JEE Main 2026 — Apr 2, Shift 1 — Chemistry solution

JEE Main2026Apr 2, Shift 1Chemistry

Consider the three aromatic molecules (P, Q and R) whose structures have been given below :

The correct order regarding the reactivity of these compounds with

under optimum but slightly acidic medium is :

A
P > Q > R
B
R > P > Q
C
R > Q > P
D
P > R > Q

Solution

Diazonium coupling is an electrophilic aromatic substitution that requires the nitrogen lone pair on the $- N (C H_{3})_{2}$ group to be in conjugation with the ring (so that the para position is highly activated).

In P (unhindered N,N-dimethylaniline) the $- N (C H_{3})_{2}$ group lies in the plane of the ring; full $+ M$ donation is possible, so coupling is fast.

In Q, a single ortho-methyl group sterically twists the $- N (C H_{3})_{2}$ slightly out of the plane, reducing resonance donation.

In R, two ortho-methyls force the dimethylamino group nearly perpendicular to the ring (steric inhibition of resonance), almost shutting off the $+ M$ effect.

Therefore reactivity follows P > Q > R.

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