Nitrite can enter two kinds of reaction, depending on the physico-chemical environment. 
* Nitrosylation is adding a nitrosyl ion  to a metal (e.g. iron) or a thiol, leading to nitrosyl iron  (e.g., in nitrosylated heme = nitrosylheme) or S-nitrosothiols (RSNOs).
* Nitrosation is adding a nitrosonium ion  to an amine – leading to a nitrosamine. This conversion occurs at acidic pH, particularly in the stomach, as shown in the equation for the formation of N-phenylnitrosamine:
Many primary alkyl N-nitroso compounds, such as , tend to be unstable with respect to hydrolysis to the alcohol. Those derived from secondary amines (e.g.,  derived from dimethylamine) are more robust. It is these N-nitrosamines that are carcinogens in rodents.