Chlorosulfonic acid

Chlorosulfonic acid (CAS 7790-94-5), also known as chlorosulfuric acid, sulfurochloridic acid, and monochlorosulfuric acid, is a strong inorganic acid and highly reactive sulfonating and chlorosulfonating agent. It carries no assigned E-code and is handled exclusively in industrial and laboratory settings.

In pharmaceutical synthesis, it introduces sulfonate groups onto aromatic intermediates, enabling production of sulfonamide drugs and saccharin. In textile and agrochemical manufacturing, it sulfonates surfactant precursors and active ingredient scaffolds by reacting directly with C-H or O-H bonds, displacing hydrogen chloride and forming stable sulfonic acid or sulfonyl chloride derivatives.

Chlorosulfonic acid is supplied in anhydrous liquid form at technical and synthesis grades, typically in glass-lined or HDPE-lined drums and ISO containers. It falls under REACH regulation and is classified as a substance of high concern due to its corrosive and reactive profile. Suppliers should provide a current SDS and confirm compliance documentation on request.