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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o2231

The alkene shown undergoes hydroboration-oxidation ((i) in THF; (ii) , ). Select all correct statements about the product.

  1. AThe product is the trans-2-methyl alcohol (methyl and OH on opposite faces).
  2. BThe product is formed as a racemic mixture of two enantiomers.
  3. CThe OH group is attached to the ring carbon that bears the methyl group.
  4. DH and OH are delivered to the same face of the double bond (syn addition).

Answer: A, B, D

The alkene is 1-methylcyclopentene. Boron goes to the unsubstituted carbon and H to the carbon bearing the methyl, from the same face, so OH ends up on the CH carbon (not on the tertiary carbon) and is trans to the methyl. The achiral alkene is attacked equally from both faces, so the trans alcohol (1R,2R and 1S,2S) forms as a racemate. Statement C is therefore false.
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