Reduction of amide with $\text{LiAlH}_4$ forming nitrile
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The Correct Option isB
Solution and Explanation
(1) Gabriel Phthalimide Synthesis prepares aliphatic primary amines. It fails for aniline because aryl halides do not undergo nucleophilic substitution with the phthalimide anion. Incorrect.
(2) Hoffmann Bromamide Degradation: $\text{R-CONH}_2 + \text{Br}_2 + 4\text{KOH} \to \text{R-NH}_2 + 2\text{KBr} + \text{K}_2\text{CO}_3 + 2\text{H}_2\text{O}$.
Here $\text{R} = \text{CH}_3\text{CH}_2$. Product is $\text{CH}_3\text{CH}_2\text{NH}_2$ (Ethylamine). This is correct.
(3) Carbylamine reaction forms Isocyanides ($\text{R-NC}$), characterized by a foul smell. Incorrect.
(4) Reduction of amides ($\text{RCONH}_2$) with $\text{LiAlH}_4$ yields Primary Amines ($\text{RCH}_2\text{NH}_2$). Dehydration with $\text{P}_2\text{O}_5$ would yield nitriles. Incorrect.