Chlorine → Pyridine, 2,3,4,5-tetrachloro-6-(trichloromethyl)-

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Fifty grams of a mixture respectively containing about 32% 3,4,5-trichloro and about 64% 3,4,5,6-tetrachloro-2-trichloromethyl pyridine on a molar basis were charged to an electrically heated 250 ml glass batch chlorination reactor. 11/2 grams of anhydrous ferric chloride powder was charged to the reactor and chlorine at 70 grams/hour was sparged into the reactor through a bottom discharging sparger and the temperature adjusted to 200° C. The flow of chlorine was controlled so that at least a 50% excess of chlorine was present in the vent from the reactor. The reaction was allowed to proceed for 5 hours at which time the optimum yield of 3,4,5,6-tetrachloro-2-trichloromethyl pyridine was obtained at about a 94 molar percent conversion of the 3,4,5-trichloro-2-trichloromethyl pyridine. The main other product produced was pentachloropyridine. The reactor contents were then transferred to a vacuum distillation product recovery section where the lower boiling chlorinated pyridine compounds such as pentachloropyridine were separated from the 3,4,5,6-tetrachloro-2-trichloromethyl pyridine. The molar yield of 3,4,5,6 -tetrachloro-2-trichloromethyl pyridine was greater than 65% based on the reacted 3,4,5-trichloro-2-trichloromethyl pyridine. Another separation method involved hydrolyzing the 3,4,5,6-tetrachloro-2-trichloromethyl pyridine resultant mixture in concentrated sulfuric acid, for example, then a chlorinated solvent such as methylene chloride, chloroform, or perchloroethylene can be used to separate the pentachloropyridine from the resultant product of the 3,4,5,6-tetrachloro-2-trichloromethyl pyridine hydrolysis, i.e. 3,4,5,6-tetrachloro picolinic acid

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