Read the passage carefully and answer the questions.
Carboxylic acids are the organic compounds which comprise of carboxyl functional group, -COOH. These are generally found in nature, some higher members are known as fatty acids as they occur in natural fats as esters of glycerol. They can be prepared from oxidation of alcohols and aldehydes, hydrolysis of nitriles and amides and Grignard reagents. They are stronger acids than simple phenols and alcohols. but weaker than mineral acids. Substituents affect the acidity of aliphatic and aromatic carboxylic acids. They undergo reactions involving cleavage of -OH and C-OH bond. Carboxylic acids having an alpha hydrogen get halogenated in the presence of red phosphorus to form alpha halo carboxylic acids. The reaction is known as Hell Volhard Zelinsky reaction. Besides these aromatic carboxylic acids undergo electrophilic substitution reactions. They are versatile and are employed in the manufacture of various useful compounds. For example, methanoic acid is used in rubber, textile, dyeing, leather and electroplating industries. Higher fatty acids are used in the manufacture of soaps and detergents. Esters of Benzoic acid are used in perfumery.
Esterification of carboxylic acid with alcohols or phenols is which type of reaction?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Nucleophilic acyl substitution
In a nucleophilic acyl substitution, a nucleophile attacks the carbonyl carbon of an acyl group (RCO–) and replaces the group attached to it. The reaction goes through a tetrahedral intermediate: addition first, then loss of a leaving group, so the C=O group is regenerated.
In esterification the –OH of the acid is replaced by –OR′:
\( \displaystyle \ce{RCOOH + R'OH} \xrightarrow{\ce{H+}} \ce{RCOOR' + H2O} \)
Why the other options are incorrect
Option (1) Nucleophilic Substitution — Incorrect. This name is used for the SN1 and SN2 reactions of haloalkanes at an sp3 carbon. Esterification takes place at the sp2 carbonyl carbon through a tetrahedral intermediate, which is why it is called an acyl substitution.
Option (3) Nucleophilic addition — Incorrect. This is the reaction of aldehydes and ketones, where the added groups stay in the product. In esterification the addition is followed by the loss of water, so the net change is a substitution.
Option (4) Electrophilic addition — Incorrect. This is the typical reaction of alkenes and alkynes, where an electrophile adds to a C=C or C≡C bond.
NCERT (2026-27 edition):
Reactions Involving Cleavage of C–OH Bond – …
