RSO2H

RSO2H denotes sulfinic acids, a class of organosulfur compounds in which a sulfinyl group (-SO2H) is bonded to an organic substituent R. The nominal formula is R-S(=O)2-H, with sulfur in the +4 oxidation state. Sulfinic acids are structurally related to sulfonic acids but contain one fewer oxygen atom and exhibit distinct reactivity.

In most cases R is an alkyl or aryl group. The -SO2H moiety imparts acidity to the molecule, and sulfinic acids form salts with bases (RSO2−). They may exist in solution as various tautomeric or hydrated forms, and many derivatives are isolable as solids or stable solutions. Common exemplars include methane sulfinic acid (CH3SO2H) and related aryl sulfinic acids.

Preparation of RSO2H compounds typically proceeds by oxidation of thiols (RSH) or thioethers to the sulfinic acid with oxidants such as hydrogen peroxide, oxygen, or other catalysts. Other routes include hydrolysis of sulfinyl chlorides to give the corresponding sulfinic acids. These methods provide access to a wide range of RSO2H derivatives for synthetic use.

Applications and reactions: Sulfinic acids serve as versatile intermediates in organic synthesis. They can participate in sulfur-centered nucleophilic chemistry and react with electrophiles to form sulfonyl derivatives, such as sulfones and sulfonamides, and can be transformed into sulfonyl chlorides under appropriate conditions. Some sulfinic acids, notably cysteine sulfinic acid, occur as metabolites in biology and are studied in enzymology and metabolism, illustrating the relevance of this functional group beyond basic synthesis.