Read the passage carefully and answer the questions.
Alcohols and phenols are formed when a hydrogen atom in a hydrocarbon, aliphatic and aromatic respectively is replaced by - OH group. These are further classified on the basis of number of hydroxy groups and according to the hybridization of the carbon atom \( sp^2 \) or \( sp^3 \) to which the -OH group is attached. They find applications in industry as well as in day-to-day life. One of the most commercially obtained alcohol also known as wood spirit is obtained by destructive distillation of wood. Both alcohols and phenols are acidic in nature. The acidity of alcohols and phenols vary according to the nature of substituent(s) attached to them. Alcohols and phenols react with carboxylic acids, acid chlorides and acid anhydrides to form esters. Introduction of acetyl group in alcohols and phenols is called acetylation. Phenol undergo electrophilic aromatic substitution reaction because the -OH activates the benzene ring. It undergoes nitration, halogenation and sulphonation reactions.
Which of the following compound 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) Quinol — Has a phenolic group. It is benzene-1,4-diol (hydroquinone), 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) Cresol — Has a phenolic group. It is methylphenol, with one –OH group on the ring.
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 | – | – | – |