Which of the following compounds lacks a phenolic group?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Glycerol
A phenolic group is an –OH group bonded directly to a carbon of a benzene ring (an sp2 carbon). An –OH group on an sp3 carbon of a chain is an alcoholic group.
Option (1) Catechol — Has a phenolic group. It is benzene-1,2-diol, with two –OH groups on the ring.
Option (2) Glycerol — Lacks a phenolic group. It is propane-1,2,3-triol, \( \ce{HOCH2-CH(OH)-CH2OH} \): no benzene ring, and its three –OH groups are on sp3 carbons, so it is a trihydric alcohol.
Option (3) Resorcinol — Has a phenolic group. It is benzene-1,3-diol.
Option (4) Hydroquinone — Has a phenolic group. It is benzene-1,4-diol (quinol).
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| 19-05 S2 | 22-05 S1 | – | – | – |