Give reasons for the following
(a) Acetylation of aniline reduces its activation effect.
(b) `CH_(3)NH_(2)` is more basic 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) Due to the reasonance , the electron pair of nitrogenatom gets delocalised towards carbonyl group/resonating structures.
(ii) Because of `+ I` effect in methylamine electron density at nitrogen increases whereas in aniline resonance takes place and electron density on nitrogen decreases/ resonating structures.
(iii) Due to protonation of aniline/ formation of anilinium ion.