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JEE Advanced levelSingle correct optionDifficulty 3 of 3hx220

(3R,4S)-3-Chloro-3,4-dimethylhexane undergoes hydrolysis in water by a pure SN1 mechanism (planar carbocation at C-3; C-4 is unaffected). The 3,4-dimethylhexan-3-ol products are

  1. Aall four stereoisomers in equal amounts
  2. Bonly (3S,4S), because of inversion
  3. C(3R,4S) and (3S,4R), which are enantiomers; the mixture is racemic and inactive
  4. D(3R,4S) and (3S,4S), which are diastereomers; the mixture is optically active

Answer: D

The planar cation loses the configuration at C-3 only; C-4 stays S. Attack on either face gives (3R,4S) and (3S,4S). These are diastereomers, not mirror images, so they need not form in equal amounts and the mixture is generally optically active.
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