Consider the following statements about the preparation of amines.
(A) Reduction of nitriles with lithium aluminium hydride is used for the ascent of the amine series.
(B) In the reduction of nitro compounds, iron scrap and hydrochloric acid are preferred because the FeCl2 formed is hydrolysed to release hydrochloric acid during the reaction.
(C) In the ammonolysis of an alkyl halide, a tertiary amine is obtained as the major product by taking a large excess of ammonia.
(D) Aromatic primary amines can be prepared by Gabriel phthalimide synthesis.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (B) only
(A) Reduction of nitriles with lithium aluminium hydride is used for the ascent of the amine series. — True. The carbon of –C≡N becomes –CH2NH2, so the amine formed has one carbon atom more:
\( \displaystyle \ce{R-C#N} \xrightarrow{\ce{LiAlH4}} \ce{R-CH2-NH2} \)
(B) In the reduction of nitro compounds, iron scrap and hydrochloric acid are preferred because the FeCl2 formed is hydrolysed to release hydrochloric acid during the reaction. — True. The acid is given back during the reaction, so only a small amount of HCl is needed to start it.
(C) In the ammonolysis of an alkyl halide, a tertiary amine is obtained as the major product by taking a large excess of ammonia. — False. Ammonolysis gives a mixture of amines, and a large excess of ammonia makes the primary amine the major product, not the tertiary amine.
(D) Aromatic primary amines can be prepared by Gabriel phthalimide synthesis. — False. Aromatic primary amines cannot be made this way, because aryl halides do not undergo nucleophilic substitution with the phthalimide anion.
NCERT (2026-27 edition):
9.4 Preparation of Amines – “Nitriles on reduction with lithium aluminium hydride (LiAlH4) or catalytic hydrogenation produce primary amines. This reaction is used for ascent of amine series, i.e., for preparation of amines containing one carbon atom more than the starting amine.”
“Reduction with iron scrap and hydrochloric acid is preferred because FeCl2 formed gets hydrolysed to release hydrochloric acid during the reaction. Thus, only a small amount of hydrochloric acid is required to initiate the reaction.”
“Ammonolysis has the disadvantage of yielding a mixture of primary, secondary and tertiary amines and also a quaternary ammonium salt. However, primary amine is obtained as a major product by taking large excess of ammonia.”
“…Aromatic primary amines cannot be prepared by this method because aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide.”