Control of isomer distribution in a chlorination process of 2-chloro-6-(trichloromethyl) pyridine

摘要

The relative amounts of 5,6-dichloro-2-(trichloromethyl) pyridine and 3, 6-dichloro-2-(trichloromethyl)pyridine obtained in the chlorination of 2- chloro-6-(trichloromethyl)pyridine in the liquid phase at temperatures of about 160° C. to about 220° C. and in the presence of a metal halide catalyst, such as ferric chloride, are controlled by regulating the amount of hydrogen chloride present in the system, adding hydrogen chloride to obtain a mixture enriched in 5,6- dichloro-2- (trichloromethyl)pyridine or removing hydrogen chloride, usually by passing excess chlorine or an inert gas through the system, to obtain a mixture enriched in 3,6-dichloro-2-(trichloromethyl)pyridine.