GB716995A - Improvements in or relating to improvement in process for the preparation of pentachlorophenol and octachlorocyclohexenone - Google Patents

Abstract

Pentachlorophenol and octachlorocyclohexenone are prepared by reacting phenol with chlorine at an elevated temperature, e.g. 120-140 DEG C., until the chlorine content corresponds to trichlorophenol, adding a metal halide chlorination catalyst such as ferric chloride, continuing the chlorination until the products have a chlorine content corresponding to tetrachlorophenol, adding preformed octachlorocyclohexenone in an amount constituting 10 to 50 mol. per cent of the reaction mass and continuing the chlorination at 120 DEG to 140 DEG C. until the desired chlorinated compound is formed. Alternatively, where the desired product is octachlorocyclohexenone, the process may comprise chlorinating pentachlorophenol in admixture with 10 to 50 mol. per cent of preformed octachlorocyclohexenone in the presence of ferric chloride at a temperature from 120 DEG to 140 DEG C. until two mols. of chlorine per mol. of pentachlorophenol have been consumed. When the desired product is pentachlorophenol it is necessary to separate it from the octachlorocyclohexenone and other constituents of the reaction mixture, e.g. by solvent extraction or crystallization. In examples: (1) and (2) phenol is chlorinated at 130 DEG C. until trichlorophenol is formed, anhydrous ferric chloride is added and chlorination continued until a tetrachlorophenol is formed and octachlorocyclohexenone is then added and chlorination continued until the whole of the reaction mixture is converted to octachlorocyclohexenone; and (3) pentachlorophenol is chlorinated at 120-130 DEG C. in the presence of octachlorocyclohexenone until the whole of the reaction mixture is converted to octachlorocyclohexenone.