Which of the following reactions will not give a primary amine?
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When reducing amides, nitriles, or using the Hofmann Bromamide reaction, primary amines are obtained. However, the reduction of isocyanides produces a secondary amine instead.
The reactions and their respective products are as follows:
(a) Hofmann Bromamide Reaction:
\[
\text{CH}_3\text{CONH}_2 \xrightarrow{\text{Br}_2/\text{KOH}} \text{CH}_3\text{NH}_2.
\]
This reaction involves the conversion of an amide (\( \text{CONH}_2 \)) to a primary amine (\( \text{CH}_3\text{NH}_2 \)) with the loss of one carbon atom.
(b) Reduction of Nitriles:
\[
\text{CH}_3\text{CN} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{CH}_2\text{NH}_2.
\]
Nitriles (\( \text{CN} \)) are reduced to primary amines (\( \text{CH}_3\text{CH}_2\text{NH}_2 \)) using lithium aluminium hydride (\( \text{LiAlH}_4 \)).
(c) Reduction of Isocyanides (Methyl Isocyanide):
\[
\text{CH}_3\text{NC} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{NHCH}_3.
\]
Isocyanides (\( \text{NC} \)) are reduced to secondary amines (\( \text{CH}_3\text{NHCH}_3 \)) using lithium aluminium hydride. Hence, this reaction does not produce a primary amine.
(d) Reduction of Amides:
\[
\text{CH}_3\text{CONH}_2 \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{CH}_2\text{NH}_2.
\]
Amides (\( \text{CONH}_2 \)) are reduced to primary amines (\( \text{CH}_3\text{CH}_2\text{NH}_2 \)) using lithium aluminium hydride.
Conclusion:
Among the given reactions, option (3) does not produce a primary amine; it produces a secondary amine instead.
Final Answer:
\[
\boxed{\text{CH}_3\text{NC} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{NHCH}_3 \text{ (Secondary Amine)}}.
\]
