Nitriitti

Nitrite, or nitrite ion NO2−, is the conjugate base of nitrous acid HNO2. In water it exists mainly as NO2− and forms salts such as sodium nitrite NaNO2 and potassium nitrite KNO2. It is widely used in food processing as a curing agent and color stabilizer, especially in processed meats, and is commonly referenced by the E-numbers E249 and E250.

Chemically, nitrite is a weak base. Its conjugate acid is nitrous acid HNO2, which is unstable in aqueous solution and can decompose to nitric oxide NO and other nitrogen oxides under certain conditions. In redox chemistry, nitrite can be oxidized to nitrate NO3− or reduced to nitric oxide NO, depending on the environment.

Biologically and environmentally, nitrite is an intermediate in the nitrogen cycle. Nitrifying bacteria oxidize ammonia to nitrite, and nitrite can be further oxidized to nitrate by nitrite-oxidizing bacteria. Under reducing conditions, some organisms convert nitrate to nitrite.

Beyond food, nitrite solutions are used in organic synthesis. In situ generation of nitrous acid from nitrite enables nitrosation reactions, such as the formation of diazonium salts from primary amines, which are important in synthetic chemistry.

Safety and regulation: high nitrite intake can cause methemoglobinemia, particularly in infants. Nitrite can react with amines to form N-nitrosamines, which are suspected carcinogens. Food-grade nitrites are regulated, and environmental nitrite from agricultural runoff and wastewater is monitored due to ecological effects.