GB953554A - Improvements in or relating to a process for the manufacture of halogenated aromaticcompounds - Google Patents

Abstract

2,6-Dichlorobenzal chloride and/or 2,6-dichlorobenzyl chloride are made by reacting 2,6-dinitrotoluene or 2-chloro-6-nitrotoluene with chlorine or thionyl chloride at a temperature of at least 130 DEG C., preferably between 160 DEG and 195 DEG C. 1,2,3-trichloro benzene, 2-chloro-6-nitrotoluene and 2-chloro-6-nitrobenzyl chloride may be formed as by-products. A halogenation catalyst, such as sulphur or phosphorus trichloride, may be used and/or the reaction vessel may be irradiated with ultra-violet light. Although atmospheric pressure is usual, sub- or super-atmospheric pressure may be applied, if desired. An inert solvent, e.g. a chlorinated hydrocarbon may be present, and an inert gas such as nitrogen may be used instead of, or in addition to, an excess of chlorinating agent. 2,6-Dichlorobenzal chloride may be converted in a single step to 2,6-dichlorobenzaldoxime by reacting with hydroxylamine in an acid medium, preferably a concentrated mineral acid such as sulphuric acid, at a temperature between 30 DEG and 70 DEG C. Alternatively, 2,6-dichlorobenzal chloride may be hydrolyzed with an acid, such as sulphuric acid, or with acetic acid and zinc chloride, to 2,6-dichlorobenzaldehyde which is then converted to oxime by reaction with hydroxylamine in acid medium. Detailed examples are given. The Provisional Specification refers more generally to the halogenation of nitro- or nitro-halo-alkylbenzene with chlorine or bromine or with thionyl chloride or thionyl bromide at a temperature of at least 130 DEG C. The starting materials may also contain at least one alkoxy group or COOR group, where R is alkyl, or a group R1, OR1 or COOR1, where R1 represents phenyl which is unsubstituted or substituted only by chlorine or bromine.