Write a Short Note on Liebermann’s Nitroso Test

Answer:

• This test is used to distinguish between 1°, 2°, 3° amines
• Reagent used for this test is nitrous acid (HNO₂), a source of nitrosonium ion (NO+), to react with amines
• Because Nitrous acid is highly unstable, it is preferred to always freshly prepare it before use to get good results

                             NaNO₂+ HCl → HONO + NaCl

• For primary amines, reaction with nitrous acid results to form aliphatic Diazonium salt It is very unstable and decomposes rapidly to give out alcohol with release of nitrogen gas
• For 2° aliphatic amines or aromatic amines, the reaction with nitrous acid is slow and in cold conditions
• It produces a yellow oily product called nitroso amines 
• (C₂H₅)₂NH + HONO→ (C₂H₅)₂N−N=O + H₂O

                            (yellow oil)