Read the passage carefully and answer the questions.
Amines are considered as derivatives of ammonia obtained by replacement of hydrogen atoms with alkyl or aryl groups. In nature they occur among proteins, vitamins, alkaloids and hormones. These can be primary, secondary or tertiary depending on the number of hydrogen groups replaced. They can be prepared from nitro compounds, alkyl halides, nitriles, amides etc. Due to unshared pair of electrons they behave as Lewis bases. Influence of the number of hydrogen atoms at nitrogen atom is displayed in physical properties such as solubility, boiling point and chemical reactions including basicity. Basic character of amines is expressed in terms of their \( K_b \) and \( pK_b \) values. Three classes of amines can be distinguished with p-toluene sulphonyl chloride which reacts with primary and secondary amines. Amino group when attached to benzene ring behaves as an activating and ortho para directing group.
Which reagent is used for the conversion of acetamide into ethylamine?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(LiAlH_4/H_2O\)
Amides are reduced to amines by lithium aluminium hydride. The C=O group of the amide is reduced to a –\( \ce{CH2} \)– group, so the amine has the same number of carbon atoms as the amide. The reduction is carried out in dry ether, and water is then added to hydrolyse the aluminium complex and set the amine free:
\( \displaystyle \ce{CH3CONH2} \xrightarrow[\text{(ii) }\ce{H2O}]{\text{(i) }\ce{LiAlH4}} \ce{CH3CH2NH2} \)
Acetamide (two carbon atoms) thus gives ethylamine (two carbon atoms). So the reagent is \( \ce{LiAlH4} \) followed by \( \ce{H2O} \).
Why the other options are incorrect
Option (1) \(H_2/Ni\) — Incorrect. Catalytic hydrogenation reduces nitro compounds and nitriles to amines (\( \ce{CH3CN} \) gives \( \ce{CH3CH2NH2} \)), but it does not reduce the amide C=O group under ordinary conditions.
Option (3) Na/Ethanol — Incorrect. Sodium and ethanol can reduce nitriles to primary amines, but they do not reduce amides.
Option (4) \(Br_2/NaOH\) — Incorrect. This is the Hofmann bromamide degradation: the alkyl group migrates from the carbonyl carbon to nitrogen and the carbonyl carbon is lost, so acetamide gives methylamine, an amine with one carbon atom less:
\( \displaystyle \ce{CH3CONH2 + Br2 + 4NaOH -> CH3NH2 + Na2CO3 + 2NaBr + 2H2O} \)
Note: In the original NTA paper, Option (4) was printed as “LiAlH4/ether”. This was also correct, because the reduction is carried out with LiAlH4 in dry ether and the amine is then set free by water, so Options (2) and (4) named the same LiAlH4 reduction system. Option (4) has been changed to “Br2/NaOH” so that students are not confused and the question has a single answer.
NCERT (2026-27 edition):
Reduction of Amides
