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.
Benzoic acid in the presence of conc. \( HNO_3 \) and conc. \( H_2SO_4 \) give major product as
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Meta-Nitrobenzoic acid
A group already on a benzene ring decides where a new electrophile enters. The –COOH group withdraws electrons from the ring by resonance and induction, so it is a deactivating and meta-directing group. Its resonance structures place a positive charge on the ortho and para carbons; the meta carbons are the least electron-poor, so the electrophile attacks there.
In the nitrating mixture, sulphuric acid generates the nitronium ion, \( \ce{NO2+} \), which substitutes at the meta position:
\( \displaystyle \ce{C6H5COOH + HNO3} \xrightarrow{\text{conc. }\ce{H2SO4}} m\text{-}\ce{O2NC6H4COOH + H2O} \)
So the major product is m-nitrobenzoic acid (3-nitrobenzoic acid).
Why the other options are incorrect
Option (1) Ortho-NitroBenzoic acid — Incorrect. The ortho positions carry a partial positive charge in the resonance structures of benzoic acid, so they repel the electrophile.
Option (2) Para-Nitrobenzoic acid — Incorrect. The para position is deactivated in the same way as the ortho positions.
Option (3) Mixture of Ortho and para-Nitrobenzoic acid — Incorrect. An ortho/para mixture is typical of activating groups such as –OH, –\( \ce{OCH3} \) or –\( \ce{CH3} \), and of halogens; –COOH is a meta director.
NCERT (2026-27 edition):
Ring Substitution
