NO2Ion

NO2Ion refers to the nitrite ion, NO2−, an anion derived from nitrous acid (HNO2). It occurs in aqueous solutions and in various salts, and it participates in acid–base and redox chemistry typical of nitrite species. As the conjugate base of nitrous acid, nitrite is important in the nitrogen cycle and in many industrial and environmental contexts.

Structure and bonding: The nitrite ion features two equivalent N–O bonds and a central nitrogen atom with one lone pair. Through resonance, the ion is described by forms such as O=N−O− and O−N=O−, giving bond orders between single and double and a delocalized negative charge over the oxygens. The molecular geometry around nitrogen is bent, with an approximate bond angle near 115 degrees. The overall charge of the ion is −1.

Formation and occurrence: In natural systems, nitrite arises from microbial reduction of nitrates and from partial oxidation processes in water and soils. It is also produced industrially and is present in nutrition and food contexts as salts (for example sodium nitrite) used in curing meats. In aqueous environments, nitrite levels reflect redox conditions and nitrogen-transforming processes.

Reactions and uses: Nitrite can act as a mild reducing agent and as an intermediate that can be oxidized to nitrate or reduced to nitric oxide (NO) under certain conditions, the latter being biologically significant as a signaling molecule. In food chemistry, nitrite can react with secondary amines to form nitrosamines, a class of compounds with safety considerations. In water treatment and chemistry, nitrite can interfere with disinfection processes and influence chemical equilibria.

Safety and regulation: Elevated nitrite concentrations can be toxic, notably causing methemoglobinemia in humans or animals. Regulatory limits exist for drinking water and food products to control exposure.