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

Concept: Lithium aluminium hydride (LiAlH$_4$) is a strong reducing agent that reduces:

• Nitriles (–C$\equiv$N) $\rightarrow$ Primary amines (–CH$_2$NH$_2$)

The carbon chain length remains the same during reduction.
Step 1: Identify the starting compound. Ethanenitrile = CH$_3$–C$\equiv$N It contains two carbon atoms.
Step 2: Apply reduction rule. Nitrile $\xrightarrow{\text{LiAlH}_4}$ Primary amine \[ \text{R–C}\equiv\text{N} \rightarrow \text{R–CH}_2\text{NH}_2 \]
Step 3: Write product. \[ \text{CH}_3\text{–C}\equiv\text{N} \rightarrow \text{CH}_3\text{–CH}_2\text{NH}_2 \] This is ethylamine.