JEE Main 2025 Apr 7 Shift 1, Chemistry Q2: Analysis of Amines

Concept: The carbylamines (isocyanide) test is specific to primary amines only. When a primary amine is heated with chloroform and alcoholic KOH, a foul-smelling alkyl isocyanide is produced:

$\text{R}-{\text{NH}}_2+{\text{CHCl}}_3+3\text{KOH}\stackrel{\Delta }{\to }\text{R}-\text{NC}+3\text{KCl}+3{\text{H}}_2\text{O}$

Secondary and tertiary amines do not respond to this test.

Classifying the given amines:

A. Aniline $\Rightarrow$ 1${}^{\circ }$ amine $\Rightarrow$ positive

B. (CH${}_3$)${}_2$NH $\Rightarrow$ 2${}^{\circ }$ amine $\Rightarrow$ negative

C. CH${}_3$NH${}_2$ $\Rightarrow$ 1${}^{\circ }$ amine $\Rightarrow$ positive

D. (CH${}_3$)${}_3$N $\Rightarrow$ 3${}^{\circ }$ amine $\Rightarrow$ negative

E. N-methylaniline $\Rightarrow$ 2${}^{\circ }$ amine $\Rightarrow$ negative

$\therefore$ Only A and C give a positive carbylamines test $\Rightarrow$ Option (3).