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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3hx053

(S)-2-Bromobutane reacts with different nucleophiles by a pure $S_{N} 2$ pathway. Which statements are correct?

AAll three products below have the (S) configuration.
BWith $NaI$ in acetone the product is (R)-2-iodobutane.
CWith aqueous $OH X^{-}$ the product is (R)-butan-2-ol.
DWith $KCN$ in DMSO the product is (R)-2-methylbutanenitrile.

Answer: B, C, D

Each

S_{N} 2

inverts the spatial arrangement. In every product the nucleophile (

I

,

OH

or

CN

) outranks

C X_{2} H X_{5}

, which outranks

CH X_{3}

and

H

, the same order as with

Br

. The label therefore changes from S to R in all three products, so statement (a) is wrong.

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