CS229033B1 - A method for the partial reduction of dinitrodiphenylsulfides, sulfoxides and sulfones - Google Patents

Abstract

A method for the partial reduction of dinitrodiphenyl sulfides, sulfoxides and sulfones by heating a mixture of water, a selected dinitro compound, an alkali carbonate, hydroxide or ammonia and a ferrous salt to a temperature between 40 °C and the boiling point of the reaction mixture, optionally in the presence of organic solvents or surface-active additives with wetting effects.

Description

The invention relates to the partial reduction of dinitrodiphenylsulfides, -sulfoxides and -sulfones with ferrous salts.

Nitroaminodiphenylsulfides, -sulfoxides, and in particular -sulfones are important semi-finished products in tar dye chemistry and can also be used in the preparation of agrochemicals, organic polymers and other branches of the chemical industry.

The partial reduction of the respective dinitro compounds by sulphides is considered to be the most industrially viable way of their production. For example, DOS 2 916 815 from 1979, protects the process of partial reduction of 4,4'-dinitrodiphenylsulfide and -sulfone with sodium bisulfide in ammonia. As all alternatives to sulphide reduction, this procedure is also accompanied by the potential danger of toxic endangering of the cell operator by the sulphide itself or by hydrogen sulphide released from it by hydrolysis or other decomposition.

We have now found a process for the partial reduction of dinitrodiphenylsulfides, -sulfoxides and -sulfones of the present invention, which comprises heating a mixture of water, a selected dinitro compound, an alkali carbonate, hydroxide or ammonia and a ferrous salt to a temperature between 40 ° C. C to the boiling point of the reaction mixture, optionally in the presence of organic solvents or surfactants with a wetting action, 5 to 7 moles per mole of NOg being used,

Among the alkaline reagents, sodium, potassium and ammonium carbonates, hydroxides, phosphates, ammonia and mixtures thereof are suitable. Of the ferrous salts, both inorganic and organic salts are suitable, for example chloride, sulfate, acetate, and šlavelan.

Particularly preferred is the use of green vitriol or waste.

The order in which the reaction components are mixed is not critical to the yield of the reduction.

In cases where ferrous salts and / or alkaline reagents were added only at the reaction temperature, the content of accompanying impurities - mainly composed of diamino compounds - was minimal.

The presence of organic solvents or surfactants as reducing aids can also shorten the reaction time; satisfactory results are achieved without them.

The starting dinitro compounds are practically insoluble in water, so that the reaction in the aqueous medium itself takes place in suspension. During the reduction, solid pulverulent iron oxides are formed and mixed with suspended reducing products, one of the known separation processes may be used to separate both solid components, for example by digesting the isolated mixture with an organic solvent into which the nitroamino product is passed. In cases where it is reduced in the presence of an organic solvent or, if appropriate, a solvent mixture, the reduction is based on a nitroamino solution. Nitroaminoleate solutions can be vaporized by the cell or used for further synthesis.

Another advantage of the process according to the invention is a significant improvement of the operating conditions at said partial reductions, the elimination of the possibility of a toxic hazard to the operator, or an improvement in the economics of production when using waste green vitriol.

Example 1

27.6 g of powdered 4,4'-dinitrodiphenylsulfide (0.1 mol) are suspended in 500 ml of water, 167 g of crystalline ferrous sulphate (Fe (SO 4) ₂ ) are added. H 2 O 3 is heated to 60 ° C and aqueous 25% NH 4 OH is added at this temperature and with stirring of the reaction mixture until alkaline (pH 8.5); the mixing time is 30 minutes. The reaction mixture was then heated to 80 ° C and filtered. The separated solid consists of iron oxides and 4-nitro-4-aminodiphenylsulfide. Extraction with dioxane separates the product from the oxides. Evaporation of the extract gave 96% of theory of crude 4-nitro-4 ' -aminodiphenylaulfides. According to chromatographic analysis, it contains a small amount of unreacted 4,4'-dinitrodiphenylsulfide and 4,4-diaminodiphenylsulfide.

Example 2

6.96 g of 4,4-dinitrodiphenyl sulfone (0.02 mol) are suspended in 100 ml of water, the suspension is heated to 70 [deg.] C. with stirring, and a total of 37.8 g of green vitriol and 75.8 g of potassium sulfate are added alternately at this temperature. mL of aqueous 25% NH 4 OH. After mixing the components, the reaction mixture is heated at 80 ° C for 15 min, then the mixture of solid iron oxides and 4-nitro-4-aminodiphenylsulfone is filtered off; extraction of the solid with dimethyl sulfoxide gave 97% of theory of crude 4-nitro-4-aminodiphenylsulfone.

Claims (3)

SUBJECT OF THE INVENTION Process for the partial reduction of nitrodiphenylsulfides, -a-sulfoxides and -sulfones, characterized in that the water, the selected dinitro compound, the alkali carbonate, hydroxide or ammonia and the ferrous salt are heated to a temperature between 40 ° C to the boiling point of the reaction mixture optionally in the presence of organic solvents and / or surface active ingredients with a wetting action, wherein the iron salts are used from 5 to 7 moles relative to 1 mol NO ₂ · 2. Process according to claim 1, characterized in that the alkali or the ferrous salt or both components are added to the other components only after heating to the reaction temperature. Method according to Claims 1 and 2, characterized in that green vitriol which is removed from chemical products such as titanium dioxide or from pickling of metallurgical materials is used as reducing agent.