Which compound in each of the following pairs will react faster in `S_(N)2` reaction with `""^(Θ)OH` ?
(i) `CH_(3)Br` or `CH_(3)I`
(ii) `(CH_(3))_(3)C Cl` or `CH_(3)Cl`

Explanation

(i) Due to large size of iodine, the C - I bond is a weak bond as compared to C - Br. Also, `I^(-)` is a better leaving group. So, `CH_(3) - I` will react with `""^(Θ)OH` via `S_(N)2` than `CH_(3)-Br`.

(ii) In `S_(N)2` reaction, the nucleophile attacks from the opposite side of the leaving group. The attack is favoured if there is presence of small groups i.e., minimum steric hindrance. Thus, `CH_(3)Cl` will react faster via `S_(N)2`.