Question

(i) Which alkyl halide from the following pair is chiral and undergoes faster $S_{N}2$ reaction?
(ii) Out of $S_{N}1$ and $S_{N}2$, which reaction occurs with
(a) inversion of configuration?
(b) racemisation?

Answer 1

The secondary alkyl halide (option b) 2-bromobutane is chiral and undergoes faster $S_{N}1$ reaction. The chiral carbon atom is marked with asterik. The chiral carbon atom is carbon atom with four different atoms or groups of atoms.
The primary alkyl halide (option a) 1-bromobuane is achiral and undergoes faster $S_{N}2$ reaction.
$S_{N}2$ reaction gives inversion of configuration.
$S_{N}1$ reaction gives racemisation.