RU2614151C2 - Electrochemical method of producing organic polysulphans - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing organic polysulphans with sulfur atoms content of 3-5, which comprises conducting cycloalkanes (C₅-C₇) reaction and hydrogen sulfide reaction in the presence of a background electrolyte, under conditions of electrolysis, at room temperature and atmospheric pressure, electrolysis is carried out in dichloromethane, at a platinum anode with a voltage potential of 1.8 V. Implementation area - organic electrochemistry and pharmaceutical industry.

EFFECT: improved method of producing organic polysulpfans based on hydrogen sulphide and cycloalkanes due to elimination of pre-sulfidation of the electrode surface with elemental sulfur and injection of deprotonating agent - triethylamine due to the absence of these stages' necessity and 0,4 V voltage potential decrease of the electrosynthesis conduction in dichloromethane.

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Description

The invention relates to the field of organic electrochemistry, in particular to methods for producing sulfur-containing derivatives of cycloalkanes - polysulfanes, which are used as regulators of the vulcanization of natural or synthetic rubber, components of lubricants, sulfidizing agents in the catalysis of organic reactions, in the production of sulfur cement, in the pharmaceutical industry in the role of potential antifungal, antibacterial and antitumor substances.

A known method of producing allylic polysulfanes based on disulfides of a similar structure in the presence of elemental sulfur, comprising the step of heating the reaction mixture to a sulfur melt temperature (115-120 ° C) in the absence of a catalyst for 1-2 hours, depending on the structure of the resulting polysulfane with different atomic contents sulfur, which is provided by a different ratio of disulfide: S ₈ (1: 1, 1: 2, 1: 0.6). The next stage of the process is the extraction of polysulfanes with chloroform and a mixture of aliphatic alcohols, which allows you to get individual polysulfanes with a yield of 2 to 12%. The yield of polysulfanes with the number of atoms ≥5 reaches 73.8% according to chromatographic analysis. The method allows to obtain symmetric high molecular weight polysulfanes with a number of sulfur atoms ≈4-20 without the formation of toxic by-products at atmospheric pressure (Patent US No. 8101802, 2012).

The disadvantages of this method are: elevated temperature, two-stage and duration of the process, low selectivity of the reaction in the direction of conversion of disulfides to polysulfanes with a given number of sulfur atoms.

A known catalytic method for producing organic trisulfanes by the reaction of alkyl (alkenyl) halides and elemental sulfur in the presence of tin (II) and copper (II) halides in the role of catalysts for a process carried out in a mixture of organic solvents (tetrahydrofuran and dimethyl sulfoxide) with varying ratios and temperatures from 30 to 70 ° C. The yield of sulfur-containing compounds varies from 17 to 51%; the conversion of alkyl (alkenyl) halides varies from 26 to 78% depending on the nature of the halogen-substituted hydrocarbons with high selectivity in the synthesis of trisulfanes with various hydrocarbon groups (Patent US No. 6555712, 2003).

The main disadvantages of this method are the difficulty of producing organic sulfanes with a sulfur atom content of ≥4, the need to use catalysts and toxic halogenated hydrocarbons, which increases material costs and degrades the environmental performance of the trisulfane production process.

A known method of producing organic tri- and tetrasulfanes based on alkyl (aryl) thiols and sulfur dichloride (dichlorodi (poly-) sulfane) in dry ether (tetrahydrofuran or in non-polar solvents in the presence of organic bases at room temperature. After the stage of mixing of thiols and sulfur-containing reagent is added in an equivalent amount of tertiary amine (pyridine derivative) for binding the hydrogen chloride released during the reaction. depending on the structure of the starting dihlorpolisulfana S _n Cl ₂ (where n = 1-8) may receive op anic polysulfanes with different polysulfide chains (K.-D. Gundermann, K. Humke. In Methoden der Organischen Chemie, Klamann, D., Ed .; Thieme: Stuttgart, 1985; Vol. E 11 (Teilband 1), p. 148).

The disadvantages of the described method include the difficulty of obtaining commercially inaccessible sulfur-containing reagents S _n Cl ₂ (where n = 3-8) and the need to capture toxic hydrogen chloride, which leads to a multi-stage process and increases the cost of synthesized compounds.

The method closest in technical essence is the electrochemical method for producing a mixture of organic di-, tri- and tetrasulfanes, including the interaction of aliphatic, aromatic and fatty aromatic thiols with an electro-generated sulfur dikation under electrolysis conditions at a potential of 2.2 V, at room temperature and atmospheric pressure. The result is mainly organic trisulfanes, the yield of which varies from 19 to 80% (G. Le Guillanton. Electrochemical activation of sulfur in organic solvents - new syntheses of thioorganic compounds with a sacrificial carbon-sulfur electrode // Sulfur reports, 1992. V. 12 (2) .Pp. 405-435).

The disadvantages of this method are: a high value of the potential for electrolysis, which contributes to an increase in energy consumption; the complexity of manufacturing a serographite electrode; the use of organic bases and the difficulty of obtaining organic pentasulfanes.

The technical problem is the development of an electrochemical method aimed at obtaining organic symmetric polysulfanes with a content of sulfur atoms 3-5 from hydrogen sulfide and cycloalkanes in methylene chloride at room temperature and atmospheric pressure.

EFFECT: improved method for producing organic polysulfanes based on hydrogen sulfide and cycloalkanes due to the elimination of preliminary sulfidation of the electrode surface with elemental sulfur and the introduction of a deprotonating agent, triethylamine, since these steps are not necessary and the potential for electrosynthesis in methylene chloride is 0.4 V.

It is achieved by the fact that in the proposed method, which involves carrying out the reaction of cycloalkanes (C ₅ -C ₇ ) and hydrogen sulfide under electrolysis conditions on a platinum anode with a reagent oxidation potential of 1.8 V, in methylene chloride, in the presence of a background electrolyte, at room temperature and atmospheric pressure, a mixture of organic polysulfanes with a content of sulfur atoms of 3-5 is obtained, followed by the isolation of reaction products.

This method is based on the ability of hydrogen sulfide to oxidize on a platinum anode at a potential of E _pa = 1.8 V in methylene chloride against the background of n-tetrabutylammonium perchlorate, which leads to the formation of thiyl radicals and their subsequent interaction with cycloalkane C ₅ -C ₇ , organic symmetric polysulfanes with a content of sulfur atoms of 3-5 at room temperature and atmospheric pressure.

Based on experimental data, we can propose a scheme of the above process (for example, cycloheptane):

The cycloalkanethiols formed in the first stage at the electrolysis potential are converted into the corresponding dicycloalkyl disulfides. In parallel, thiyl radicals generated from hydrogen sulfide during its oxidation dimerize with the formation of unstable disulfane (H ₂ S ₂ ), which leads to an increase in the sulfide chain to tri- (H ₂ S ₃ ), polysulfanes (HS _n H) and the accumulation of elemental sulfur. Dicycloalkyl disulfides and cycloalkanethiols react with elemental sulfur to produce a mixture of reaction products containing organic polysulfanes containing 3-5 sulfur atoms.

The current yield of organic polysulfanes depends on the cycle size of the starting substrate (cycloalkane C ₅ -C ₇ ) and varies from 14.6 to 33.2%. The selectivity in this direction of the reaction of cycloalkanes and hydrogen sulfide is: C ₅ - 61.6%; C ₆ - 50.9%; C ₇ - 58.0%.

The method is as follows.

Example 1. Obtaining organic polysulfanes with a content of sulfur atoms 3-5 from hydrogen sulfide and cycloheptane in methylene chloride.

The method of producing organic polysulfanes from hydrogen sulfide and cycloheptane involves pre-drying H ₂ S, introducing an organic solvent and background electrolyte into the electrolyzer, immersing the electrodes, setting the anode potential (1.8 V), introducing cycloheptane, supplying hydrogen sulfide at a certain speed and carrying out electrolysis at the exception of the stage of modifying the surface of the electrode with sulfur and the absence of a deprotonating agent, triethylamine.

30 ml of cycloheptane and 70 ml of purified and well-dried methylene chloride were added to a diaphragmless electrolyzer equipped with a bubbler for introducing hydrogen sulfide and designed for the functioning of a three-electrode electrochemical cell with a platinum working and auxiliary electrodes, a surface area of S = 700 mm ² 3.5 g of n-tetrabutylammonium perchlorate).

Hydrogen sulfide was fed continuously for 4 hours at a rate of 3 L / h with vigorous stirring. The electrolysis was started at a potential of 1.8 V relative to the reference electrode (silver chloride in the US KCl solution with a waterproof diaphragm, necessary for electrolysis in organic solvents). The reaction mixture was kept at room temperature for 4 hours. Electrolysis was carried out at a potential of 1.8 V, which reduces the anode overvoltage by 0.4 V due to the electrochemical oxidative activation of hydrogen sulfide on a platinum anode.

N-tetrabutylammonium perchlorate was precipitated with pentane. Then pentane was distilled off at a temperature of 36 ° C, methylene chloride at 41 ° C, cycloheptane at 118 ° C under reduced pressure. Received products - cycloheptanethiol with a yield of 19.8% vol. dicycloheptyl disulfide with a yield of 17.8% vol. and a mixture of organic polysulfanes with a content of sulfur atoms of 3-5 - 33.2% vol .. Compounds were identified by cyclic voltammetry, IR spectroscopy, high resolution mass spectrometry and X-ray fluorescence analysis.

The proposed method allows to simplify the process of producing organic polysulfanes with a content of sulfur atoms 3-5, to achieve high selectivity of the process, to expand the range of target products (along with tri- and tetra-receive pentasulfanes) with an increase in the duration of the electrolysis process.

Information sources

1. Patent US No. 8101802, 2012

2. Patent US No. 6555712, 2003

3. K.-D. Gundermann, K. Humke. In Methoden der Organischen Chemie, Klamann, D., Ed .; Thieme: Stuttgart, 1985; Vol. E 11 (Teilband 1), p. 148.

4. G. Le Guillanton. Electrochemical activation of sulfur in organic solvents - new syntheses of thioorganic compounds with a sacrificial carbon-sulfur electrode // Sulfur reports, 1992. V. 12 (2). Pp. 405-435 (prototype).

Claims (1)

A method of producing organic polysulfanes, including the reaction of cycloalkanes (C ₅ -C ₇ ) and hydrogen sulfide under electrolysis, in the presence of a background electrolyte, at room temperature and atmospheric pressure, characterized in that the electrolysis is carried out in methylene chloride, on a platinum anode at potential 1 , 8 V, in the absence of a deprotonating agent, triethylamine, without preliminary modification of the electrode surface with sulfur.