KCET 2021 Chemistry Solved Paper

The order of reactivity of given compounds in SN2 reaction is For SN2 reaction, the order of reaction is inversely proportional to steric hinderance cause by bulky groups.
In (C6H5)2

C |

Br

−CH3(3° halide ), there are two bulky
groups are present i.e. benzene group and one methyl group which provide steric hinderance for the attack of nucleophile. Hence, it is least reactive while in C6H5CH2‌Br (1° halide), the attack of nucleophile is easier due to less steric hinderance.