Nucleophilic substitution reactions are of two types, substitution nucleophllic bimolecular `(SN^2)` and substitution nucleophilic unimolecular `(SN^1)` depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards `SN^1` and `SN^2` reactions depends on various factors such as steric hindrance, stability of intermediate or transition state and polarity of solvent. `SN^2` reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of `SN^1` reactions.
Among the choices of alkylbromide, the least reactive bromide in a `SN^2` reaction is

Options

A. 1-Bromopentane
B. 2-Bromo-2-methylbutane
C. 1-Bromo-3-methylbutane
D. All of the above

Answer

B