MHTCET 18 Apr 2026 Shift 2 Paper

Concept:The carbylamine reaction is given only by primary amines, producing isocyanides with a foul smell.Explanation:When a primary amine is heated with chloroform and ethanolic KOH, it forms an isocyanide. This compound has a very unpleasant, foul smell. The general reaction is: $$\mathrm{RNH}_{2} + \mathrm{CHCl}_{3} + 3\mathrm{KOH} \rightarrow \mathrm{RNC} + 3\mathrm{KCl} + 3\mathrm{H}_{2}\mathrm{O}$$ Here, $\mathrm{RNC}$ is the foul-smelling isocyanide. Now check each option: Benzenamine is aniline, $\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{NH}_{2}$, a primary aromatic amine, so it gives the foul smell. $N,N$-Dimethylaniline is a tertiary amine. It has no $-\mathrm{NH}_{2}$ group, so it does not undergo the carbylamine reaction. Thus, it does not produce a foul smell. Propan-2-amine is a primary aliphatic amine, so it gives the foul smell. Phenylmethanamine is benzylamine, $\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{CH}_{2}\mathrm{NH}_{2}$, a primary amine, so it gives the foul smell.Answer:The amine that does NOT produce a foul smell is $N,N$-Dimethylaniline, i.e., Option B.