Alcohols are the compounds containing hydroxyl group attached to the alkyl group, whereas phenols are hydroxyl derivatives of aromatic hydrocarbons in which hydroxyl group is directly attached to carbon atom of aromatic ring. Alcohols are versatile compounds and can behave both as nucleophiles as well as electrophiles.
Phenols, too are reactive compounds and are known to undergo reactions on : phenolic group, benzene ring as well as various other name reactions like Reimer-Tiemann reaction, Kolbe's reaction etc.
Which of the following is the correct structure of Aspirin?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 2-acetoxybenzoic acid (acetylsalicylic acid)
Phenols, like alcohols, react with acid chlorides and acid anhydrides to form esters. Bringing in an acetyl group (\( \ce{CH3CO} \)–) in place of the hydrogen of –OH is called acetylation. Salicylic acid (2-hydroxybenzoic acid) is acetylated at its phenolic –OH; the –COOH group stays free. The product, acetylsalicylic acid, is aspirin:
\( \ce{HOC6H4COOH + (CH3CO)2O} \xrightarrow{\ce{H+}} \ce{CH3COOC6H4COOH + CH3COOH} \)
So aspirin has an –OCOCH3 group and a –COOH group on adjacent ring carbons, as drawn in option (3).
Why the other options are incorrect
Option (1) 2-hydroxyacetophenone — Incorrect. It has a phenolic –OH and a ketone group (–\( \ce{COCH3} \)) on the ring; it has no ester and no –COOH group.
Option (2) phenyl salicylate — Incorrect. Here the –COOH of salicylic acid is esterified with phenol (–\( \ce{COOC6H5} \)) while the –OH stays free; this compound is salol, not aspirin.
Option (4) 1,2-phenylene diacetate — Incorrect. Both groups are acetoxy (–\( \ce{OCOCH3} \)); this is catechol with both –OH groups acetylated. It has no –COOH group, while aspirin is an acid (acetylsalicylic acid).
NCERT (2026-27 edition):
Esterification – “Alcohols and phenols react with carboxylic acids, acid chlorides and acid anhydrides to form esters. … The introduction of acetyl (CH3CO) group in alcohols or phenols is known as acetylation. Acetylation of salicylic acid produces aspirin.”