arylsulfonic

Arylsulfonic refers to organic compounds that contain a sulfonic acid group (−SO3H) directly attached to an aromatic ring. The core family consists of arylsulfonic acids, ArSO3H, and a range of derivatives including sulfonate esters and sulfonyl chlorides. Common examples are benzenesulfonic acid (PhSO3H) and p-toluenesulfonic acid (p-CH3-C6H4-SO3H). These compounds are widely used in organic synthesis and industry.

Properties of arylsulfonic acids include their status as strong Brønsted acids, with very low pKa values in water. They are typically highly water-soluble, though substitution on the ring can modulate solubility. The sulfonic acid group is strongly deactivating and meta-directing for electrophilic aromatic substitution. The ArSO3H moiety is generally stable to many conditions, contributing to the utility of these compounds as reagents, protecting groups, and intermediates.

Preparation and applications vary by substituent. They are commonly prepared by direct sulfonation of arenes with sulfuric acid or oleum. Aryl sulfonic acids are versatile in synthesis: p-toluenesulfonic acid serves as a solid, non-volatile acid catalyst; benzenesulfonic acid and related acids act as reagents and phase-transfer aids. Derivatives such as arylsulfonates function as leaving groups (tosylates) in nucleophilic substitutions, and sulfonyl chlorides (ArSO2Cl) are used in acylation and protection chemistry. Aryl sulfonates also feature in surfactants, notably alkylbenzenesulfonates. Desulfonation can occur under strong heating, but the SO3H group is generally retained under ordinary conditions.