JEE Main Chemistry Question (2026) — Solution

Step-by-step solution

The stability of benzenediazonium salts is governed by the electronic effects of the substituents present on the benzene ring. The diazonium group -N_2^+ is strongly electron-withdrawing. Electron-donating groups (EDG) stabilize the diazonium cation by dispersing the positive charge through resonance or inductive effects, whereas electron-withdrawing groups (EWG) destabilize it by increasing the positive charge density. In (A), the -OCH_3 group at the para position is a strong electron-donating group via the +M effect, which significantly stabilizes the diazonium ion. In (C), there is no substituent (hydrogen), providing a baseline stability. In (D), the -CN group is an electron-withdrawing group via -M and -I effects, which destabilizes the cation. In (B), the -NO_2 group is a very strong electron-withdrawing group via -M and -I effects, even stronger than -CN, leading to the least stability. Comparing the effects: +M of -OCH_3 (A) > H (C) > -M of -CN (D) > -M of -NO_2 (B). Therefore, the correct stability order is A > C > D > B.