Nitriles on reduction with lithium aluminum hydride produce

The correct answer is Option (2) → Primary amine

Lithium aluminium hydride is a strong reducing agent that supplies hydride ions (\( \ce{H^{-}} \)). It adds four hydrogen atoms across the C≡N triple bond: the carbon becomes a \( \ce{CH2} \) group and the nitrogen an \( \ce{NH2} \) group. The product is a primary amine:

    \( \displaystyle \ce{R-C#N} \xrightarrow[\text{(ii) }\ce{H2O}]{\text{(i) }\ce{LiAlH4}} \ce{R-CH2-NH2} \)

For example, ethanenitrile gives ethanamine: \( \ce{CH3CN -> CH3CH2NH2} \). Catalytic hydrogenation (\( \ce{H2} \)/Ni) does the same. Because the amine has one carbon more than the alkyl halide used to make the nitrile, the method is used for the ascent of the amine series.

Why the other options are incorrect

• Option (1) Amides — Incorrect. An amide is formed by the partial hydrolysis of a nitrile, which adds water, not hydrogen: \( \ce{RCN + H2O} \xrightarrow{\ce{H+}} \ce{RCONH2} \)

• Option (3) Ammonium salt — Incorrect. Complete hydrolysis of a nitrile with acid gives a carboxylic acid and an ammonium salt; reduction gives none:

      \( \displaystyle \ce{R-CN + 2H2O + HCl -> R-COOH + NH4Cl} \)

• Option (4) Secondary amine — Incorrect. The nitrogen of the nitrile is bonded to only one carbon, so reduction can give only a primary amine; a secondary amine needs a second alkyl group on nitrogen, for example by alkylation of a primary amine.

NCERT (2026-27 edition):
Reduction of Nitriles

Note: The same/similar question has been asked in different years by NTA as per the details given below: