R-NO2 refers to a class of organic compounds known as nitro compounds, where "R" represents an organic group, such as an alkyl or aryl group. The nitro group (–NO2) is a functional group that consists of one nitrogen atom bonded to two oxygen atoms, one of which is double-bonded. Nitro compounds are often used in the production of explosives, dyes, and pharmaceuticals due to their unique chemical properties. These compounds can be synthesized through various chemical reactions, including the nitration of organic substrates. Nitro compounds are known for their reactivity, which can lead to further chemical transformations. They are also important in the study of organic chemistry and explosive materials.