Consider the three aromatic molecules (P, Q and R) whose structures have been given below:
P. (see structure)
Q. (see structure)
R. (see structure)
The correct order regarding the reactivity of these compounds with Ph−N≡NCl(−) under optimum but (+) slightly acidic medium is:PQR
(A)P > Q > R✓ Correct
(B)R>P>Q
(C)R>Q>P
(D)P > R > Q
Answer: (A)
Solution
Coupling with the benzenediazonium ion is an electrophilic substitution whose rate depends on how strongly the −N(CH3)2 lone pair can be fed into the ring. In P (N,N-dimethylaniline) the amino group lies coplanar with the ring and donates fully. In Q a single ortho methyl twists the −N(CH3)2 group partly out of the ring plane, weakening this donation by steric inhibition of resonance. In R two ortho methyls force the group almost perpendicular, nearly removing the donation. The reactivity therefore decreases in the order P > Q > R.
JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Single correct option
