US3193478A - Electrolytic coupling of olefinic compounds - Google Patents

Description

United States Patent 3,193,478 ELECTROLYTIQ COUPLING 0F OLEFINIC CQMROUNDS Manuel M. Baizer, St. Louis, Mo., assignor to Monsanto Company, a corporation of Delaware No Drawing. Filed Aug. 13, 1962, Ser. No. 216,305 7 Claims. (Cl. 204-723) H R R H Where X and Y are selected from the group consisting of cyano, carboxylate, and carboxamido groups, and R and R can, for example, be hydrogen or alkyl (including cycloalky-l) radicals, particularly such radical-s containing no more than eight carbon atoms; while R is a hydrocarbon radical so that a hydrocarbyloxy radical is attached to the beta-carbon atom of the alpha,beta-olefinic carboxy-lates, nitriles and amides, the hydrocarbyloxy radicals preferably having no aliphatic unsaturation and generally being monocyclic or acyclic groups of up to 20 carbon atoms, or often no more than 10 carbon atoms, such as alkyl, aralkyl, etc. Each individual R, R and R" can be the same as or difierent from another R, R or R, and X and Y can be the same or different. However, the present invention is primarily concerned with hydrodimerizations, i.e., reductive couplings in which the two reactant compounds to be coupled are the same. X and Y can be further defined as representing:

-CN, -c'i-Nrn or ('i-OR in which R represents hydrogen or hydrocarbon radicals, e.g., alkyl radicals, and R represents hydrocarbon radicals, e.g., alkyl or aryl radical, particularly such radicals containing no more than eight carbon atoms.

Compounds suitable as reactants in the present invention are illustrated, for example, by the above formulae in which X and Y can be cyano, carboxamido, N,N-diethylcarboxamido, carbethoxy, carbhexoxy, carbphenoxy, etc., radicals, and R" can be methyl, ethyl, propyl, isopropyl, isobutyl, hexyl, octyl, decyl, benzyl, etc., while R and R are hydrogen, methyl, ethyl, etc; Various combinations of substituents are suitable, as, :for example, in such compounds as ethyl, bet-a-ethoxyacrylate, beta-ethoxyacrylonitrile, beta-ethoxyacrylamide, beta-ethoxy-N, N-diethylacrylarnide, beta-hexyloxyacrylonitrile, betaoctyloxymethacrylonitrile, octyl beta-ethoxyacrylate.

In general, the electrolytic reductive coupling of the present invention is conducted in concentrated solution in an aqueous electrolyte. It is desirable to employ fairly concentrated solutions in order to minimize undesired reactions of intermediate ions with the water of the electrolyte. The olefinic reactants will ordinarily comprise at least about 10% by weight of the electrolyte, and preferably at least 20% by Weight or more. It is generally desirable to employ fairly high concentrations of salts in the electrolyte, for example constituting and usually 30% or more by Weight of the total amount of salt ice and water in the electrolyte, in order to obtain the desired solubility of the olefin-ic compounds.

The hydrodimerization of alpha,beta-olefinic carboxylates, nitriles and ca'rboxamides is taught in my copending applications S.N. 145,480 and 145,482, filed October 16, 1961, both of which are now abandoned, and S.N. 75,130, filed December 12, 1960, now forfeited, the disclosures of which are incorporated herein by reference; continuation-impart applications of the foregoing are S.N. 333,647, filed December 26, 1963, S.N. 337,540, filed January 14, 1964, and S.N. 337,546, filed January 14, 1964. The conditions taught in the referred-to applications for hydrodimerization are suitable for hydrodimerizations or other reductive couplings of the present invention.

Electrolysis, of course, has been practiced for many years and numerous materials suitable as electrolytes are 'known, making it within the skill of those in the art in the light of the present disclosure to select electrolytes for reductive coupling according to the present invention. As discussed in my aforesaid copending applications, some olefinic compounds are subject to polymerization or other side reactions if the electrolyte is acidic, or excessively alkaline, and it will be necessary in such cases to conduct the reductive coupling in solutions which are not overly acidic and also in some cases below a pH at which undesirable side reactions occur, e.g., below about 12. To minimize polymerization, simple reduction of the olefinic bond and other side reactions, the

pH is usually maintained in the range of about 3 to about 12, preferably 6 to 9.5.

When the catholyte during electrolysis is acidic, it will generally be advisable to conduct the electrolysis under conditions which inhibit polymerization of the reactants involved or in the presence of a polymerization inhibitor, for example, in an atmosphere containing sufiicient oxygen to inhibit the polymerization in question, or in the presence of inhibitors effective for inhibiting free radical polymerization. Classes of inhibitors for inhibiting free radical polymerizations are Well known, e.g., such inhibitors as hydroquinone, p,t-butyl catechol, quinone, pnitrosodimethylaniline, di-t-butyl hydroquinone, 2,5-dihydroxy-1,4-benzoquinone, 1,4-naphthoquinone, chloranil, 9,10-phenanthraquinone, 4-arnino-1-naphthol, etc., are suitable.

In etfecting the reductive coupling of the present in-' vention it is preferred to utilize a cathode having an overvoltage greater than that of copper and to subject to electrolysis in contact with such cathode a concentrated solution of a mixture of the defined olefinic compounds in an aqueous electrolyte under mildly alkaline conditions. In

effecting the reductive couplings of the present invention,

it is essential to obtain cathode potentials required for such couplings and therefore the salt employed should not contain cations which are discharged at numerically lower, i.e., less negative, cathode-potentials, but rather the electrolyte .should have a half-Wave potential substantially more negative than that at which the desired dirne-rization occurs. It is desirable that the salt employed have a high degree of water solubility to permit use of very concentrated solutions, for concentrated salt solutions dissolve greater amounts of the organic olefinic,

membrane is used, it is desir-able to avoid'types of anions which, in contact with hydrogen ions present in the anolyte chamber, would form insoluble acids and clog thepores of the membrane. Alternatively'the use of an ion exchange membrane effectively separates catholyte and anolyte and the use of different anions in the two chambers may minimize any difiiculties a particular anion would cause in one of the chambers.

In general amine and quaternary ammonium saltsare suitable for use in the present process. Certain salts of alkali and alkaline earth metalscan also be employed to some extent, although they are more subject to interfering discharge at the cathode and the alkaline earth metal salts use inadvisable.

As noted above, the present invention is primarily concerned with reductive coupling. of two molecules of the samecompound, i.e., with hydrodimerization. However, it also includes reductive couplings of beta-hydrocarbyl-oxy acrylates, nitr-iles or ac-rylamides with other compounds, e.g., with other beta-hyd-rocarbyloxy acr'yla-tes, nitriles or acrylamides, or with other hydrodimerizable olefinic compounds, for example with the alpha,beta-olefinic carboxylates, nitriles and amides taught in my aforesaid copending applications. The procedures set forth in my copending application S.N.Q163,028, filed December 29, 1961, can be employedwhen it is desired to direct the process to production of reduced, coupled products of two different compounds; for example, by regulating the cell voltage so that electrolysis occurs at a cathode potential close to that requiring the lowest voltage, i.e., the least negative voltage, particularly if the voltage for the more easily reducible monomer is 0.3 vol-t below that for the other monomer; and it is possible to minimize, hydrodimerization .of the. more easily reducible monomer by swamping the mixture with the other monomer, em

ploying only enough of the easily reducible monomer to keep the cathode potential at a value near that for reduction of the easily reducible monomer.

The process of the present invention produces novel compounds, such as illustrated by the formula of the prodnot in the illustration of the reaction hereinabove. The 3,4-dialkoxy adipates are of particular interest, as illustr-ated e in which each R can be alkyl or aryl, e.g., ethyl, methyl,

propyl, butyl, hexyl, octyl, phenyl, hexadecyl or various other radicals up to 20 or more carbon atoms, and each R can be alkyl, for example, any of the foregoing alkyl radicals.

Example 7 A catholyte was prepared by dissolving 91 grams ethyl beta-ethoxyacrylate in 91 grams of an 80% solution of tetraethyl-ammonium p-toluenesulfonate in water and 66 grams dimethylformamide. As anolyte, the 80% toluenesulfonate solution was used in an Alundum cup. The anode was platinum, and the cathode was 110 mL mer cury. The electrolysis was conducted with current of 2 to 3 amperes/SS cm. for about two hours for a total of about 6.3 ampere-hours. The cathode potential was 2.23 volts (vs. saturated calomel electrode). During the electrolysis, 2.5 ml. of acetic acid was added to the catholyte as necessary to prevent development of excess alkalinity. The catholyte was then extracted with methylene dichloride and the extract back-washed with Water, dried over calcium sulfate, and stripped of methylene dichloride to leave 115 grams residue which was stripped of volatilev material with Water pump vacuum to leave 28.6 grams liquid which was then distilled at 130142/5 mrrL, 11 1.4302. 7

. bases.

r 4 7 Analysis for diethyl 3,4-diethyoxyadipate: Calcd., C, 57.91; H, 9.03. Found, C, 58.43, H, 9.17.

The above example is illustrative of the present process and the reductive couplings of the various other olefinic reactants described herein can be conducted under the same conditions or numerous variations thereof. In ad dition, the procedures of the various examples of my aforesaid copending applications S.N. 145,480 and 145,482are applicable to the hydrodimerizations of the olefinic reactants described herein.

The electrolytic reductive couplings of the present invention are conducted in solution in electrolyte, generally in fairly concentrated solution in an aqueous electrolyte. It will be recognized that as used herein an electrolyte is considered aqueous even if the amount of water issrnall. Many electrolytes can be employed in the present invention but some are less suitable than others. The salts employed, either to provide conductivity or to increase solubility of the reactants have an important bearing on the electrolysis and will be discussed at length below. The acidity or basicity is also significant, neutral or mildly alkaline solutions generally being preferred. Many of the olefinic compounds employed in the present invention tend to polymerize when electrolyzed instrongly acidic solution, such as solutions of mineral acids, and it is desirable or necessary in such cases to avoid excessive acidity, making it desirable to operate at pHs above about 5 or 6, such as provided by solutions of salts of strong charge potential of about -1.5 volts, making it desirable to avoid high concentrations of hydrogen ion in the catholyte if the reductive coupling occurs at similar or more negative cathode potentials. The reductive couplings can suitably be conducted at pHs higher than those at which substantial polymerization of olefinic compound occurs, or higher than pHs at which there is undue generation of hydrogen, for example pHs at which more than half the currentis expended in discharging hydrogen ions. The pHs referred to are those obtaining in the bulk of the catholyte solution, such as determinable by a pH meter on a sample of the catholyte removed from the cell. The

. electrolysis in effect generates acid at the anode and base a tent the effects of acidity can be counteracted by high cur- OCCUI'S.

rent density to cause more rapid generation of hydroxyl ions. However, high current densities also require good stirring or turbulence to move the reactants to the cathode.

During electrolysis in-a divided cell, alkalinity increases in the catholyte. However, the anolyte becomes acidic. When a porous diaphragm is used to separate the catholyte from the anolyte, the alkalinity of the catholyte will depend upon the rate of diffusion of acid from the anolyte through the porous barrier. Control of alkalinity in the catholyte, when employing a diaphragm, may thus be realized by purposely leaking acid from the anolyte into the catholyte It can also be achieved, of course, by extraneous addition to the catholyte of an acid material, e.g., glacial acetic acid, phosphoric acid or p-toluenesulfonic acid. Alkalinity may also 'be controlled, whether or not a diaphragm is used in the cell, by employing buffer systems of cations which will maintain the pH range while not reacting at the reaction conditions.

When the olefinic compounds include a vcarboxylate, the pH of the catholyte solution should not be allowed to rise to the point where substantial hydrolysis of the ester Since the lower alkylesters, i.e., the methyl or ethyl esters, are usually more readily hydrolyzed than the higher alkyl esters, the optimum pH will vary with the nature of the ,ester. When the desired reaction involves Moreover, the hydrogen ion has a cathode dis 7 below 9.5. Otherwise, substantial quantities of bis(betacyanoethyDether are obtained. Similarly, when other olefinic nitriles are employed, it will be necessary to maintain the pH low enough to substantially minimize addition of water to the double bond. Good agitation or turbulence may counteract excess alkalinity to some extent, by minimizing local concentrations of hydroxyl ions at the cathode.

When a divided cell is employed, it will often be desirable to use an acid as the anolyte, any acid being suitable, particularly dilute mineral acids such as sulfuric or phosphoric acid. Hydrochloric acid can be employed but would have the disadvantage of generating chlorine at the anode, and being more corrosive with respect to some anode materials. When an acid is employed as anolyte, it is advantageous to use an ion exchange membrane to separate the anolyte from the catholyte. If desired, a salt solution can be used as anolyte, those useful as catholyte also being suitable as anolyte, although there are many other salt solutions suitable for such use.

Materials suitable for constructing the electrolysis cell employed in the present process are well known to those skilled in the art. The electrodes can be of any suitable cathode and anode material. The anode may be of virtually any conductor, although it will usually be advantageous to employ those that are relatively inert or attacked or corroded only slowly by the electrolytes; suitable anodes are, for example, platinum, carbon, gold, nickel, nickel silicide, Duriron, lead and lead-antimony and lead-copper alloys, and alloys of various of the foregoing and other metals.

Any suitable material can be employed as cathode, various metals and alloys being known to the art. It is generally advantageous to employ metals of fairly high hydrogen overvoltage in order to promote current efficiency and minimize generation of hydrogen during the electrolysis. In general it will be desirable to employ cathodes having overvoltages at least about as great as that of copper, as determined in a 2 N sulfuric acid solution at current density of 1 milliamp/square centimeter (Carman, Chemical Constitution and Properties of Engineering Materials, Edward Arnold and Co., London, 1949, page 290). Suitable electrode materials include, for example, mercury, cadmium, tin, zinc, bismuth, lead, graphite, aluminum, nickel, etc., in general those of higher overvoltage being preferred. It Will be realized that overvoltage can vary with the type of surface and prior history of the metal as well as with other factors; therefore the term overvoltage as used herein with respect to copper as a gauge has reference to the overv-oltage under the conditions of use in electrolysis.

Among the salts which can be employed according to the invention for obtaining the desired concentration of dissolved olefinic compound, the amine and quaternary ammonium salts are generally suitable, especially those of sulfonic and alkyl sulfuric acids. Such salts can be the saturated aliphatic amine salts or heterocyclic amine salts, e.g., the mono-, dior trialkylamine salts, or the mono-, dior trialkanolamine salts, or the piperidine, pyrrolidine or morpholine salts, e.g., the ethylaminc, dimethylamine or triisopropylamine salts of various acids, especially various sulfonic acids. Especially preferred are aliphatic and heterocyclic quaternary ammonium salts, i.e., the tetraalkylammonium or the tetraalkanolammonium salts or mixed alkyl alkanol ammonium salts such as the alkyltrialkanolammonium, the dialkyldialkanolammonium, the alkanotrialkylammonium or the N-heterocyclic N-alkyl ammonium salts of sulfonic or other suitable acids. The saturated aliphatic or heterocyclic quaternary ammonium cations in general have suitably high cathode discharge potentials for use in the present invention and readily form salts having suitably high Water solubility with anions suitable for use in the electrolytes employed in the present invention. The saturated, aliphatic or heterocyclic quaternary ammonium salts are therefore in general well adapted to, dissolving high amounts of olefinic compounds in their aqueous solutions and to efiecting reductive couplings of such olefinic compounds. It is understood, of course, that it is undesirable that the ammonium groups contain any reactive groups which might interfere to some extent with the reductive coupling reaction. In this connection it should be noted that aromatic unsaturation as such does not interfere as benzyl substituted ammonium cations can be employed (as also can aryl sulfonate anions).

Among the anions useful in the electrolytes, the aryl and alkaryl sulfonic acids are especially suitable, for example, salts of the following acids: benzenesulfonic acid, o, mor p-toluenesulfonic acid, 0-, mor p-ethylbenzenesulfonic acid, o, mor p-cumenesulfonic acid, o, mor p-tert-amylbenzenesulfonic acid, o, mor p-hexylbenzenesulfonic acid, o-xylene-4-sulfonic acid, p-xylene-Z-sulfonic acid, m-xylene-4 or 5 sulfonic acid, mesitylene-Z-sulfonic acid, durene-3-sulfonic acid, pentamethylbenzenesulfonic acid, o-dipropylbenzene-4-sulfonic acid, alphaor betanaphthalenesulfonic acid, o, mor p-biphenylsulfonic acid, and alpha-methyl-beta-naphthalenesulfonic acid. Alkali metal salts are useful in the present invention with certain limitations, and the alkali metal salts of such sulfonic acids can be employed, i.e., the sodium, potassium, lithium, cesium or rubidium salts such as sodium benzenesulfonate, potassium p-toluenesulfonate, lithium o-biphenylsulfonate, rubidium beta-naphthalenesulfonate, cesium p-ethylbenzenesulfonate, sodium o-xylene-3-sulfonate, or potassium pentamethylbenzenesulfonate. The salts of such sulfonic acids may also be the sautrated, aliphatic amine or heterocyclic amine salts, e.g., the mono-, dior trialkylamine salts, or the mono-, dior trialkanolamine salts, or the piperidine, pyrrolidine, or morpholine salts, e.g., the ethylamine, dimethylamine or triisopropylamine salt of benzenesulfonic acid or of o, por m-toluenesulfonic acid; the isopropanolamine, dibutanolamine or triethanolamine salt of o, por m-toluenesulfonic acid or of o, por m-biphenylsulfonic acid, the piperidine salt of alphaor beta-naphthalenesulfonic acid or of the cumenesulfonic acids; the pyrrolidine salt of o, mor pamylbenzenesulfonate; the morpholine salt of benzenesulfonic acid, of o, mor p-toluenesulfonic acid, or of alphaor beta-naphthalenesulfonic acid, etc. In general, the sulfonates of any of the ammonium cations disclosed generically or specifically herein can be employed in the present invention. The aliphatic sulfonates are prepared by reaction of the correspondingly substituted ammonium hydroxide with the sulfonic acid or with an acyl halide thereof. For example, by reaction of a sulfonic acid such as p-toluenesulfonic acid with a tetraalkylammonium hydroxide such as tetraethylammonium hydroxide there is obtained tetraethylammonium p-toluenesulfonate, use of which in the presently provided process has been found to give very good results. Other presently useful quaternary ammonium sulfonates are, e.g., tetraethylammonium 0- or m-toluenesulfonate or benzenesulfonate; tetraethylammonium o, mor p-cumenesulfonate or o, mor p-ethylbenzenesulfonate, tetramethylammonium benzenesulfonate, or o, mor p-toluenesulfonate; N,N-di-methylpiperidinium o, mor p-toluenesulfonate or o, mor pbiphenylsulfonate; tetrabutylammonium alphaor betanaphthalenesulfonate or o, mor p-toluenesulfonate; tetrapropylammonium o, mor p-amylbenzenesulfonate or alpha-ethyl-beta-naphthalenesulfonate; tetraethanolammonium o, mor p-cumenesulfonate or o, mor p-toluenesulfonate; tetrabutanolammonium benzenesulfonate or pxylene-3-sulfonate; tetrapentylammonium o, mor p-toluenesulfonate or o, mor p-hexylbenzenesulfonate, tetrapentanolammonium p-cymene-3-sulfonate or benzenesulfonate; methyltriethylammonium o, mor p-toluenesulfohate or mesitylene-Z-sulfonate; trimethylethylammonium o-xylene-4-sulfonate or o, mor p-toluenesulfonate; triethylpentylammonium alphaor beta-naphthalenesulfonate or o-, mor p-butylbenzenesulfonate, trimethylethanium.

troiyses in the tetraalkylamrnonium sulfonates are 6XClll-,

sively electrochemical processes. Among the ammonium and amine sulfonates useful as electrolytes in the present invention are the alkyl, ara'lkyl,

and heterocyclic amine and'arnmonium sulfonates, in Which ordinarily the individual substituents on the IlltI'O gen atom contain no more than atoms, and usually the amine or ammonium radical contains from 3 to carbon atoms. it will be understood, of course, that diand poly-amines and dland poly-ammonium radicals are operable and included by the terms amine and ammo- The sulfonate radical can be from aryl, alkyl, alkaryl or aralkyl' sulfonic acids of various molecular weights up to for example" 20 carbon atoms, preferably about 6 to 20 carbon atoms, and can include one, two

or more sulfonate groups. Any of the quaternary ammonium sulfonates disclosed and claimed in my copending group, e.g by sodium and alcohol or by hydrogenation, and the. resulting di-hydrocarbyloxyhexamethylene diamine can be reacted with polycarboxylic acids, e.g., adipic acid, to obtain hydrocarbyloxy-substituted polyamide. ,The dihydrocarbyloxy' adipamides can be reduced to amines or hydrolyzed to acids and converted into polyamides or polyesters in similar manner.

application S.N. 75,123, filed December 12, 1960, can a suitably be employed.

Another especially suitable class of salts for use in the present invention are .the alkylsulfate salts such as methosulfate salts, particularly the amine and quaternary ammonium methosuifate salts. Methosulfate salts such as the methyltriethylammonium, tri-n-propylmethylammonium, triamylmethylamrnonium, tri-n-butylmethylammonium, etc., are very hygroscopic, and the tri-n-butylmethylammoniurn in particular forms very concentrated aqueous solutions which dissolve large amounts of organic materials. suitable for use in the alkylsulfate salts are the same as those for the sulfonates. i

Various other cations are suitable for use in the present invention, e.g.',' tetraalkylphosphonium and trialkylsulfonium 'cations, particularly as sulfonate salts formed from sulfonic acids as described above, or as methosulfate salts.

The 3,4-bis(hydrocarbyloxy)adipates can be employed as lubricants or functional fluids and also serve as intermediates suitable for conversion to various reactive compounds or to polymers suitable for molding, coating, fiber-forming or other purposes. The adipa-tes can be hydrolyzed, e.g., by aqueous alkali, to dialkoxyadipic acids which can be reacted with polyhydric alcohols, e.g., ethylene glycol, to prepare alkoxy-substituted poly- In general the amine andammonium cations What is claimed is:

1. The method of producing a reduced, coupled product which comprises subjecting a solution of olefinic compound selected from the group consisting of betahydrocarbyloxy acrylic acid esters, beta-hydrocarbyloxyacrylamides' and beta-hydrocarbyloxyacrylonitriles to electrolysis in a'cell in which both anode and cathode are in actual physical contact with electrolysis medium,

.the solution being in contact with a cathode having a hydrogen ov'ervoltage greater than that of copper and containing water, at least about 10% by weight of olefinic compound and at least 5% by weight of salt to make the solution conductive and separating the reduced, coupled product from the solution.

2. The'method of claim 1 in which a beta-hydrocarbyloxy acrylic acid ester is hydrodimerized.

3. The method of claim 1 in which the solution comprises a salt selected from the group consisting of amine and ammonium sulfonates and alkyl sulfates.

4-. T he method of hydrodimerization which comprises subjecting an aqueous solution of olefinic compound selected from the group consisting of beta-hydrocarbyloxy acrylic acid esters, beta-hydrocarbyloxyacrylamides and beta-hydrocarbyloxyacrylonitriles to electrolysis in a cell in which both anode and cathode are in actual physical contact with electrolysis medium, the solution being in contact with a cathode having a hydrogen overvoltage greater than that of copper, causing development of the cathode potential required for hydrodimerization, the solution containing at least about 10% by weight of olefinic compound and at least 5% by weight salt which esters; or which can be reacted with polyamines, e.g.,

hexamethylene diamine to prepare alkoxy-substituted polyamides. If desired, the dihydrocarbyloxy adipates can be hydrolyzed under acidic conditions to cause selfcondensation of the resulting dihydroxy adipic acid to a polyester. The bis(hydrocarbyloxy)adiponitriles can be hydrolyzed to the acids in a manner similar to the adipates, 6

and then converted to the polyesters or polyamides. Or, if desired,"the nitrile group can be reduced to an amino References Cited by the Examiner UNITED STATES PATENTS 2,632,729' 3/53 Woodman 204-72 2,726,204 12/55 Park et al. 20472 2,921,089 l/ Hagemeyer et al 260475 2,957,022 10/60 Cohen 26O468 FOREIGN PATENTS 565,274 11/58 Canada.

JOHN H. MACK, Primary Examiner.

MURRAY TILLMAN, WINSTONA. DOUGLAS,

. Examiners.

hat-

Claims (1)

1. THE METHOD OF PRODUCING A REDUCED, COUPLED PRODUCT WHICH COMPRISES SUBJECTING A SOLUTION OF OLEFINIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF BETAHYDROCARBYLOXY ACRYLIC ACID ESTERS, BETA-HYDROCARBYLOXYACRYLAMIDES AND BETA-HYDROCARBYLOXYACRYLONITRILES TO ELECTROLYSIS IN A CELL IN WHICH BOTH ANODE AND CATHODE ARE IN ACTUAL PHYSICAL CONTACT WITH ELECTROLYSIS MEDIUM, THE SOLUTION BEING IN CONTACT WITH A CATHODE HAVING A HYDROGEN OVERVOLTAGE GREATER THAN THAT OF COPPER AND CONTAINING WATER, AT LEAST ABOUT 10% BY WEIGHT OF OLEFINIC COMPOUND AND AT LEAST 5% BY WEIGHT OF SALT TO MAKE THE SOLUTION CONDUCTIVE AND SEPARATING THE REDUCED, COUPLED PRODUCT FROM THE SOLUTION.