When a primary amine (aliphatic or aromatic) is heated with chloroform ($CHCl_3$) and ethanolic potassium hydroxide ($KOH$), it undergoes the Carbylamine reaction to form an isocyanide (or carbylamine). This product is characterized by a highly offensive or foul smell. This reaction serves as a specific qualitative test for primary amines, as secondary and tertiary amines do not undergo this reaction.

The general chemical equation is: $R-NH_2 + CHCl_3 + 3KOH \xrightarrow{\Delta} R-NC + 3KCl + 3H_2O$ Where $R-NC$ represents an alkyl (or aryl) isocyanide.