Exams › JEE Advanced › Chemistry
A solution of (-)-1-chloro-1-phenylethane in toluene slowly loses its optical activity (racemises) when a small amount of SbCl5 is added. This racemisation occurs because of the formation of a:
- carbanion
- carbene
- carbocation
- free radical
Correct answer: carbocation
Solution
SbCl5, a strong Lewis acid, abstracts the chloride ion from the benzylic carbon, generating a resonance-stabilized benzylic carbocation. This carbocation is planar (sp2), so re-addition of chloride can occur from either face, producing a racemic mixture and destroying optical activity.
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