GB981113A - Oxidation of organic thiols - Google Patents

Abstract

A process for producing aliphatic or aryl disulphides or polydisulphides (see also Division C3) comprises reacting one or more aliphatic or aryl mono- or poly-thiols, respectively, with oxygen in the presence of a catalyst comprising a tertiary amine and a cuprous salt capable of existing in the cupric state and forming with the tertiary amine a complex soluble in the reaction medium. The thiols used may be substituted by a halogen or by -OH, -OR, -COOR, -CHO, -CO, -CONH2, -CONHR, -CONR2, -CN, -SR, -SSR, -SOR, -NO2, -SO2R, -NH2, -NHR or -NR2 groups, where R is an aliphatic or aryl radical. Cuprous salts specified are cuprous chloride, cuprous bromide, cuprous sulphate, cuprous azide, cuprous acetate, cuprous propionate, cuprous palmitate and cuprous benzoate; tertiary amine complexes of cuprous nitrate and cuprous fluoride produced in situ may also be used. Tertiary-amines which may be used include aliphatic, including cycloaliphatic, and arylaliphatic tertiary-amines, ring-nitrogen heterocyclic tertiary-amines, and polyamines having one or more aliphatic or ring-nitrogen tertiary amino-radicals interconnected by one or more aliphatic or cycloaliphatic linkages. Mixtures of such tertiary-amines and/or such cuprous salts may be used. An oxygen-containing gas, e.g. air, may be employed. An exothermic reaction occurs with formation of water as a by-product, and the escape of water should desirably be prevented or controlled so as to retain in the reaction mixture one mole of water per mole of the catalyst; in batchwise operation this may be effected by carrying out the reaction under reflux conditions and/or at superatmospheric pressure and/or with cooling and/or in the presence of a desiccant. In continuous operation this may be effected by carrying out the reaction at subatmospheric pressure, by the use of azeotropic distillation or of heat, or by a controlled sweeping of the reaction mixture with an inert gas, e.g. nitrogen, helium or argon. The reaction temperature should preferably not exceed 100 DEG C. Reaction may be terminated by adding a mineral acid, which reacts with the amine and the cuprous salt, or by precipitating the product or the cuprous salt. During the reaction a different mono-thiol or di-thiol may be added to produce mixed disulphides or polydisulphides. The reaction medium may contain an inert organic solvent. Specific examples describe the preparation of (1) b -naphthyl disulphide, (2) bis-(2,6-dimethylphenyl) disulphide, and (3) bis-(2,4,6-trimethylphenyl)-disulphide, using a cuprous chloride-pyridine catalyst.ALSO:A process for producing polydisulphides (see also Division C2) comprises reacting one or more dithiols or polythiols with oxygen in the presence of a catalyst comprising a tertiary amine and a cuprous salt capable of existing in the cupric state and of forming with the tertiary amine a complex soluble in the reaction medium. When dithiols are used fusible polymers or copolymers are obtained; polythiols having three or more thiol radicals yield cross-linked insoluble polymers. The thiols used may be substituted by a halogen or by -OH, -OR, -COOR, -CHO, -CO, -CONH2, -CONHR, -CONR2, -CN, -SR, -SSR, -SOR, -NO2, -SO2R, -NH2, -NHR or -NR2 groups where R is an aliphatic or aryl radical. Cuprous salts specified are cuprous chloride, cuprous bromide, cuprous sulphate, cuprous azide, cuprous acetate, cuprous propionate, cuprous palmitate and cuprous benzoate; tertiary amine complexes of cuprous nitrate and cuprous fluoride prepared in situ may also be used. Tertiary amines which may be used include aliphatic, including cycloaliphatic, and aryl - aliphatic tertiary amines, ring - nitrogen heterocyclic tertiary amines, and polyamines having one or more aliphatic or ring-nitrogen tertiary aminoradicals interconnected by one or more aliphatic or cycloaliphatic linkages. Mixtures of such tertiary amines and/or such cuprous salts may be employed. An oxygen-containing gas, e.g. air, may be used. An exothermic reaction occurs with formation of water as a by-product, and the escape of water should desirably be prevented or controlled so as to retain in the reaction mixture one mole of water per mole of catalyst; in batch-wise operation this may be effected by carrying out the reaction under reflux conditions and/or at superatmospheric pressure and/or with cooling air and/or in the presence of a desiccant. In continuous operation this may be effected by carrying out the reaction at subatmospheric pressure, by the use of azeotropic distillation or of heat, or by a controlled sweeping of the reaction mixture with an inert gas, e.g. nitrogen, helium or argon. The reaction temperature should preferably not exceed 100 DEG C. The reaction medium may contain an inert organic solvent. Polymerization may be controlled by addition of a monothiol, and the reaction may be terminated by adding a mineral acid, which reacts with the amine and the cuprous salt, or by precipitating the product or the cuprous salt. The products may be blended with up to 75% by wt. of polymers of alkenes having 3 to 8 carbon atoms, polybutadiene, polyisoprene, polychloroprene, copolymers of butadiene and styrene or acrylonitrile, polyorganosiloxanes, polyalkylmethacrylates, polystyrene, and chlorosulphonated or chlorinated polyethylenes. One or more fillers may be added, e.g. carbon blacks and various silicas including silica aerogels, zerogels and fumed silicas, which may be treated with a hydrophobic agent such organosilicon halide, Catalpo clay, diatomaceous earth, chromic oxide, titanium dioxide, ferric oxide, calcium carbonate, cadmium sulphide, asbestos, wood flour, cellulose fibres, mineral fibres, glass fibres, alumina, lithopone, talc, and calcium silicate. One or more dyes and/or pigments and one or more plasticizers may also be added. Specific examples describe the preparation of polydisulphides from a ,a 1-dimercapto-p-xylene, toluene 3,4-dithiol, naphthalene 1,5-dithiol, ethylene dithioglycol, 1,9-nonane dithiol, 1,10-decane dithiol and 1,3-propane dithiol.ALSO:Naturally occurring thiols are removed from petroleum by treatment with oxygen in the presence of a catalyst comprising a tertiary amine and a cuprous salt capable of existing in the cupric state and of forming with the tertiary amine a complex soluble in the reaction medium.ALSO:The oxidation of organic thiols is catalysed by a tertiary amine and a cuprous salt capable of existing in the cupric state and forming with the tertiary amine a complex soluble in the reaction medium. Numerous tertiary amines and cuprous salts are specified.