sulfoxide

A sulfoxide is an organosulfur compound containing the sulfoxide functional group, R-S(=O)-R', in which the sulfur atom is bonded to two carbon substituents and double-bonded to oxygen. The sulfur is in the oxidation state +4. The S=O bond is highly polar, and the group can be chiral when R and R' are different, giving rise to enantiomeric sulfoxides that are useful as ligands and chiral auxiliaries.

Formation of sulfoxides is typically achieved by the selective oxidation of sulfides (thioethers) using oxidants such as m-chloroperbenzoic acid, hydrogen peroxide with suitable catalysts, or Oxone. Careful control is required to avoid overoxidation to sulfones. Common examples include dimethyl sulfoxide (DMSO) and diaryl sulfoxides.

Dimethyl sulfoxide (DMSO) is a prominent sulfoxide and a widely used solvent. It is a polar aprotic solvent with high boiling point and strong water miscibility, often employed in organic synthesis, biochemistry, and pharmaceutical formulation. Other sulfoxides serve as solvents, reagents, or ligands in coordination chemistry and catalysis.

Reactivity of sulfoxides includes transformations such as the Pummerer rearrangement, oxidation to sulfones, and various reductions back to sulfides. They can act as ligands through the sulfoxide oxygen or, in some cases, the sulfur atom, stabilizing metal centers.

Applications span solvent use (notably DMSO), roles as chiral auxiliaries and ligands, and involvement in pharmaceutical chemistry as metabolites or active components. Safety considerations follow those for polar organic solvents; handling guidelines focus on typical solvent hazards and skin exposure concerns.