The high reactivity of alkyl halides can be explained in terms of nature of `C-X` bond which is a highly polarised covalent bond. This polarity is responsible for the nucleophilic substitution reaction of alkyl halides which jmostly occur by `S_(N^(1)) and S_(N^(2))` mechanisms. `S_(N^(1))` reaction is a two step process and in the first step `R-X` ionises to give carbocation (slow process). IN the second step, the nucleophile attacks the carbocation from either side to form the product (fast process). IN `S_(N^(1))` reaction, there can be racemization and inversion. `S_(N^(1))` reaction is favoured by heavy (bulky) group on the carbon atom attached to halogens. IN `S_(N^(2))` reaction, the strong nucleophile `OH^(-)` attacks fromt he opposite side Of the halogen atom to give an intermediate (transition state), which breaks to yields to product (alcohol) and leaving group `(X^(-))`. The alcohol has a configuratio opposite to that of the halide and is said to proceed with inversion of configuration. `S_(N^(2))` reaction is favoured by small groups on the carbon atom attached to halogen. Q. Which among the following will not give `S_(N^(1))` reaction?A. `CH_(3)-underset(C_(6)H_(5))underset(|)(C)H-Br`B. `(CH_(3))_(3)C-Br`C. `CH_(3)CH_(2)-I`D. `(C_(6)H_(5))_(2)underset(CH_(3))underset(|)(C)-Cl`.