Abstract: The invention pertains to a process for producing a disulfide dimer of hydrocarbylthiophosphonic dichloride wherein a hydrocarbylthiophosphonic dichloride is reacted with hydrogen sulfide. In the process disclosed, the reaction is conducted in the presence of a small amount of solvent which dissolves the product at high temperature and has very low solubility in the product at low temperature. In recovering the product an additional amount of solvent is added to the reaction product thereby allowing for the recovery of the product as a slurry after completion of the reaction. Optionally and preferably, a packed column is used in the process which increases the reaction rate.

Abstract: There is disclosed a process for the production of arylsulfonyl halides, e.g., benzenesulfonyl chloride. The disclosed process adds a phosphorus-containing additive, e.g., phosphorous acid, before the reaction of an arylsulfonic acid with a sulfur halide and a halogen. The phosphorus-containing additive reduces the thermal instability of the residue remaining after distillation of the arylsulfonyl halide.