Predict the major product in the following reaction:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → p-Hydroxyazobenzene
Benzenediazonium chloride couples with phenol in mildly alkaline solution. The phenol molecule is attacked at its para position and an –N=N– (azo) bridge joins the two rings:
\( \displaystyle \ce{C6H5N2+Cl- + C6H5OH} \xrightarrow{\ce{OH-}} p\text{-}\ce{HO-C6H4-N=N-C6H5 + Cl- + H2O} \)
The product is p-hydroxyazobenzene, an orange dye.
Why the other options are incorrect
Option (1) p-Aminoazobenzene — Incorrect. p-aminoazobenzene (yellow dye) is formed when the diazonium salt couples with aniline, not phenol.
Option (3) Sulphanilic acid — Incorrect. Sulphanilic acid comes from sulphonation of aniline; it plays no part in this reaction.
Option (4) Phenol — Incorrect. Phenol is formed when a diazonium salt is warmed with water; here phenol is a reactant and the azo group is retained.
NCERT (2026-27 edition):
Reactions Involving Retention of Diazo Group
