Give reasons for the following:
(a) Acetylation of aniline reduces its activating effect.
(b) CH₃NH₂ is more basic than C₆H₅NH₂.
(c) Although –NH₂ is an o/p-directing group, aniline on nitration gives a significant amount of m-nitroaniline.
(a) Acetylation of aniline reduces its activating effect.
(b) CH₃NH₂ is more basic than C₆H₅NH₂.
(c) Although –NH₂ is an o/p-directing group, aniline on nitration gives a significant amount of m-nitroaniline.
Solution
(a) In acetanilide the N lone pair conjugates with the carbonyl, so far less density reaches the ring — activation drops to mild.
(b) CH's +I enriches N and stabilises CHNH; aniline's lone pair is ring-shared and its cation loses that resonance.
(c) Nitration medium (HNO/HSO) protonates much of the aniline to CHNH — a deactivating, \textbf{meta-directing} group — so nearly half the product is m-nitroaniline alongside the o/p from free aniline.
(b) CH's +I enriches N and stabilises CHNH; aniline's lone pair is ring-shared and its cation loses that resonance.
(c) Nitration medium (HNO/HSO) protonates much of the aniline to CHNH — a deactivating, \textbf{meta-directing} group — so nearly half the product is m-nitroaniline alongside the o/p from free aniline.
CBSE Class 12 Board · 2017 · Subjective