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.