The Dow Chemical Company

Dowelanco

Richard K Helling

Thomas J Dietsche

Philip D Grover

Terrill E Applebury

Kent P Steele

Mark L Garibaldi

Thomas G Patterson

Stewart J Campbell

Polychlorodipyridoimidazolium tetrachloroferrate compounds, such as 1,2,3,4,11-pentachloro-8-(trichloromethyl)dipyrido[1,2-a:1',2'-]imidazol-1 0-ium tetrachloroferrate, which are obtained as by-products in the preparation of polychloropyridine and polychloropicoline compounds by chlorination of many chloro(trichloromethyl)pyridine compounds in the presence of ferric chloride catalyst and can be prepared by heating a mixture of a chloro-2-(trichloromethyl)pyridine compound with a 2-chloro-5-(trichloromethyl)pyridine compound, can be converted to pentachloropyridine by chlorination at temperatures above about 230.degree. C. and pressures above about 300 psig (2.17 mPa).

Polychlorodipyridoimidazolium compounds and their use in the preparation

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.degree. C. to about 220.degree. 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.

Control of isomer distribution in a chlorination process

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Richard K Helling