GB938199A - Improvements in or relating to the preparation of nitriles - Google Patents

Abstract

A nitrile is separated from an aqueous mixture comprising the nitrile and at least one inorganic salt and/or a complex of the nitrile and an inorganic metal salt by heating the mixture with a solvent for the nitrile, which solvent forms an azeotrope with water and does not dissolve the inorganic metal salt or salts, decomposing the complex if present and removing the water and at least part of the solvent by distillation, dividing the remaining mixture into inorganic salt or salts on the one hand and nitrile or nitrile solution on the other, and optionally removing solvent from the nitrile solution. Nitriles which may be separated include acetonitrile, capronitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, sebacic acid nitrile, 2-chlorobenzonitrile, 2,4,6-trichlorobenzonitrile, 3-chloro-1-nitro-2-cyano-naphthalene, 6-chloro-2-nitrobenzonitrile, 6-bromo - 2 - nitrobenzonitrile, 6-methyl-2-nitro benzonitrile, 2,6-dinitrobenzonitrile, o-nitrobenzonitrile, 5-methyl-2-nitrobenzonitrile, 1,3-dinitro-2-cyanonaphthalene and 6-nitro-2-methoxy benzonitrile. The inorganic metal salt or salts present as such or as complexes with nitriles in the aqueous mixture may be alkali or alkaline earth metal salts, e.g. sodium potassium or calcium or copper, zinc or iron salts, or mixtures thereof. Specified salts are cuprous chloride, cuprous bromide, cuprous cyanide and the halides or cyanides of sodium or potassium. The azeotropic distillation is generally carried out at atmospheric pressure using a solvent the aqueous azeotrope of which has a boiling point of between 30 DEG and 100 DEG C. at atmospheric pressure. The solvent used is preferably not miscible with water. Suitable solvents are aromatic hydrocarbons, e.g. benzene, toluene, xylene and halogenated hydrocarbons, e.g. 1,2-dichloroethane. In the example 6-chloro-2-nitrobenzonitrile is prepared by reacting 2,3-dichloro nitrobenzene with cuprous cyanide in dimethyl formamide, the dimethyl formamide subsequently being remixed by washing with water. The wet slurry obtained consisting chiefly of a complex of 6-chloro-2-nitro-benzonitrile and cuprous chloride and containing an amount of water about equal to the amount of complex is heated with 1,2-dichloroethane, the water and part of the solvent thus being distilled off. The bottom layer of the distillate consisting of dichlorethane is continuously recycled. The nitrile solution is syphoned off the precipitated cuprous chloride, cooled, filtered and the solvent distilled therefrom. Specifications 861,898 and 861,899 are referred to.