PRODUCTION OF ARYLPHOSPHONIC DICHLORIDE AND DIARYLPHOSPHINIC CHLORIDE

PROBLEM TO BE SOLVED: To industrially and advantageously produce the subject compound useful as a raw material, etc., for a flame retardant for resins, an antioxidant, a modifier, etc., under mild conditions by chlorinating an arylphosphonothioic dichloride, etc., in the presence of water and then partially hydrolyzing the resultant product with the water. SOLUTION: An arylphosphonothioic dichloride or a diarylphosphonothioic chloride is chlorinated in the presence of water in an equiv. amount of 1-1.1 times based on the compound according to formula I [(n) is 1 or 2] to provide an aryltetrachlorophosphorane or a diaryltrichlorophosphorane, which is then partially hydrolyzed with the water present in the reactional system according to reaction represented by formula II. Otherwise, sulfur monochloride is separated after completing the chlorinating reaction and the unreacted substance corresponding to water, accompanied with the chlorine gas and reduced during the chlorinating reaction is treated with sulfur dioxide to afford the objective compound useful as a raw material, etc., for a flame retardant for fibers, plastics, etc., an antioxidant or a modifier.