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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o3216

Which statements about epoxidation of alkenes with a peroxy acid are correct?

  1. AThe oxygen is delivered to one face of the double bond in one step, so the alkene geometry is retained in the ring
  2. B(E)-But-2-ene gives a racemic mixture of trans-2,3-dimethyloxirane enantiomers
  3. CCyclohexene gives trans-cyclohexane-1,2-diol directly in dry dichloromethane
  4. D(Z)-But-2-ene gives a single meso epoxide, cis-2,3-dimethyloxirane

Answer: A, B, D

The concerted syn transfer of oxygen keeps cis substituents cis, so (Z) gives the meso cis epoxide and (E) gives the trans epoxide. The trans epoxide is chiral and the two faces of the alkene are attacked equally, giving a racemate. A diol requires a second step (acid or base and water), so it does not form directly in dry solvent.
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