Amines

The arenium ion which is not involved in the bromination of Aniline is .

1. [figure]
2. [figure]
3. [figure]
4. [figure]

Answer

(4) [figure]

Solution

–NH2 is a strong o/p-director: in ortho / para attack the positive charge comes on the carbon bearing –NH2 and the N lone pair stabilises it (iminium form). In meta attack the + charge falls only on C-2, C-4, C-6 — never on C-1, so N cannot stabilise it.

(A): H, Br at C-4 (para), = NH2 form ⇒ (A) is involved

(B): H, Br at C-2 (ortho), + at C-3 ⇒ (B) is involved

(C): H, Br at C-2 (ortho), = NH2 form ⇒ (C) is involved

(D): H, Br at C-3 (meta) ⇒ (D) is not involved

∵ Aniline with bromine water gives 2,4,6-tribromoaniline (only o/p attack).

Answer: (4)