GB635201A - Improvements in or relating to the production of fluorine-containing hydrocarbon derivatives - Google Patents

Abstract

The degree of fluorination of a highly fluorinated fluorochlorohydrocarbon, defined as a product with at least the majority of chlorine or hydrogen atoms replaced by fluorine, is increased by dehydrochlorinating said fluorochlorohydrocarbon and treating the resulting unsaturated body with fluorine, cobalt trifluoride or silver difluoride. Dehydrochlorination may be effected by distillation with lime, soda lime or sodium hydroxide or by heating with aqueous, alcoholic or anhydrous caustic alkalies. Fluorination may be effected by passing gaseous fluorine through the product thus obtained, by heating it with cobalt trifluoride or silver difluoride or by passing vapours thereof over cobalt trifluoride at 320 DEG to 370 DEG C. Compounds to be treated are particularly those containing 6 to 15 carbon atom skeletons, e.g. products from the fluorination of benzotrifluoride dissolved in a highly chlorinated solvent such as pentachloroethane. In one example benzotrifluoride dissolved in pentachloroethane is treated at 60 DEG C. with fluorine gas diluted with nitrogen and the fraction of the product boiling in the range 240 DEG to 260 DEG C. is isolated and distilled with excess milk of lime to give a product of boiling range 200 DEG to 240 DEG C. which is heated with silver difluoride and distilled to give highly fluorinated products, alternatively dehydrochlorination may be effected by treatment at 50 DEG to 60 DEG C. with 3 per cent methyl alcoholic sodium hydroxide, the product being separated by the addition of water and then fluorinated as above. In the Provisional Specification a further example is given in which the fluorochloro-hydrocarbon product obtained as above from benzotrifluoride is dehydrochlorinated by distillation over soda lime.