Give reasons for the following
(a) Acetylation of aniline reduces its activation effect.
(b) `CH_(3)NH_(2)` is more basiic than `C_(6)H_(5)NH_(2)`.
(c) Although `-NH_(2)` is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline.

Explanation

(i) The acetyl group being electron-withdrawing attracts the lone pair of electrons on the N-atom towards itself. As a result, the activation effect of amino group is reduced.

(ii) Due to resonance, the lone pair of electrons on the nitrogen in aniline get delocalizes over the benzene ring and thus, is less easily available for protionation. Hence, aniline is weaker base than methyl amine

(iii) Under strongly acidic conditions of nitration, most of the aniline is converted into anilinium ion and `-Noverset(o+)(H)_(3)` is a meta directing group, therefore, an unexpected large amount of m-nitro aniline is obtained