Question

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

Answer 1

Alkyl halide also known by the name haloalkanes or halogenoalkanes which are generally those chemical compounds which are often derived from alkanes which contain one or more halogens. These are formed by the replacement of hydrogen atoms in an aliphatic hydrocarbon by any halogen atom.

Complete answer:
Nucleophiles generally take part in the nucleophilic substitution reactions and during this reaction nucleophile becomes attracted towards a partial or full positive charge rather than this neutral nucleophilic reactions with solvents like water is known by the name solvolysis. Nucleophilic substitution reaction is generally of two types known by the name $S{{N}_{1}}$and $S{{N}_{2}}$i.e. unimolecular nucleophilic substitution and bimolecular nucleophilic substitution.
The secondary alkyl halide given in the option b i.e. 2-bromobutane is chiral in nature and can undergo $S{{N}_{1}}$ reaction at faster rate. Chiral carbon atom is defined as that carbon atom which contains four different groups attached with itself.
Whereas in option 1 primary alkyl halide i.e. 1-bromobutane is given which is achiral in nature and this will undergo $S{{N}_{2}}$ reaction at faster rate.
Thus from this we can conclude that $S{{N}_{2}}$ reaction i.e. compound a gives inversion of configuration while $S{{N}_{1}}$ reaction i.e. compound b gives racemization.

Note:
Retention refers to that phase of the molecule in which the molecular composition is preserved throughout the reaction whereas inversion refers to that mechanism in which the structure of the molecules is changed during the reaction.