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Desulfonation is a chemical process that removes a sulfonyl group and related sulfonate functionalities from a molecule. It encompasses removal of sulfonic acid groups (–SO3H), sulfonate esters (–O–SO2R), and sulfonyl protecting groups such as tosyl (p-toluenesulfonyl) and nosyl (2-nitrobenzenesulfonyl) from substrates. It is used to return to the parent compound or to unmask functional groups for further reactions, and is encountered in organic synthesis, polymer chemistry, and environmental catalysis.

In organic synthesis, desulfonation may be accomplished by hydrolysis under acidic or basic conditions, fusion with alkali or mineral acids, reductive methods (zinc or iron in acidic media, or borohydride), or catalytic hydrogenation using hydrogen with a metal catalyst. The choice of method depends on the substrate’s sensitivity and the sulfonyl group involved.

In protecting-group strategies, tosyl and nosyl groups can be removed to regenerate amines or alcohols under specific conditions without disturbing other functionalities.

In environmental and biological contexts, desulfonation refers to microbial or abiotic removal of sulfonate groups from sulfonated pollutants or metabolites, often yielding sulfite or sulfate.

Limitations include substrate sensitivity, competing side reactions, and potential formation of inorganic sulfate byproducts. Proper selection of solvent, temperature, and reagents is essential to achieve clean desulfonation.