2° Amines to N-Nitrosamines: Reaction with NaNO₂

Secondary amines—including alkyl and aryl—upon treatment with NaNO₂ and a strong acid yield secondary N-nitrosamines.

Recall that an acidified solution of NaNO₂ generates HNO₂. The unstable HNO₂ further undergoes protonation and subsequent dehydration to form the nitrosonium ion—an electrophile.

The nitrosyl cation, generated in situ, is attacked by the nucleophilic secondary amines to form an N-nitrosammonium ion.

The ion, upon deprotonation by solvent molecules, results in the formation of secondary N-nitrosamines.

Unlike primary N-nitrosamines—derived from primary amines—secondary N-nitrosamines are stable because the absence of the N–H proton prevents further tautomerism and eventual diazonium formation.

They usually separate as oily liquids from the reaction mixture.

In general, secondary N-nitrosamines have rare synthetic applications. However, many of them are known carcinogens found in processed food or tobacco.