Consider the following statements about the esterification of alcohols and phenols.
(A) The reaction of an alcohol with a carboxylic acid to form an ester is carried out in the presence of a small amount of concentrated sulphuric acid.
(B) The esterification of an alcohol with a carboxylic acid is reversible, and therefore, water is removed as soon as it is formed.
(C) The reaction of an alcohol with an acid chloride is carried out in the presence of pyridine so as to neutralise the water formed during the reaction.
(D) Aspirin is produced by the acetylation of phenol.
Which of the statements given above are incorrect? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (C) and (D) only
Alcohols and phenols form esters with carboxylic acids, acid chlorides and acid anhydrides. The conditions of each reaction depend on the by-product it gives: water with an acid, HCl with an acid chloride.
(A) The reaction of an alcohol with a carboxylic acid to form an ester is carried out in the presence of a small amount of concentrated sulphuric acid. — Correct statement. A little concentrated H2SO4 is used with a carboxylic acid or an acid anhydride.
(B) The esterification of an alcohol with a carboxylic acid is reversible, and therefore, water is removed as soon as it is formed. — Correct statement. Removing water keeps the reversible reaction moving towards the ester.
\( \displaystyle \ce{CH3COOH + C2H5OH} \overset{\ce{H+}}{\rightleftharpoons} \ce{CH3COOC2H5 + H2O} \)
(C) The reaction of an alcohol with an acid chloride is carried out in the presence of pyridine so as to neutralise the water formed during the reaction. — Incorrect statement. An acid chloride gives HCl, not water, as the by-product. Pyridine, a base, neutralises this HCl and shifts the equilibrium to the right.
\( \displaystyle \ce{R/ArOH + R'COCl} \xrightarrow{\text{Pyridine}} \ce{R/ArOCOR' + HCl} \)
(D) Aspirin is produced by the acetylation of phenol. — Incorrect statement. Aspirin is produced by the acetylation of salicylic acid (2-hydroxybenzoic acid). Acetylation of phenol gives an ester of phenol that has no –COOH group.
NCERT (2026-27 edition):
7.4.4 Chemical Reactions – “2. Esterification … Alcohols and phenols react with carboxylic acids, acid chlorides and acid anhydrides to form esters.”
\( \displaystyle \ce{R/ArOH + R'COCl} \xrightarrow{\text{Pyridine}} \ce{R/ArOCOR' + HCl} \)
“The reaction with carboxylic acid and acid anhydride is carried out in the presence of a small amount of concentrated sulphuric acid. The reaction is reversible, and therefore, water is removed as soon as it is formed. The reaction with acid chloride is carried out in the presence of a base (pyridine) so as to neutralise HCl which is formed during the reaction. It shifts the equilibrium to the right hand side. The introduction of acetyl (CH3CO) group in alcohols or phenols is known as acetylation. Acetylation of salicylic acid produces aspirin.”