NEET 2023 Phase 1 · ChemistryHofmann degradationPrevious Year Question

Which of the following reactions will NOT give a primary amine as the product?

Answer: (C) (C) $CH X_{3} NC (i) LiAlH X_{4} (ii) H X_{3} O X^{+} Product$ . \textbf{Answer:} (C) Reduction of an isocyanide (R-NC) gives a SECONDARY amine, not a primary amine.

A.(A) $CH X_{3} CONH X_{2} Br X_{2} / KOH Product$
B.(B) $CH X_{3} CN (i) LiAlH X_{4} (ii) H X_{3} O X^{+} Product$
C.(C) $CH X_{3} NC (i) LiAlH X_{4} (ii) H X_{3} O X^{+} Product$ ✓
D.(D) $CH X_{3} CONH X_{2} (i) LiAlH X_{4} (ii) H X_{3} O X^{+} Product$

Correct Answer

Solution & Explanation

\textbf{Answer:} (C) Reduction of an isocyanide (R-NC) gives a SECONDARY amine, not a primary amine. \textbf{Solution:} Reduction of methyl isocyanide gives an N-methyl secondary amine: $CH X_{3} NC LiAlH X_{4} CH X_{3} NHCH X_{3}$ (the N is bonded to two carbons). So (C) does NOT give a primary amine. The others all give primary amines: (A) Hoffmann bromamide: $CH X_{3} CONH X_{2} Br X_{2} / KOH CH X_{3} NH X_{2}$ (primary, one less carbon). (B) Nitrile reduction: $CH X_{3} CN LiAlH X_{4} CH X_{3} CH X_{2} NH X_{2}$ (primary). (D) Amide reduction: $CH X_{3} CONH X_{2} LiAlH X_{4} CH X_{3} CH X_{2} NH X_{2}$ (primary). Hence the correct choice is (C).

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