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JEE Main levelSingle correct optionDifficulty 2 of 3o3196

(Z)-But-2-ene is treated with $m - CPBA$ in dichloromethane. The product is

Acis-2,3-dimethyloxirane, a single achiral meso compound $(2 R, 3 S)$
Bracemic trans-2,3-dimethyloxirane, i.e. $(2 R, 3 R)$ and $(2 S, 3 S)$
Conly $(2 R, 3 R)$ -2,3-dimethyloxirane
Dmeso-butane-2,3-diol

Answer: A

Epoxidation with a peroxy acid is a syn addition of oxygen, so the geometry of the alkene is retained: the two methyl groups of the (Z)-alkene stay cis on the ring. cis-2,3-Dimethyloxirane has a mirror plane and is

(2 R, 3 S)

, i.e. meso. The diol does not form in the absence of water and acid.

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