Sulfonation is a chemical reaction in which a sulfonic acid group, SO3H, is introduced into the structure of a molecule or ion in place of a hydrogen atom. Sulfation involves the attachment of the OSO2OH group to carbon, yielding an acid sulfate, ROSO2OH, or of the SO4 group between two carbons, forming the sulfate, ROSO2OR.
Sulfonation of aromatic compounds is the most important type of sulfonation. This is accomplished by treating the aromatic compound with sulfuric acid, as in the reaction below. The product of sulfonation is a sulfonic acid.
Sulfonation may also be defined as any chemical process by which the sulfonic acid group, SO2OH, or the corresponding salt or sulfonyl halide group, for example, SO2Cl, is introduced into an organic compound. These groups may be bonded to either a carbon or a nitrogen atom. The latter compounds are designated N-sulfonates or sulfamates.
Most sulfonates are employed as such in acid or salt form for applications where the strongly polar hydrophilic SO2OH group confers needed properties on a comparatively hydrophobic nonpolar organic molecule. Some sulfonates, such as methanesulfonic and toluenesulfonic acids, are used as catalysts. The major quantity of sulfonates and sulfates is both marketed and used in salt form. This category includes detergents; emulsifying, demulsifying, wetting, and solubilizing agents; lubricant additives; and rust inhibitors. See also Organosulfur compound; Substitution reaction.
