QAIPM-2012-Ch-1633: NEET 2012 Chemistry - Class 12 AIPM-2012-Ch-1633 Solution: An organic compound when treated with nitrous acid gave an…

Step-by-Step Chemistry Walkthrough 1. Determine the category of Amine $\text{(A)}$: When an organic compound with the molecular formula $\mathrm{C}_{\mathrm{3}}\mathrm{H}_{\mathrm{9}}\mathrm{N}$ is treated with nitrous acid ($\mathrm{HNO}_{\mathrm{2}}$), it yields an alcohol and liberates nitrogen gas ($\mathrm{N}_{\mathrm{2}}$). � This specific reaction is a definitive property of primary aliphatic amines ($\mathrm{1}^{\mathrm{\circ }}$ amines). Therefore, $\text{(A)}$ must be a primary amine ($\mathrm{-NH}_{\mathrm{2}}$). 2. Analyze the Carbylamine Reaction: Primary amines, when warmed with chloroform ($\mathrm{CHCl}_{\mathrm{3}}$) and caustic potash ($\mathrm{KOH}$), undergo the carbylamine reaction to form foul-smelling alkyl isocyanides ($\mathrm{-NC}$): $\text{(A)}\xrightarrow{\mathrm{CHCl}_{\mathrm{3}}\mathrm{\ +\ KOH}}\text{(C)}\ (\text{Alkyl\ Isocyanide})$ 3. Deduced from the final reduction product: We are given that the reduction of compound $\text{(C)}$ gives isopropylmethylamine: $\mathrm{CH}_{\mathrm{3}}\mathrm{-}\overset{{}CH_{3}}{\underset{|}{CH}}\mathrm{-NH-CH}_{\mathrm{3}}$ � When an alkyl isocyanide ($\mathrm{R-NC}$) undergoes reduction (using $\mathrm{LiAlH}_{\mathrm{4}}$ or $\mathrm{H}_{\mathrm{2}}\mathrm{/Pd}$), it converts into a secondary methylamine ($\mathrm{R-NH-CH}_{\mathrm{3}}$). � Working backwards, since the final compound contains an isopropyl group attached to a methyl-substituted nitrogen, the isocyanide $\text{(C)}$ must be isopropyl isocyanide: $\mathrm{(CH}_{\mathrm{3}}\mathrm{)}_{\mathrm{2}}\mathrm{CH-NC}$ � Consequently, the initial primary amine $\text{(A)}$ that was subjected to the carbylamine test must be isopropylamine: $\mathrm{(CH}_{\mathrm{3}}\mathrm{)}_{\mathrm{2}}\mathrm{CH-NH}_{\mathrm{2}}$