MHTCET 13 Apr 2026 Shift 1 Paper

Concept:The carbylamine test is a distinctive reaction shown only by primary amines.Explanation:Acetylation and alkylation are shown by both primary and secondary amines, so options A and B are incorrect.Reaction with nitrous acid ($\mathrm{HNO_2}$) is given by all three classes of amines.Primary amines give alcohols, secondary amines give $N$-nitrosoamines, and tertiary amines give nitrite salts.Thus, option C is not exclusive to primary amines.In the carbylamine test, a primary amine is heated with chloroform ($\mathrm{CHCl_3}$) and alcoholic potassium hydroxide ($\mathrm{KOH}$).It forms an isocyanide ($\mathrm{RNC}$) having a very unpleasant smell.$$\mathrm{RNH_2} + \mathrm{CHCl_3} + 3\mathrm{KOH} \rightarrow \mathrm{RNC} + 3\mathrm{KCl} + 3\mathrm{H_2O}$$Secondary and tertiary amines do not give this test.Therefore, the carbylamine test is exhibited only by primary amines, both aliphatic and aromatic.Answer:D. carbyl amine test