Sulfonyl fluorides have the general formula RSOF. They can be produced by treating sulfonic acids with sulfur tetrafluoride:
Perfluorooctanesulfonyl derivatives, such as PFOS, are produced from their sulfonyl fluoride, which are produced by electrofluorination 
In the molecular biology, sulfonyl fluorides are used to label proteins. They specifically react with serine, threonine, tyrosine, lysine, cysteine, and histidine residues. The fluorides are more resistant than the corresponding chlorides and are therefore better suited to this task.
Some sulfonyl fluorides can also be used as  deoxyfluorinating reagents, such as 2-pyridinesulfonyl fluoride (PyFluor) and N-tosyl-4-chlorobenzenesulfonimidoyl fluoride (SulfoxFluor).