NEET 2022, Chemistry Q42: Properties and Important Reactions of Aldehydes & Ketones
Which one of the following is not formed when acetone reacts with 2-pentanone in the presence of dilute NaOH followed by heating ?

- A
1
- B
2
- C
3
- D
4

Aldol condensation between acetone and 2-pentanone can proceed by self-condensation of each ketone (giving mesityl oxide from acetone and the 2-pentanone self-product) or by cross-condensation between the two.
In a cross aldol step, one carbonyl provides the -carbon (enolate) and the other acts as the electrophile. The two viable cross products are formed with the carbon skeletons predictable from this pairing.
The structure shown in option (1) corresponds to a coupling pattern that does not match any of the four feasible aldol products of this pair. Hence (1) is not formed.
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