GB583634A - Production of chlorinated hydrocarbons - Google Patents

Abstract

Xylylene chloride is obtained by exposing a mixture of xylene and chlorine to actinic radiation in the presence of an inert diluent and a trace of phosphorous pentoxide, the reaction medium being free from iron or aluminium compounds. The xylene used may be one of the pure isomeric xylenes or a mixture of them. During the later stages of the chlorination, the chlorine, advantageously, contains a small proportion of oxygen which reduces the tendency towards over-chlorination of the reaction product. The phosphorous pentoxide which is added forms innocuous compounds with any iron or aluminium impurities. The inert diluent such as chloroform or carbon tetrachloride may comprise 60-80 per cent of the mixture. In examples: (1) chlorine is passed into reaction vessel containing p-xylene and carbon tetrachloride and 0.05 per cent phosphorous pentoxide, which is heated to reflux temperature and illuminated by artificial light or sunlight. In the later stages of the chlorination 3 per cent of air is introduced into the chlorine feed line. The p-xylylene chloride is obtained from the reaction products by frictional distillation in the presence of phosphorous pentoxide and purified by crystallization; (2) commercial xylene mixture is chlorinated as in example (1); (3) p-xylyl chloride which is obtained in (1) in addition to p-xylylene chloride is recycled in order to secure further amounts of the desired xylene chloride.