Read the passage carefully and answer the Questions.
Amines are classified as primary (1°), secondary (2°) and tertiary (3°) depending upon the number of hydrogen atoms replaced by alkyl or aryl groups in ammonia molecules. Aliphatic amines are a stronger bases due to +I effect of an alkyl groups. Intermolecular hydrogen bonding in primary and secondary amines affects the boiling points of amines. The intermolecular association is more in primary amines than in secondary amines as there are more number of hydrogen atoms available for hydrogen bond formation. Nitro compounds are reduced to amines by passing hydrogen gas in the presence of finely divided nickel, palladium or platinum and also by reduction with metals in an acidic medium. Gabriel synthesis is used for the preparation of primary amines. Primary amines react with nitrous acid to give unstable diazonium-salts which can be used to synthesize a variety of compounds.
X in the following reaction is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → nitrobenzene
Nitro compounds are reduced to primary amines by catalytic hydrogenation: hydrogen gas is passed over finely divided nickel, palladium or platinum, here in ethanol as solvent. Each nitro group takes up three molecules of hydrogen and loses its two oxygen atoms as water:
\( \displaystyle \ce{C6H5NO2 + 3H2} \xrightarrow[\text{ethanol}]{\ce{H2}/\ce{Pd}} \ce{C6H5NH2 + 2H2O} \)
The product, aniline, has the same carbon skeleton as the starting compound, with \( \ce{-NH2} \) in place of \( \ce{-NO2} \). So X is nitrobenzene.
Why the other options are incorrect
Option (2) benzoic acid — Incorrect. The carboxyl carbon would have to be removed to give aniline; \( \ce{H2}/\ce{Pd} \) does not do this, and it does not even reduce the carboxyl group.
Option (3) benzamide — Incorrect. Benzamide gives aniline only by the Hofmann bromamide reaction (\( \ce{Br2} \) and NaOH), which removes the carbonyl carbon; reduction with \( \ce{LiAlH4} \) gives benzylamine instead.
Option (4) benzylamine — Incorrect. It is already an amine, \( \ce{C6H5CH2NH2} \); hydrogenation cannot remove its \( \ce{CH2} \) group to give aniline.
NCERT (2026-27 edition):
Reduction of Nitro Compounds
