RNH2 + CHCl3 + 3KOH -> RNC (alkyl isocyanide) + 3KCl + 3H2O. Only primary amines (aliphatic and aromatic) give this test. The isocyanide (RNC) has a very foul, penetrating odour — the test is positive if this smell is detected. Secondary and tertiary amines do not react. This test is highly specific but unpleasant to perform. Note: CHCl3 + KOH first generates dichlorocarbene (:CCl2), which is the reactive intermediate. Do not confuse with Reimer-Tiemann (which also uses CHCl3/KOH but acts on phenol, not amines).