Chlorosulfonation Chlorosulfonations are carried out either by direct reaction of the compound with chlorosulfonic acid or via chlorination of in-situ produced sulfonic acids with thionyl chloride. Alkyl sulfonyl chlorides can be also obtained by oxidation of thiols with chlorine. Reaction scheme Strengths - In-situ chlorinations - captive use of reagents - recycling of HCl and SO2 For specific products please check product groups sulfonic acid derivatives.