Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/23—Oxidation

Definitions

• the present invention relates to a method for preparing alkanesulfonyl halides, particularly chlorides of the general formula RSO2Cl and alkanesulfonic acids of the general formula RSO3H. More particularly, this invention concerns a method for producing alkanesulfonyl halides and alkanesulfonic acids from alkanethiols or dialkyl disulfides without the formation of undesirable side-products and by-product hydrogen halide.
• Alkanesulfonyl chlorides also known as alkyl sulfonyl chlorides
• alkyl sulfonyl chlorides are known for their utility in imparting functionality into various compounds or as intermediates to modify various compounds, including pharmaceuticals, agricultural chemicals, photographic chemicals and the like, in order to increase their efficacy, to protect sensitive functional groups during certain processing steps, or to improve the recovery and purity during isolation procedures.
• Alkanesulfonic acids also known as alkyl sulfonic acids
• alkyl sulfonic acids are known for their utility as acids and as solvents or catalysts for the preparation of a wide variety of compounds, including pharmaceuticals, agricultural chemicals, photographic chemicals, chemicals for the electronics industry and the like.
• Giolito discloses the continuous preparation of methanesulfonyl chloride by reacting methanethiol and chlorine in saturated aqueous hydrochloric acid containing dispersed methanesulfonyl chloride in an agitated, baffled columnar reactor.
• alkanesulfonyl chlorides by reacting alkanethiols or dialkyl disulfides with chlorine is the formation of undesirable side-products arising from the chlorination of the alkyl side-chain. This problem becomes particularly serious in the preparation of alkanesulfonyl chlorides in which the alkyl side-chain contains two or more carbon atoms.
• Alkanesulfonic acids have been produced without any attendant production of hydrogen chloride by several different methods: sulfoxidation of alkanes; catalyzed air oxidation of alkanethiols and dialkyl disulfides; catalyzed hydrogen peroxide oxidation of alkanethiols and dialkyl disulfides; and anodic oxidation of dialkyl disulfides.
• the methods are illustrated by the general equations below.
• sulfoxidation shares some of the disadvantages of sulfochlorination processes; specifically, poor selectivity for the terminal carbon with alkanes containing three or more carbon atoms, multiple sulfonation, a requirement for highly pure alkane feed to minimize contamination of the desired alkanesulfonic acid with other alkanesulfonic acids, and the fact that sulfoxidation produces only alkanesulfonic acids and is not suitable for production of alkanesulfonyl chlorides.
• Catalyzed air oxidation of alkanethiols and/or dialkyl disulfides to alkanesulfonic acids has been described in U.S. Patent Nos. 2,489,316, 2,489,317, 2,727,920 and 3,392,095.
• the catalyst is a nitrogen dioxide (NO2 or N2O4).
• NO2 or N2O4 nitrogen dioxide
• catalyzed air oxidation is highly selective and produces much less sulfuric acid than does sulfoxidation -- typically 1-2 percent by weight in the crude alkanesulfonic acid -- the sulfuric acid levels are still too high for electrochemical applications.
• the catalyzed air oxidation of alkanethiols or dialkyl disulfides produces only alkanesulfonic acids and is not capable of producing alkanesulfonyl chlorides.
• Catalyzed hydrogen peroxide oxidation of alkanethiols and/or dialkyl disulfides has been disclosed in French published patent application No. 1,556,567, in German published patent application Nos. 2,504,201, 2,504,235 and 2,602,082 and in U.S. Patent Nos. 3,509,206, 4,052,445 and 4,239,696.
• the catalyst used is either an ammonium or alkali molybdate or tungstate or the alkanesulfonic acid itself. Nielsen (U.S. Patent No.
• a continuous method for preparing an alkanesulfonyl chloride of the formula RSO2Cl or an alkanesulfonic acid of the formula RSO3H where R is a nonhalogenated or unsubstituted alkyl group having one to 20 carbon atoms, in high yield which comprises passing a mixture of an alkanethiol or dialkyl disulfide in an aqueous hydrochloric acid-containing medium into an electrolysis zone or chamber and continuously removing the electrolyzed product mixture, from which the alkanesulfonyl chloride or alkanesulfonic acid product can be recovered.
• the aqueous hydrochloric acid electrolyte containing alkanesulfonic acid and/or suspended unconverted alkanethiol or dialkyl disulfide may be recycled to the electrolysis zone.
• Alkanesulfonyl bromides of the general formula RSO2Br or alkanesulfonic acids of the general formula RSO3H, where R is the same as described above, may also be prepared according to the method of this invention by replacing the hydrochloric acid in the aqueous electrolyte medium by hydrobromic acid.
• the yields of the alkanesulfonyl bromides or alkanesulfonic acids which are obtained using hydrobromic acid instead of hydrochloric acid are low due to the incomplete oxidation of the reactants.
• alkanethiol also known as alkyl mercaptan
• dialkyl disulfide reactants which can be employed in the process of this invention may be represented by the formula RSX, where X is hydrogen or a radical of the formula SR′ and where R and R′ are alkyl groups having one to 20 carbon atoms, and preferably one to 12 carbon atoms.
• R and R′ can be the same or different alkyl groups, but are preferably the same.
• the alkyl groups may be branched or straight-chain.
• the preferred reactants are methanethiol and dimethyl disulfide.
• the process of this invention is not limited and is useful for producing the corresponding alkanesulfonyl chlorides and alkanesulfonic acids using reactants such as ethanethiol, the propanethiols, the butanethiols, the pentanethiols, the hexanethiols, the heptanethiols, the octanethiols, the nonanethiols,the decanethiols, the dodecanethiols, diethyl disulfide, dipropyl disulfides, dibutyl disulfides, dioctyl disulfides, and the like.
• the electrolytic oxidation is carried out in a medium comprising aqueous hydrochloric acid or an aqueous mixture of hydrochloric acid and the corresponding alkanesulfonic acid.
• concentration of hydrogen chloride in the hydrochloric acid-containing medium should be between about eight percent by weight and the saturation concentration of hydrogen chloride in the aqueous medium at the temperature of the reaction medium in the electrolysis chamber.
• concentration of hydrogen chloride in the reaction medium is from about 20 percent by weight to about 38 percent by weight with higher concentrations being preferred in order to increase the conductivity of the electrolyte.
• the concentration of hydrogen chloride in an aqueous solution of alkanesulfonic acid varies as the concentration of the alkanesulfonic acid varies, decreasing as the concentration of the alkanesulfonic acid increases (for example: the concentration of hydrogen chloride varies from about 15 percent by weight at the methanesulfonic acid concentration of 36 percent by weight to about eight percent by weight at a methanesulfonic acid concentration of 75 percent by weight at a temperature of 85 degrees Centigrade).
• the preferred concentration of hydrogen chloride in the aqueous reaction medium is between at least eight percent by weight and the saturation concentration of hydrogen chloride in the aqueous alkanesulfonic acid-containing reaction medium at the preferred temperature of the reaction medium in the electrolysis chamber.
• the alkanethiol or dialkyl disulfide reactant can be previously mixed with the aqueous hydrogen chloride-containing medium to provide a stable suspension of the alkanethiol or dialkyl disulfide in the aqueous medium prior to addition to the electrolysis chamber or the alkanethiol or dialkyl disulfide and the aqueous hydrogen chloride-containing medium can both be added separately to the electrolysis chamber.
• the alkanethiols are slightly soluble in the hydrogen chloride-containing medium, but the longer chain length alkanethiols and the dialkyl disulfides are relatively insoluble, so that a suspension must be formed in the aqueous hydrogen chloride-containing medium.
• the preferred reactants methanethiol (methyl mercaptan) and dimethyl disulfide are relatively volatile, low boiling liquids. Therefore, if the electrolysis chamber is not enclosed, it is desirable to provide a means for condensing the volatile reactants and returning them to the electrolysis chamber such as a reflux condenser to prevent loss of the reactants during the vigorous exothermic reaction.
• the cell voltage which is used can be from about 2 volts to about 5 volts, and the preferred cell voltage which is used is from about 2.3 volts to about 3 volts.
• the current density which is used can be about 0.02 ampere per square centimeter to about one ampere per square centimeter.
• the preferred current density is about 0.1 ampere per square centimeter to about 0.5 ampere per square centimeter.
• the current density be maintained at about 0.5 ampere per square centimeter.
• the solubility of hydrogen chloride in the aqueous alkanesulfonic acid-containing electrolyte medium decreases as the concentration of the alkanesulfonic acid increases, which results in an increase in the cell voltage when the current density is maintained constant.
• the current density be decreased as the concentration of the alkanesulfonic acid in the aqueous electrolyte increases so that the cell voltage remains constant within the preferred range of about 2.3 volts to about 3 volts.
• the current used be sufficient to provide a slight excess of electrical energy over that required to completely oxidize the alkanethiol or the alkyl disulfide introduced into the electrolysis zone. That is, at least six Faradays (electrical equivalents) should be provided for every gram-mole of alkanethiol introduced into the electrolysis chamber, and at least ten Faradays should be provided for each gram-mole of dialkyl disulfide introduced into the electrolysis chamber. It is preferred that the electrical power provided be from about 0.5 percent to about 5 percent in excess of that required to completely oxidize the alkanethiol or dialkyl disulfide reactant introduced into the electrolysis chamber.
• the residence time of the reactants in the electrolysis zone is the time required to convey the necessary current to effect the complete oxidation of the reactants and can vary from about 15 seconds to several minutes.
• the temperature at which the electrolytic oxidation is carried out can be from about zero degrees Centigrade to about 120 degrees Centigrade. However, at temperatures less than about 15 degrees Centigrade the electrolysis reaction is adversely affected by a decrease in the solubility of the alkanethiol or dialkyl disulfide reactants in the aqueous hydrochloric acid-containing medium and by a decrease in the conductivity of the aqueous hydrochloric acid-containing electrolyte. At temperatures greater than about 100 degrees Centigrade the electrolysis reaction is adversely affected by a decrease in the solubility of hydrogen chloride in the aqueous medium resulting in a decrease in the conductivity of the aqueous electrolyte.
• the yield of the product alkanesulfonyl chloride is adversely affected by subsequent hydrolysis of the alkanesulfonyl chloride in the aqueous medium to produce the corresponding alkanesulfonic acid. Therefore, when the alkanesulfonyl chloride is the desired product, it is preferred that the electrolysis reaction be carried out at a temperature of about 15 degrees Centigrade to about 40 degrees Centigrade, and most preferably at a temperature of about 18 degrees Centigrade to about 25 degrees Centigrade.
• the alkanesulfonyl chloride is hydrolyzed very slowly in the aqueous reaction medium to produce the corresponding alkanesulfonic acid. Therefore, when the alkanesulfonic acid is the desired product, it is preferred that the electrolysis reaction be carried out at a temperature of about 50 degrees Centigrade to about 100 degrees Centigrade, and most preferably at a temperature of about 75 degrees Centigrade to about 90 degrees Centigrade.
• the method of this invention may be carried out at subatmospheric, atmospheric, or superatmospheric pressures. It is preferred that the practice of this invention be carried out at substantially atmospheric pressure.
• the aqueous hydrochloric acid in the electrolyzed product mixture may be recovered, after separation of the product alkanesulfonyl chloride or alkanesulfonic acid by methods known to those skilled in the art, and recycled to the electrolysis chamber if so desired.
• Methods for the separation of the product alkanesulfonyl chloride from an aqueous hydrochloric acid solution are known in the art and primarily involve decantation. As described in U.S. Patent 3,626,004, when the alkanesulfonyl chloride has from 1 to 4 carbon atoms, the specific gravity thereof is greater than that of the concentrated aqueous hydrochloric acid medium.
• the specific gravity thereof is less than that of the aqueous hydrochloric acid medium, and the product will rise to the top of the separation zone or chamber.
• the separation of the product and its decantation is facilitated by maintaining a sufficient differential of specific gravities between the aqueous medium and the alkanesulfonyl chloride product layers by continuously or intermittently withdrawing a small portion of the aqueous reaction medium from the product separation zone and/or continuously or intermittently adding fresh water or aqueous hydrochloric acid solution to maintain the specific gravity differential and the proper liquid level in the separation zone.
• the electrodes used in the method of this invention can be constructed of any materials which are both highly conductive and compatible with the alkanethiol or dialkyl disulfide reactants, the aqueous hydrochloric acid-containing electrolyte, chlorine, hydrogen, and the product alkanesulfonyl chlorides and alkanesulfonic acids.
• the electrodes may be constructed from, for example, platinum, gold, graphite, titanium plated with platinum, and the like. It is preferred that the anode used by graphite or a material similar to the various dimensionally-stable metal oxide/metal anodes which have been developed for use in the electrolysis of aqueous brine solutions, for example, titanium coated with titanium oxide and/or ruthenium oxide. It is preferred that the cathode used be constructed of graphite or platinum.
• the design of the electrolysis chamber of the method of this invention is not critical. However, the design of the electrolysis chamber should provide sufficient turbulence, either by mechanical agitation, by static mixing, or by the turbulence produced by the evolution of gaseous hydrogen from the cathode surface, to maintain the slightly soluble alkanethiol or dialkyl disulfide reactant in a highly dispersed state within the electrolysis chamber.
• the electrolysis chamber may consist of a single compartment or may consist of two or more compartments in which the anode compartments and cathode compartments are separated by diaphragms or selectively permeable membranes such as are employed in the manufacture of chlorine and sodium hydroxide from aqueous brine solutions.
• the method may be carried out in a single electrolysis chamber or may utilize two or more electrolysis chambers in series or parallel.
• the method of the present invention has several advantages over the chlorine oxidation methods of Guertin, Giolito, Hubennett, or Gongora, et al., in that the method of the present invention does not result in the net production of hydrogen chloride as a by-product, thus eliminating the need for disposal of the by-product, hydrogen chloride.
• the by-product hydrogen produced in the process of this invention can be recovered and used for fuel.
• the addition of gaseous chlorine to the aqueous reaction media embodied in the aforementioned methods of Guertin, Giolito, Hubennett or Gongora, et al. can result in localized regions of either high chlorine concentration or chlorine deficiency in the liquid reaction medium, even under conditions of high mechanical agitation.
• the method of the present invention has several advantages over the other aforementioned prior-art methods which do not involve chlorine oxidation.
• the method of this invention can produce either an alkanesulfonyl chloride or an alkanesulfonic acid in a single step which the other aforementioned prior-art methods cannot do, in yields of at least 80% and generally in yields of 90% or greater.
• the method of this invention produces only a single isomeric alkanesulfonyl chloride or alkanesulfonic acid corresponding to the alkanethiol or dialkyl disulfide isomer used as the reactant, and the method of this invention produces no detectable chlorinated hydrocarbon side-products.
• the method of this invention has several advantages over the aforementioned electrolytic oxidation methods of Brown or Tomilov (Compare Comparative Example 1, illustrating the batchwise method of Tomilov, with Examples 2 to 6 below which illustrate the method of this invention).
• the current efficiency is high; i.e., at least 70% and usually at least 90%, based on the amount of product alkanesulfonyl chloride or alkanesulfonic acid produced and the electrical power consumed.
• the yield of the product alkanesulfonyl chloride or alkanesulfonic acid is also high; i.e., at least 80% and usually at least 95%, based on either the alkanethiol or dialkyl disulfide reactant.
• the method of this invention can produce either an alkanesulfonyl chloride or an alkanesulfonic acid, whereas the method of Brown produces only alkanesulfonic acids and the method of Tomilov produces only 2-chloroalkanesulfonyl chlorides.
• This example illustrates the low current efficiency obtained in the preparation of methanesulfonyl chloride by the batchwise electrolytic oxidation of dimethyl disulfide in a concentrated hydrochloric acid medium according to the method of Tomilov.
• Dimethyl disulfide (5.30 gm) and concentrated hydrochloric acid (37.1 percent HCl by weight, 35 ml, 41.30 gm) were combined in a three-necked round bottom flask equipped with a TEFLON®-coated magnetic stirring bar, a thermometer, a reflux condenser and two platinum electrodes, each consisting of a 1.5 cm diameter platinum disc spot-welded to the end of a 10 cm length of 1 mm diameter platinum wire.
• the electrodes were suspended in the flask by inserting the wire leads through a rubber stopper inserted in the center neck of the flask. The electrodes were spaced about 4-5 mm apart.
• the mixture was electrolyzed for six hours with vigorous stirring using a current of 2.5 amperes at a voltage of 5.0 volts D.C. A 17 percent yield of methanesulfonyl chloride was obtained, and the current efficiency was only about 44 percent.
• a continuous-flow electrolysis cell was constructed from 30 mm diameter glass tubing with a glass inlet tube located on one side about 1 cm up from the bottom of the cell and a liquid take-off tube (equipped with a siphon-break and a shut-off valve) located on the opposite side of the cell about 5 cm up from the bottom of the cell.
• a 14/20 ground-glass side-neck was located on the inlet side about 8 cm up from the bottom of the cell, and a threaded thermometer adapter was attached to the front of the cell about 7 cm up from the bottom of the cell.
• the cell was joined to a 29/42 ground-glass outer joint at the top into which fit a TEFLON® stopper.
• the stopper was equipped with two small holes (less than 1 mm in diameter) centered about 1 cm apart.
• the electrode assembly which consisted of two parallel platinum plates (1.1 cm x 4.4 cm active surface) embedded in a TEFLON® bar along the length on each side of the bar to secure the plates 4 mm apart, was suspended in the cell by passing the 1 mm diameter platinum wire lead from each electrode through the holes in the TEFLON® stopper.
• the electrode leads were connected to a variable voltage DC power source.
• the cell was equipped with a TEFLON®-coated magnetic stirring bar, a thermometer, and a reflux condenser.
• the inlet of the cell was connected to the discharge side of a peristaltic pump using VITON tubing.
• the suction side of the peristaltic pump was connected to a feed reservoir by a length of VITON tubing.
• a 50 ml Erlenmeyer flask immersed in an ice bath served as the receiver for the liquid effluent from the liquid take-off tube of the electrolysis cell.
• This example illustrates the production of n -propanesulfonyl chloride by the electolytic oxidation of n -propanethiol by the method of this invention.
• n -propanethiol (0.80 gm) and 100 ml of concentrated hydrochloric acid (37.1 percent HCl by weight) was passed through the apparatus used in Example 2 at a rate of 5 ml/min.
• the electrolysis cell was immersed in a water bath to maintain the temperature of the mixture in the cell at 22-25 degrees Centigrade.
• a current of 3.50 amperes at 2.60 volts DC was passed through the cell to produce n -propanesulfonyl chloride (CH3CH2CH2SO2Cl) in 80 percent yield at a current efficiency of 73 percent. No products exhibiting chlorination of the propyl group were detected.
• a commercially available small, undivided (i.e., no membrane between the electrodes), plate-and-frame electrochemical cell (MICRO FLOW CELL manufactured by Electro Cell AB of Akersberga, Sweden) was used.
• the cell was constructed from TEFLON® except for the electrodes and the mounting bolts.
• the anode was a dimensionally-stable ruthenium oxide/titanium oxide on titanium anode (obtained from Eltech Systems), and the cathode consisted of titanium plated with platinum.
• the active electrode surface was 10 square centimeters, and the inter-electrode spacing was 4 mm.
• the liquid volume of the cell was about 4 ml.
• the cell was run at a constant current of 3.50 amperes and a voltage of 2.40-2.50 volts DC.
• the feed to the cell consisted of a combination of a fresh feed mixture of dimethyl disulfide (one percent by weight) and concentrated hydrochloric acid (37.1 percent HCl by weight) and recycled electrolyte containing about 36.5 percent HCl by weight. Both the fresh feed and the product reservoirs were initially charged with the dimethyl disulfide/hydrochloric acid mixture. The fresh feed mixture and the recycled electrolyte were each pumped at a flow-rate of 1.3 ml/min and combined just prior to entering the electrochemical cell.
• This example illustrates the production of ethanesulfonyl chloride by the electrolytic oxidation of diethyl disulfide according to the method of this invention.
• Example 3 The same electrolysis cell used in Example 3 was used except that both the anode and the cathode were constructed from graphite (POCO Graphite AXF-51-BG) and the inter-electrode gap was adjusted to 2 mm.
• the diethyl disulfide was pumped directly into the electrolysis chamber through a glass tube (3 mm diameter) with a sintered-glass frit on the end, which was inserted into the bottom of the electrolysis chamber through the TEFLON® frame of the cell, using a syringe pump at a flow-rate of 0.040 ml/min.
• Concentrated hydrochloric acid (37.1 percent HCl by weight) was charged to a reservoir consisting of a 1000 ml resin kettle equipped with a cooling jacket through which an aqueous ethylene glycol solution was circulated from a constant-temperature circulating cooling bath.
• the contents of this reservoir were cooled and maintained at a temperature of 5-8 degrees Centigrade and were circulated through the electrolysis cell and back to the reservoir at a flow-rate of 15.0 ml/min.
• the cell was operated at a current of 5.0-5.1 amperes at 4.5-4.9 volts DC.
• the temperature of the reaction mixture within the electrolysis chamber was 14-18 degrees Centigrade.
• the effluent from the cell was collected in the reservoir and recycled.
• This example illustrates the production of methanesulfonic acid from dimethyl disulfide according to the method of this invention.
• the plate-and-frame cell electrolysis apparatus described in Example 5 was used.
• the reservoir was charged with an aqueous solution containing 36 percent methanesulfonic acid by weight and 15 percent hydrogen chloride by weight and the reservoir was heated and maintained at a temperature of 72-76 degrees Centigrade.
• This aqueous solution was recirculated through the cell at a flow-rate of 18.0 ml/min and dimethyl disulfide was added directly to the electrolysis chamber of the cell at a flow-rate of 0.015 ml/min.
• a current of 2.5-2.6 amperes at 2.6-2.8 volts DC was passed through the cell and the temperature of the reaction mixture within the cell rose to 82-87 degrees Centigrade. Under these conditions methanesulfonic acid was produced in a yield of 90 percent with a current efficiency of over 99 percent.

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• Metallurgy (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 1988
  • 1988-12-29 IN IN1074/CAL/88A patent/IN170927B/en unknown
• 1989
  • 1989-01-05 DE DE8989100154T patent/DE68905638T2/de not_active Expired - Fee Related
  • 1989-01-05 EP EP89100154A patent/EP0331864B1/en not_active Expired - Lifetime
  • 1989-01-05 ES ES198989100154T patent/ES2039702T3/es not_active Expired - Lifetime
  • 1989-01-16 MX MX014555A patent/MX169944B/es unknown
  • 1989-03-03 BR BR898900993A patent/BR8900993A/pt not_active Application Discontinuation
  • 1989-03-06 DK DK106089A patent/DK106089A/da not_active Application Discontinuation
  • 1989-03-06 JP JP1052188A patent/JPH01272786A/ja active Pending

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