p-Hydroxyazobenzene is also known as
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Orange dye
Benzenediazonium chloride couples with phenol at its para position in alkaline solution to give p-hydroxyazobenzene. Its extended conjugated system (two benzene rings joined by –N=N–) absorbs in the visible region, so the compound is coloured: it is an orange dye. The similar product with aniline, p-aminoazobenzene, is a yellow dye.
\( \ce{C6H5N2+Cl- + C6H5OH} \xrightarrow{\ce{OH-}} \underset{\text{p-hydroxyazobenzene}}{\ce{HOC6H4N=NC6H5}} + \ce{Cl- + H2O} \)
NCERT (2026-27 edition):
Reactions Involving Retention of Diazo Group
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 02-06 S3 31-05 S1 | – |