–NO2, known as the nitro group, is a functional group in organic chemistry consisting of one nitrogen atom bonded to two oxygen atoms. It is commonly found in various compounds, including explosives like TNT and in some pharmaceuticals. The presence of the nitro group can significantly influence the chemical properties and reactivity of a molecule. In addition to its role in organic compounds, –NO2 is also important in environmental chemistry. It can be produced from combustion processes and is a component of nitrogen oxides (NOx), which contribute to air pollution and the formation of smog. Understanding –NO2 is crucial for both industrial applications and environmental protection.