Which of the following is chiral and gives racemic mixture on treatment with trace of base?
(A) (Et)(CH₃)(Ph)C-CO-CH₃ (B) 3-methylhexan-4-one (C) pentan-3-one (D) All of these

Question

Which of the following is chiral and gives racemic mixture on treatment with trace of base? (A) (Et)(CH 3 )(Ph)C-CO-CH 3 (B) 3-methylhexan-4-one (C) pentan-3-one (D) All of these

TestHub · Accepted Answer

Ans. (B).

Sol. Racemisation by a trace of base needs an enolisable alpha-H on the stereocentre, and the molecule must be chiral. (A) The stereocentre has no alpha-H, so it cannot racemise. (C) Pentan-3-one has no stereocentre, so it is not chiral. (B) 3-Methylhexan-4-one, CH₃CH₂-CH(CH₃)-CO-CH₂CH₃, is chiral and its stereocentre is alpha to C=O bearing an alpha-H, so base removes the alpha-H to give a planar enolate and the compound racemises.

Chemistry - STEREO ISOMERISM Question with Solution | TestHub

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