GB452934A - Improvements in or relating to the manufacture and production of alkyl halides - Google Patents

Abstract

Alkyl halides are produced by reacting aliphatic ethers with halogen-substituted organic compounds containing one or more halogen atoms attached to carbon atoms which are not adjacent to carbon atoms carrying hydrogen. Suitable halogen compounds are chloroform, carbon tetrachloride, methylene iodide, monofluortrichlormethane, difluordichlormethane, benzal chloride, benzotrichloride, naphthylmethylchloride, and mono-, di- and tri-chloracetic acid. Suitable catalysts are those having a hydrating or dehydrating action, such as oxides of barium, zinc, aluminium, silicon, titanium, zirconium and thorium, aluminium sulphate, aluminium, iron, cerium, silver and uranium phosphates, and zinc tungstate and chromate. With dimethyl ether any desired pressure may be employed, but with ethyl and higher ethers it is preferred to use pressure such as 10--30 or even 100 atmospheres to avoid production of olefines. When the starting materials are difficultly volatile reduced pressure may be employed. The temperature may be 200--500 DEG C. A small proportion of alcohol and/or steam may improve the action of the catalyst. In examples: (1) methyl chloride is made from dimethyl ether and chloroform with alumina gel as catalyst; (2) ethyl chloride is made from diethyl ether and chloroform, using cerium phosphate gel; (3) methyl chloride is made from carbon tetrachloride and dimethyl ether, using a mixed catalyst consisting of iron, cadmium, and aluminium phosphates; (4) methyl iodide is made from methylene iodide and dimethyl ether, using alumina; (5) benzaldehyde and methyl chloride are made by passing benzal chloride and dimethyl ether over alumina gel; the benzaldehyde is collected in a catch pot at 120 DEG C. and the methyl chloride may be collected in warm aniline; (6) benzaldehyde and ethyl chloride are made from benzal chloride and diethyl ether; (7) methyl chloride, benzoic anhydride, benzoic acid and methyl benzoate are made by passing benzotrichloride and dimethyl ether over precipitated alumina; (8) methyl chloride is made by passing trichloracetic acid and dimethyl ether over phosphates of iron, cadmium, and aluminium; (9) methyl fluoride and chloride are made by passing monofluortrichlormethane or difluordichlormethane and dimethyl ether over alumina.