ONH2

ONH2 is a shorthand notation used in chemical literature to denote the hydroxylamine molecule in SMILES form, representing HO-NH2. Its conventional chemical formula is NH2OH. Hydroxylamine is a small, highly reactive, water-soluble compound that serves as a versatile reagent and intermediate in organic and inorganic synthesis.

In structure and properties, ONH2/HNH2OH is a polar, protonatable species with one nitrogen bearing two hydrogens and one hydroxyl group. It acts as a weak reducing agent and participates readily in condensation reactions, most notably in the formation of oximes from carbonyl compounds (R-CO-R' + NH2OH → R-CH=NOH). It also serves as a precursor to hydroxamic acids and various nitrogen-oxygen derivatives. Because of its instability, hydroxylamine is usually handled as a solution or as a salt (such as hydroxylamine sulfate) rather than as the free base.

Production and handling generally involve partial or controlled reduction of nitrite or related nitrogen oxides in aqueous media, with careful control of temperature and pH. In practice, hydroxylamine is often generated in situ for specific reactions due to its propensity to decompose or react, especially in concentrated form.

Safety and hazards are important: hydroxylamine and its salts can be toxic and sensitive to shock or friction, and concentrated samples can pose explosion risks, particularly in the presence of acids or oxidizers. Appropriate engineering controls, compatible materials, and personal protective equipment are essential when working with ONH2.

See also: hydroxylamine, oximes, SMILES notation, hydroxamic acids.