Question

The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is:

• A. Retention occurs in $SN_1$ reaction and inversion occurs in $SN_2$ reaction.
• B. Racemisation occurs in $SN_1$ reaction and retention occurs in $SN_2$ reaction.
• C. Racemisation occurs in both $SN_1$ and $SN_2$ reactions.
• D. Racemisation occurs in $S_N1$ reaction and inversion occurs in $S_N2$ reaction.

Answer 1

Answer: (D)

Racemisation occurs in $S_N1$ reaction and inversion occurs in $S_N2$ reaction.

Answer 2

- SN1 Reaction: This reaction proceeds via a carbocation intermediate, leading to a racemic mixture if the carbon is chiral, due to the planar nature of the carbocation.

- SN2 Reaction: This reaction involves a backside attack, resulting in inversion of configuration (Walden inversion) if the carbon is chiral.

Thus, racemisation occurs in SN1 reactions and inversion occurs in SN2 reactions.