By oxidation of thiols

Of these the most important are the sulfonic acids In general however sulfonic acids are not prepared by oxidation of thiols Arenesulfomc acids (ArS03H) for example are prepared by sulfonation of arenes (Section 12 4)... 

The introduction of redox-sensitive linkages, such as the disulphide group, has been used to prepare liposomes that are susceptible to the lower intracellular redox potential relative to the extracellular environment. Symmetrical disulphides are synthesised by oxidation of thiol-containing structures [64, 130, 131] (see Fig. 7),... 

Thus both thiyl RS and disulfide radical are created either by oxidation of thiols or by reduction of disulfides. For small peptides such as glutathione, in the absence of oxygen and provided that the oxidant/reductant reacts only with the sulphur, the system seems totally reversible. In the presence of oxygen, RS reacts with O2 (see 2.2) and thus other oxidized functions appear. 

The catalytic oxidation of sulfur-containing compounds has been studied mostly on the examples of thioethers and thiols, which are most often encountered in petrochemical industry. Elimination of the foul odor arising from thiols (mercaptans) contained in some oils ("sweetening") is mostly carried out by oxidation of thiols to disulfides. The oxidation of sulfur salts is also of practical importance in the processing of sulfide ores and handling the... 

Disulfide formation by oxidation of thiols and its reverse are important biological processes, although nature uses much milder reagents and conditions than those depicted above. Many proteins and peptides contain free SH groups that form bridging disulfide linkages. Nature exploits this mechanism to link amino acid chains. By thus helping to control the shape of enzymes in three dimensions, the mechanism makes biocatalysis far more efficient and selective. 

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