Why are arenediazonium salts stable for a short time in solution at low temperatures?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → It is due to the resonance.
The extra stability of the arenediazonium ion comes from resonance: the π electrons of the benzene ring overlap with the –\( \ce{N^{+}} \)≡N group, so the positive charge is delocalised over the ring (at the ortho and para carbons). An alkyl group cannot delocalise the charge in this way.
So arenediazonium salts are stable at low temperature due to resonance.
Why the other options are incorrect
Option (1) It is due to the +I effect of azo group — Incorrect. The diazonium group (–\( \ce{N2^{+}} \)) is strongly electron withdrawing; it does not release electrons.
Option (2) It is due to the -I effect of phenyl ring — Incorrect. The phenyl ring stabilises the ion by resonance (electron donation into –\( \ce{N2^{+}} \)), not by an inductive pull; an electron-withdrawing effect would destabilise the cation.
Option (4) It is due to strong +R effect of azo group — Incorrect. The stabilisation comes from the ring donating electron density to the positively charged diazonium group, not from the diazonium group donating electrons.
NCERT (2026-27 edition):
Reaction with Nitrous Acid – …
