Question

Identify the compound produced by the reduction of ethanenitrile with lithium aluminium hydride:

• A. Ethylamine
• B. Ethanal
• C. Propylamine
• D. Methylamine

Hint:

LiAlH$_4$ reduction rules: Nitrile $\rightarrow$ Primary amine Amide $\rightarrow$ Amine Carbon chain length remains unchanged.

Answer 1

The Correct Option is A

The reduction of ethanenitrile using lithium aluminium hydride (LiAlH₄) is a common method to produce primary amines. Here's a detailed explanation of the process:

1. Understanding the Reaction:
   • Ethanenitrile, also known as acetonitrile, has the chemical formula CH₃CN.
   • Lithium aluminium hydride (LiAlH₄) is a strong reducing agent used to reduce nitriles to primary amines.
2. Reaction Mechanism:
   • In the presence of LiAlH₄, the nitrile group (−C≡N) in ethanenitrile is reduced.
   • The reduction involves the addition of hydrogen atoms to the carbon (C) and nitrogen (N) atoms, converting the nitrile group into a primary amine (−NH₂).
   • The chemical reaction can be represented as:

\(\text{CH}_3\text{CN} + 4\text{[H]} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{CH}_2\text{NH}_2\)

1. End Product:
   • The product of the reduction is ethylamine (CH₃CH₂NH₂).
2. Justification of the Correct Answer:
   • Ethylamine is a primary amine with an ethyl group attached to the nitrogen, which matches the product obtained from the reduction of ethanenitrile.
   • Hence, the correct answer is "Ethylamine."
3. Ruling Out Other Options:
   • Ethanal: It is an aldehyde and cannot be produced through nitrile reduction using LiAlH₄.
   • Propylamine: This is incorrect as the carbon chain would need to be extended, which doesn’t happen in this reaction.
   • Methylamine: Would be the product if the nitrile had been a single carbon compound like HCN, not ethanenitrile.

Therefore, the compound produced by the reduction of ethanenitrile with lithium aluminium hydride is Ethylamine.