Which of the following is correct about the esterification of an alcohol with a carboxylic acid?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → It is reversible, and therefore water is removed as soon as it is formed.
An alcohol and a carboxylic acid react to give an ester and water. A small amount of concentrated sulphuric acid is added, and because the reaction is reversible, the water is removed as soon as it forms so that the equilibrium shifts towards the ester:
\( \displaystyle \ce{R'COOH + ROH <=>[conc. H2SO4] R'COOR + H2O} \)
Why the other options are incorrect
Option (2) It is carried out in the presence of pyridine, which neutralises the HCl formed in the reaction. — Incorrect. Pyridine is used when the ester is made from an acid chloride, which gives HCl. A carboxylic acid gives water, not HCl.
Option (3) It needs a large amount of concentrated sulphuric acid, which is used up in the reaction. — Incorrect. Only a small amount of the acid is needed; it does not appear in the products.
Option (4) It takes place with alcohols but not with phenols. — Incorrect. Both alcohols and phenols form esters with carboxylic acids, acid chlorides and acid anhydrides.
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.” … “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.”