaction to prepare " x ". Predict the suitable alkene that can lead to the formation of " x ".

Solution

Chemistry ma’am · 4 steps

Work backwards: the acetyl group must come from a methyl ketone, so the alkene carbon must carry a methyl.

1. Read the target. In x the ring is a cyclopentene, and the ring double bond carries a -COCH₃ group. That is the classic product of an intramolecular aldol condensation of a 1,6-dicarbonyl compound, which closes a five-membered ring.
2. What ozonolysis must give. The acetyl group needs a methyl ketone at one end of the chain, and the aldol needs an aldehyde at the other end. So we want CH₃CO-CH₂CH₂CH₂CH₂-CHO (6-oxoheptanal). Ozonolysis of 1-methylcyclohexene gives exactly this: the ring carbon carrying CH₃ becomes the ketone and the other alkene carbon becomes CHO.

   CH₃CO-CH₂CH₂CH₂CH₂-CHO →(base, -H₂O) 1-acetylcyclopentene

3. The ring closure. Base removes an α-H from the CH₂ next to the ketone. This enolate attacks the aldehyde carbon five atoms away, forming a five-membered ring. Losing water puts the double bond between the two, with COCH₃ on the ring alkene carbon, which is x.

   Option	Alkene	Ozonolysis gives	Can it give x?
   (a)	4-methylcyclohexene	3-methylhexanedial (two CHO ends)	No: ring gets CHO, not COCH₃
   (b)	3-methylcyclohexene	2-methylhexanedial (two CHO ends)	No: ring gets CHO, not COCH₃
   (c)	methylenecyclohexane	cyclohexanone + HCHO	No: two separate molecules, no dicarbonyl
   (d)	1-methylcyclohexene	6-oxoheptanal (ketone + CHO)	Yes

4. So. Only 1-methylcyclohexene, option (d), gives the keto-aldehyde whose intramolecular aldol condensation forms x.

The idea to keep. For ozonolysis plus aldol questions, go backwards: find the 1,5- or 1,6-dicarbonyl, then join its two carbonyl carbons with a double bond to get the alkene. A COCH₃ group means a methyl on the alkene carbon.

Answer from the NTA final answer key. Solution by PrepWiser.