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

Explanation

(i) Since `I^(-)` ion is a better leaving group than `Br^(-)` ion, therefore, `CH_(3)I` reacts faster than `CH_(3)` Br in `S_(N)2` reaction with `OH^(-)` ion.
(ii) On steric grounds, `1^(@)` alkyl halides are more reactive than tertalkyl halides in `S_(N)2` reactions. Therefore, `CH_(3)I`. will react at a faster rate than `(CH_(3))_(3) C Cl` in a `S_(N)2` reaction with `OH^(-)` ion.