Question

An organic compound (${\mathrm{C}}_3{\mathrm{H}}_9\mathrm{N}$) (A) when treated with Nitrous acid, gave an alcohol and ${\mathrm{N}}_2$ gas was evolved. (A) on warming with ${\mathrm{CHCl}}_3$ and Caustic potash gave (C), which on reduction gave isopropylmethylamine. Predict the structure of (A).

Answer 1

1. As the organic compound (${\mathrm{C}}_3{\mathrm{H}}_9\mathrm{N}$) (A) when treated with the Nitrous acid gives alcohol and also there's an evolution of ${\mathrm{N}}_2$ gas.
2. So, the compound should have to be the primary amine because only the primary amine on reaction with the Nitrous acid gives alcohol with the evolution of ${\mathrm{N}}_2$.
3. This Nitrous test is basically used for distinguishing between primary, secondary and tertiary amines.
4. Reaction: $\underset{\mathrm{Primary}\mathrm{amine}}{{\mathrm{RNH}}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Nitrous}\mathrm{acid}}{\mathrm{HONO}\left(\mathrm{aq}\right)}\to \underset{\mathrm{alcohol}}{\mathrm{ROH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}+\underset{\mathrm{Nitrogen}}{{\mathrm{N}}_2\left(\mathrm{g}\right)}$
5. Also according to the condition it gives isopropylmethyl amine in the carbylamine test so it should have to be the isopropyl amine and not the n-propyl amine.
6. Carbylamine reaction is basically used for the detection of the primary amines where the analyte is heated with the alcoholic Potassium hydroxide and Chloroform.
7. And so if a primary amine is present the isocyanide is formed, also this carbylamine test is not applicable for the secondary and tertiary amines.

Therefore, the structure for the the organic compound (A) would be:

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