US3652430A

US3652430A - Electrolytic condensation of carboxylic acids

Info

Publication number: US3652430A
Application number: US774415A
Authority: US
Inventors: Fritz Beck; Walter Himmele; Juergen Haufe; Andreas Brunold
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1967-11-11
Filing date: 1968-11-08
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28
Also published as: DE1643693A1; CH506451A; NL6816045A; AT288346B; BE723694A; DE1643693B2; FR1591366A; DE1802865A1; GB1250212A

Abstract

Process for the electrochemical condensation of carboxylic acids by the electrolysis of monocarboxylic acids, half esters of dicarboxylic acids or aminocarboxylic acids in which current densities of more than 10 amp./dm.2 on vibrating electrode pairs are used, and in which the degree of neutralization of the carboxylic acids is kept below 10 percent, said process providing high space-time yields and a reaction product which can be worked up without difficulty.

Description

United States Patent Beck et al. [451 Mar. 2%, W72

[54] ELECTROLYTIC CONDENSATION OF CARBOXYLIC ACIDS [56] References Cited [72] Inventors: Fritz Beck, Ludwigshafen; Walter Him- FOREIGN PATENTS OR APPLICATIONS mele, Walldorf; Juergen Hauie, Lambsheim; Andreas Brunold, Lud- 355,403 11/1952 Germany wigshafen, all of Germany Primary Examiner-Daniel E. Wyman [73] Asslgnee: Badlsche Amnn" l l g Assistant Examiner-Philip M. French i ga Ludwlgshafen (Rvhmex Attorney-Johnston, O'Keeffe, Keil, Thompson & Shurtleff [22] Filed: Nov. 8, 1968 [57] ABSTRACT [21] Appl. No.: 774,415 Process for the electrochemical condensation of carboxylic acids by the electrolysis of monocarboxylic acids, half esters of dicarboxylic acids or aminocarboxylic acids in which cur- [30] Foreign Application Priority Dam rent densities of more than 10 amp./cim. on vibrating elec- Nov. 1 l, 1967 Germany ..P 16 43 693.4 trode pairs are used, and in which the degree of neutralization of the carboxylic acids is kept below 10 percent, said process US. Cl roviding spaceqime yields and a reaction product which 204/222 can be worked up without difficulty. 511 lm. Cl. ..B0ld 3/00 [58] Field of Search ..204/72, 221, 222, 223, 59 7 Claims, 3 Drawing Figures PATENTEnmze m2 3, 652.430

sum 2 UF 2 ul I FIG?) FIG. 2

INVENTORSI FRH'Z BECK WALTER HIMMELE JUERGEN HAUFE ANDREAS BRUNOLD ELECTROLYTIC CONDENSATION OF CARBOXYLIC ACIDS The invention relates to the electrolytic condensation of carboxylic acids which is known under the name Kolbe synthesis.

Electrolytic condensation of carboxylic acids is a method for reacting substituted or unsubstituted carboxylic acids with elimination of carbon dioxide according to the equation:

in which R denotes an alkyl radical which may bear carboxyalkyl groups or acylated amino groups as substituents. In the prior art methods a high current density may be used in which case a high degree of neutralization is required to achieve adequate cell voltages, i.e., a considerable proportion of the acid has to be neutralized prior to electrolysis so that the solution has adequate conductance. It is also possible to be content with a low degree of neutralization but then high current densities cannot be used. In the former case it is comparatively difficult to process the reaction mixture because a small amount of reaction product has to be separated from a large amount of salt. In the second case long reaction periods have to be accepted. These relationships are known from a number of publications, for example from Liebigs Annalen, 261, 107 et seq. (1891); Fette und Seifen, 57, 675 et seq. (1955), and 61, 1,124 et seq. (1959); Chemical Industry (U.S.S.R volume 1960, pages 359 et seq. and volume 1963, pages 263 et seq.; Journal of Applied Chemistry (U.S.S.R.), 35, 1082 et seq. (1962); Chemie-lngenieur-Technik, 37, 607 et seq. (1965); and U.S. Pat. No. 2,439,425. From these works it is clear that the use of methanol as solvent gives better yields of product and current than the use of water.

It is an object of this invention to provide a process for the electrochemical condensation of carboxylic acid in which (a) high yields and high space-time yields are obtained, (b) the current efficiency is high and (c) the working up of the reaction mixture is relatively simple.

This and other objects and advantages will be better understood from the following detailed description.

We have found that electrochemical condensation of organic carboxylic acids in electrolytic cells having pairs of vibrating electrodes can be carried out very advantageously and without the disadvantages of the prior art methods by keeping the degree of neutralization of the carboxylic acid at less than 10 percent and the current density at more than 10, preferably at from 25 to 50, amperes per square decimeter.

Degree of neutralization is defined as the molar proportion of the organic carboxylic acid which is neutralized with a base prior to electrolysis in order to achieve the necessary conductance in the electrolysis system.

It is surprising that it is possible by the process according to this invention to use not only high current densities but also low degrees of neutralization, a combination of conditions not hitherto thought to be possible. Decreasing the distance between the electrodes alone does not by any means achieve the result in this type of electrolysis because the space between the electrodes is filled to an increasing extent with gas bubbles so that the cell voltage increases again at small distances. Moreover the gas bubbles have a tendency to adhere to the surface of the electrodes. The advantages are evident. Yields and current efficiencies are very high, the space-time yield is clearly higher and working up is much simler. p The process is applicable in principle to all electrochemical condensations of carboxylic acids. Information regarding the breadth of application of the Kolbe synthesis is given in detail for example in Russian Chemical Reviews (English translation, 29, 161 to 180 (180). In addition to the electrolysis ofalkanecarboxylic acids, the electrolysis of hemiesters of alkanedicarboxylic acids and of aminoalkanecarboxylic acids is very important. It is expedient to subject to electrolysis carboxylic acids and their derivatives which contain from two to 12 carbon atoms in the acid radical. When hemiesters of dicarboxylic acids are to be electrolyzed it is preferred to use those of lower alcohols, particularly methyl or ethyl esters. In the case of aminocarboxylic acids those having protected amino groups, usually the acetylated compounds, are used. The process is particularly important for the production of diesters of sebacic acid from hemiesters of adipic acid, particularly the methyl or ethyl esters, and for the synthesis of N,N'- diacetyl-decamethylenediamine from epsilonacetylaminocaproic acid, of 1,10-dibromodecane from omega-bromocaproic acid and of octane-2,7-dione from lawlinic acid.

Electrochemical condensation is carried out using solvents, for example water, but preferably using nonaqueous solvents such as lower alcohols, for example those having one to four carbon atoms such as methanol, ethanol, ethylene glycol and isopropanol, or N,N-dialkylamides of lower alkanedicarboxylic acids, for example those having one to five carbon atoms whose alkyl radicals contain not more than three carbon atoms, particularly dimethylformamide, diethylformamide, dimethylacetamide or diethylacetamide, or using N-methylpyrrolidone, or a mixture of solvents with or without water. Generally 10 to 20 percent by weight solutions of the carboxylic acids to be electrolyzed are used.

The degree of neutralization is adjusted by adding bases prior to electrolysis. It is kept at less than 10 percent and preferably at only 2 to 5 percent. The bases used, depending on the solvent, may be aqueous alkalies such as caustic soda solution, caustic potash solution, sodium or potassium carethylate, sodium carbonate or potassium carbonate; in all cases, ammonia or bases having adequate basicity such as dimethylamine, trimethylamine, triethylamine or alkanolamines such as dimethylethanolamine or morpholine, may also be used.

The process is advantageously carried out in electrolytic cells having pairs of vibrating electrodes such as are described in detail for example in British Pat. application No. 30712/66.

These electrodes are liquid-permeable, for example in the form of netting, expanded metal or screens and are arranged opposite to each other at a very small distance of less than 1 mm,, preferably of from 0.1 to 0.3 mm. A layer of woven or non-woven glass fiber cloth, paper, polyamide cloth, polyester cloth, polyvinyl chloride cloth, polypropylene cloth or polytetrafluoroethylene cloth, which is permeable to liquid is provided between the electrodes as a spacer and insulator. The electrodes are held in position by suitable mechanical means made of alloy steel, titanium, aluminum (particularly anodized aluminum), polyvinyl chloride, polypropylene, polyethylene or glass. The pair of horizontal electrodes is preferably vibrated perpendicularly to their planes with a frequency of from 1 to 1,000 cycles per second and an amplitude of 0.3 to 2 mm.

Platinum, alloys of platinum and rhodium or of platinum and iridium, gold, alloys of gold and platinum, for example Au:Pt :10, platinized titanium or tantalum, or titanium or tantalum which'have been gilded, are suitable as the material for the anodes. The material for the cathodes is not critical; all that is necessary is that it should not corrode in the weakly acid electrolytes when no current is passing. Platinum, alloy steel, nickel or titanium are suitable. Platinum and nickel have the advantage of low hydrogen overvoltage.

The invention will now be described with reference to the drawings in which:

FIG. 1 is a sectional elevation of an electrolytic cell, and

FIGS. 2 and 3 illustrate embodiments of pairs of electrodes.

The electrolytic cell shown diagrammatically in FIG. 1 is a convenient embodiment given by way of example. It consists of an electrolysis vessel 1 provided with a cover 2. The electrolysis vessel contains a horizontal pair of electrodes consisting of a cathode netting 3 and an anode netting 4 which are kept apart from each other by a coarsely porous insulating material 5. The two nettings are pressed together by two wheel-shaped members 6 and 7 of suitable plastics which are secured at the lower end of the axis 8 of a vibrator. Contact is made with the nettings by

contacts

9 and 10 which in turn are connected with the vibrator axis 8 (sewing as an electric lead) and with a flexible lead 11. The vibrator axis 8 is carried by a vibrator 12 and is passed into the cell through a rubber membrane 13 which gives a gastight seal. The apparatus is also provided with a glass electrode 14, a thermometer 15, a dropping funnel l6 and an offgas pipe through a brine-cooled reflux condenser 17. The cell stands in a waterbath (not shown) through which tap water fiows for the purpose of cooling.

It is possible however, and may even be advantageous, to combine a liquid-permeable cathode of the said type with a liquid-permeable anode. It is very difficult to prepare liquidpermeable anodes having good resistance to corrosion if it is not desired to use anodes made wholly of precious metal which are too expensive for large scale manufacture. It is preferable to use composite electrodes, i.e., those consisting of a base metal, for example aluminum or an alloy thereof for example with l to 3 percent of magnesium, having a coating of precious metal, particularly of platinum. The layer of precious metal then need only be from about 3 to 70 microns in thickness. It is essential that the coating of precious metal is continuous. Parts which are not covered with precious metal may be covered with a plastics resin or paint which is insoluble in the reaction medium.

The pair of electrodes formed by anode, insulating layer and cathode may be disposed horizontally or vertically in the electrolytic cell and then in the reaction mixture. The pair of electrodes may be vibrated perpendicular or parallel to the macroscopic surface of the electrodes. Two possibilities are shown in FIGS. 2 and 3 which have proved to be particularly suitable. FIG. 2 illustrates a pair of electrodes which vibrates perpendicularly to the planes of the electrodes while FIG. 3 illustrates a pair of electrodes which vibrates parallel to the planes of the electrodes. The anode is a circular or square plate consisting of a base metal 18 covered on one side with a thin layer 19 of platinum. A liquid-permeable insulating layer and the liquidpermeable cathode 3 are placed on top of the anode. The sides of the base metal of the anode which are not covered by platinum are coated with plastics 20 to protect them from corrosion. The pair of electrodes is submerged in the reaction mixture contained in the electrode vessel 1. The axis 8 of the vibrator passes through the cover 2 of the electrolysic cell and is driven by the vibrator 12. The output of the apparatus may easily be increased by arranging two or more pairs of electrodes in series one above the other in an analogous manner as bipolar units. When the electrodes vibrate perpendicularly to the surface as in FIG. 2, the vibrator axis may serve at the same time for clamping together and as electric return lead. When the electrodes vibrate parallel to the surface (as in FIG. 3) separate bolts have to be passed through for clamping.

The current density may be set at a high figure in spite ofthe low degree of neutralization. Current densities of 25 to 50 amperes per square decimeter are immediately possible industri ally. Cell voltages of from 5 to 18, particularly from 8 to 12, volts are generally used.

The reaction temperature is usually kept at from 30 to 65 C. It has been found that in methanol solutions a flat minimum of the cell voltage occurs at 40 to 55 C.

Conversion of carboxylic acids may be very high, for example more than 90 percent, by reason of the low degree of neutralization, and this has an advantageous effect on the processing of the reaction mixture. The cell voltage declines during electrolysis although a relatively nonpolar product accumulates, whereas in conventional methods the cell voltage increases during electrolysis and the increase may exceed 100 percent ofthe original value.

The process may be carried out continuously at a high concentration of the electrolysis products and a low concentration of the acid to be electrolyzed without impairment of the yield. The anodic oxidation of the product thus plays no part, i.e., in spite of the low concentration of the starting materials these are preferentially reacted at the electrodes.

The working up the reaction mixture (illustrated later by way of example with reference to the synthesis of sebacic esters) is very simple. Countercurrent extraction with organic solvents, for example octane or cyclohexane, such as is necessary in the prior art methods, can be dispensed with. The solvent is advantageously distilled off from the reaction mixture in a falling film evaporator. The bottom contains a mixture of sebacic esters, unreacted hemiesters of adipic acid, precipitated salt of the hemiester and low boiling C monocarboxylic esters formed as byproducts (these are particularly methyl valerate, methyl allylacetate, methylw-alkoxyvalerates and methylw-hydroxyvalerate) and the salts and unreacted hemiesters may be separated therefrom by extraction with water. The sebacic esters and the byproducts remaining in the organic phase may be separated by distillation or by freezing out the sebacic ester and filtering it off. The mixture remaining after distilling off the residue may also be separated into its components by filtering off precipitated salts, freezing out the sebacic esters from the filtrate and separating by distillation the unreacted hemiesters of adipic acid and the byproducts.

The invention is illustrated by the following Examples.

EXAMPLE I In a glass electrolytic cell 1 as shown diagrammatically in FIG. 1 which is provided with a polyethylene cover 2 a horizontal pair of electrodes is mounted. This consists of a circular cathode netting 3 (nickel, 400 meshes per cm?) and an anode netting 4 of the same size made of an alloy of platinum and rhodium and having 1,024 meshes per cm. which are insulated from each other by a coarsely porous non-woven glass fiber fabric 5 having a thickness of 0.15 mm. The two nettings are pressed together by two wheel-shaped members 6 and 7 of polypropylene and are secured at the lower end of a vibrator axis 8. Contact with the nettings is provided by

contacts

9 and 10 which are connected with the electrical supply through the vibrator shaft 8 serving as an electrical conductor and a flexible lead 11. The vibrator shaft 8 is secured to a vibrator 12 (40 watts, 50 cycles per second) and passes into the cell 1 through a rubber membrane 13 which gives a gastight seal. The apparatus is also provided with a glass electrode 14, a thermometer 15, a dropping funnel 16 and an offgas outlet through a brine cooled reflux condenser 17. The cell stands in a bath (not shown) of flowing tap water to keep it cool.

At the beginning the electrolysis, 500 g. of a solution of 200 g. of monomethyl adipate (neutralized to the extent of 5 percent with a methanol solution of sodium methylate) in methanol is introduced into the cell. The vibrator is operated with an amplitude of l mm. and a frequency of cycles per second. Electrolysis is carried out at 10.0 amperes, i.e., a current density of 25 amperes per dm. with reference to the exposed area of netting of40 cm*. The temperature is kept at 42 C. The cell voltage at the beginning of the electrolysis is l4.8 volts, after 1 hour it is 14.3 volts, after 2 hours 13.9 volts, after 3 hours 12.7 volts and after 4 hours and 12 minutes (the end) 10.5 volts. During this period the pH value is raised from 5.1 to 7.0. The amount of current passed through corresponds to a conversion of 132 percent, with reference to the free hemiester.

To work up the reaction mixture it is freed from solvent in a rotary evaporator. The residue, made turbid by precipitated sodium salt, is diluted with hexane, washed with three times its amount of water and then freed from hexane in a rotary evaporator. The residue of I22 g. is shaken with a small amount of 8 percent sodium bicarbonate; l 19 g. of crude sebacic ester remains. 0.16 g. of hemiester is found in the aqueous phase by titration. Thus a total of about 3 g. of unreacted hemiester is determined. Gas chromatographic analysis gives a content of 92 percent of sebacic ester in the crude ester. This is a yield of8 l .8 percent and a current efficiency of 60.8 percent.

In the fractional distillation at l.0 mm./1 16 C. of a number of crude ester fractions, a pure sebacic ester is obtained (purity more than 99.6 percent) which crystallizes completely at room temperature. The amount agrees very well with the amount calculated from the individual gas chromatographic data.

EXAMPLE 2 Kolbe synthesis is carried out under the conditions specified in Example 1 but with the difference that the current density is varied. The results are collected in Table l in which V mean cell voltage; Y yield of dimethyl sebacate in percent; and CE current efficiency in percent.

Kolbe synthesis is carried out under the conditions specified in Example 1 but with the difference that the degree of neutralization is varied. The results are collected in Table 2:

TABLE 2 Degree of neutralization V Y CE EXAMPLE 4 Kolbe synthesis is carried out under the conditions specified in Example 1 but with the difference that the base with which the monomethyl adipate is neutralized is varied. The results are collected in Table 3:

TABLE 3 Base V Y CE sodium niethylate l 1.0 81.8 60.8 potassium methylate l 1.0 82.7 61.7 lithium methylate 15.8 83.8 62.2 ammonia 14.6 82.9 61.8 triethylamine 13 82.7 61.7 dimethylethanolamine 11.7 84.3 38.4 morpholine 19.5 85.0 65.7

EXAMPLE 5 Kolbe synthesis is carried out under the conditions specified in Example 1 but with the difference that the solvent is varied. The results obtained are collected in Table 4.

TABLE 4 Solvent V CE methanol 1 1.0 31.8 60.0 dlmethylformamide 20 85.9 76.11 dimethylformamide:methanol 1:1 14.9 83.3 65.0 isopropanolzmethanol 1:1 36 83.8 67.11 isopropanolzmethanol 1:1 21.6 82.0 63.5

EXAMPLE 6 333 g. of a mixture of 400 g. of monomethyl adipate, 587.4 g. of methanol and 12.6 g. of triethylamine is introduced into the electrolytic cell described in Example 1 at the beginning of electrolysis. 2 hours and 44 minutes later (i.e., after reaching a theoretical current conversion of 132 percent at 10 amperes and a current density of 25 amperes per cm?) further mixture is dripped in continuously at the rate of 2 grams per minute and an equivalent amount of reaction mixture is withdrawn. During this continuous period the cell voltage remains constant at 18.5 volts and the pH value at 6.8. Working up three fractions, each of 290 g., gives the following results:

Yield 70 Current efficiency k 15! fraction 80.0 56.5 2nd fraction 79.0 55 3rd fraction 81.5 57.

EXAMPLE 7 A mixture of 14 g. of monomethyl adipate, 73.5 g. of sebacic ester, 8.05 g. of 29.5 percent sodium methylate solution and 254.4 g. of methanol is introduced at the beginning of electrolysis in the electrolytic cell described in Example 1. This mixture corresponds to the mixture described in Example 1 after 95 percent conversion of the free hemiester with an 80 percent yield.

At 10 amperes (i.e., a current density of 25 amperes per cm?) 680 g. of a mixture of methanol and percent by weight of the hemiester of adipic acid with a degree of Y neutralization of cv= 5 percent is dripped in continuously over a period of 5 hours 40 minutes. The cell voltage is constant at 10.0 volts and the pH value is constant at 6.8. Working up the whole reaction mixture gives a yield of 81.2 percent and a current efficiency of 57.8 percent after deduction of the original sebacic ester.

EXAMPLE 8 Electrolysis is carried out under the conditions given in Example l in an electrolytic cell as described in Example 1 but in which a titanium wire netting having meshes per cm. which has been covered galvanically with a layer of platinum having a thickness of 4 microns is used as the anode. The cell voltage at the beginning of electrolysis is 16.8 volts, after 1 hour it is 15.0 volts, after 2 hours 14.0 volts, after 3 hours 12.5 volts and after 4 hours 12 minutes (the end) it is 11.0 volts. During this time the pH value rises from 5.1 to 7.2. The yield of sebacic ester is 82.2 percent and the current efficiency is 60.6 percent.

EXAMPLE 9 A vertical glass tube having an internal diameter of 100 mm. and a height of 1,000 mm. is used as the electrolytic cell. A Liebig condenser is arranged parallel to the tube and is connected with the tube by horizontal pipes at the top and bottom. Six pairs of electrodes (diameter 88 mm., spacing 100 mm.) are mounted on a vibrator shaft in the cell; the pairs of electrodes have the composition as described in Example 1. The pairs of electrodes are connected electrically in series by shaft sections of anodized aluminum coated with condensation lacquer.

At the beginning of electrolysis 9.67 kg. of the mixture described in Example 1 is introduced into the cell. A strong circulatory flow is set up in the reactor by the copious evolution of gas and thermosyphonic effect, without a special pump being necessary. The temperature can be kept at 50 C. by water cooling. Electrolysis is carried on at a current density of 25 amperes per dm After an initial period of 13.4 hours,

fresh reaction solution is metered in continuously at the rate of 715 g. per hour (786 ml. per hour) and the volume in the v reactor is kept constant by an overflow. The pH value remains constant at from 7 to 7.2. Electrolysis is continued for 300 hours. From samples taken daily it is found that a mean yield of 76 percent of the theory and a mean current efficiency of 54 percent of the theory are achieved. No change in these values can be detected with time. The mean cell voltage per pair of electrodes is 12 volts.

EXAMPLE 10 The pair of electrodes is as shown in FIG. 2 and consists of a horizontal circular base plate of aluminum 18 onto which is bonded a smooth platinum foil 19 having a thickness of 40 microns by means of a conducting synthetic resin adhesive. The sides of the base plate which are not covered with platinum are coated at 20 with a polyether containing chlorine such as is sold under the registered trade mark PENTON. The interlayer is a polyester cloth having 50 meshes per cm. The cathode 3 is an alloy steel netting having 100 meshes per cm. The interlayer and the cathode are pressed against the platinum anode by means of a propylene member shaped like a spoked wheel (not shown). The pair of electrodes is placed in an electrolytic vessel 1 of glass and is vibratedwith an electromagnetic vibrator 12; the vibrations are perpendicular to the surface of the electrodes and have an amplitude of 1 mm. and a frequency of 50 cp. At the beginning of electrolysis 400 g. of a solution of l60 g. of monomethyl adipate in methanol, which has been neutralized to the extent of 5 percent with sodium methylate, is placed in the cell. Electrolysis is carried on at amperes corresponding to a current density of 25 amperes per dm. and at a temperature of 42 C. 3 hours and 32 minutes later (corresponding to a theoretical current conversion of 132 percent) electrolysis is stopped. The cell voltage falls continually from 15.5 volts at the beginning to l 1.0 volts at the end. The reaction mixture is worked up to give a yield of dimethyl sebacate of 81.5 percent and a current efficiency of 60 percent. These voltages and yields substantially correspond to the values obtained under the same conditions with a double netting arrangement.

EXAMPLE 11 400 g. of a solution of 120 g. of mono-2-ethylhexyl adipate in methanol which has been neutralized to the extent of 10 percent with sodium methylate is placed in the electrolytic cell described in Example 10 at the beginning of electrolysis. Electrolysis is carried on at 8 amperes corresponding to a current density of amperes per dm. and at a temperature of 45 C. The vibrator operates at 50 cycles per second and an amplitude of 1.5 mm. After exactly 2 hours corresponding to a theoretical current conversion of 142 percent the electrolysis is stopped. During electrolysis the current is stopped for 10 seconds at intervals of 10 minutes. In this way the voltages vary within a fairly narrow range of from 15 to 17 volts. The voltage rises from the lower limit to the upper limit during an operational period. Working up the discharge from the electrolysis gives a yield of di-2-ethylhexyl sebacate of 71.6 percent and a current efficiency of 51 percent. These voltages and yields substantially correspond to the values obtained under the same conditions with a double netting arrangement.

EXAMPLE 12 As in FIG. 3, the pair of electrodes consists of a vertical square base plate of aluminum 18 to which a smooth foil 19 of platinum having a thickness of 60 microns is bonded on one side. The platinum foil is bent over the top edge of the base plate and at the upper narrow side contacts the vibrator shaft. The surface of the aluminum plate which is not covered by platinum is coated with chlorinated polyether. A polyester fabric having 50 meshes per cm. serves as interlayer 5 and a titanium netting with 13 meshes per cm. serves as cathode 3. Cathode and interlayer are pressed onto the anode by means of four bolts passing throughat the corners of the square.

Electrolysis 18 carried out in this cell with a reaction mixture and under the condition of Example l0, l0 amperes again corresponding to a current density of 25 amperes per dm. The cell voltage drops during electrolysis from 15 to 12 volts. Working up the reaction mixture gives a yield of 81 percent of dimethyl sebacate at a current efficiency of 60 percent. These values again correspond substantially to the values obtained under the same conditions with a double netting arrangement.

We claim:

1. A process for electrochemical condensation of an organic compound selected from the group consisting of alkanecarboxylic acids, hemiesters of alkanedicarboxylic acids and aminoalkanecarboxylic acids which comprises placing said organic compound in an electrolytic cell having vibrating pairs of electrodes and thereafter passing a current through said cell, said current having a density greater than 10 amperes per dmF, wherein the degree of neutralization of the organic com pound is less than 10 percent, and wherein the cell voltage is from 5 to 18.

2. A process as claimed in claim 1 wherein the current density is from 25 to 50 amperes per dm.

3. A process as claimed in claim 1 wherein a lower alcohol of the N,N-dialkylamide of a lower alkanecarboxylic acid, or a mixture of such compounds, is used as a solvent.

4. A process as claimed in claim 1 wherein a cathode which is permeable to liquid and an anode which is permeable to liquid are used.

5. A process as claimed in claim 1 wherein a cathode which is permeable to liquid and an anode which is not permeable to liquid are used.

6. A process as claimed in claim 5 wherein the anode is formed by a platinum foil or screen having a thickness of from 3 to 70 microns which is bonded by means of an electrically conducting adhesive to a flat base plate.

7. A process as claimed in claim 6 wherein the base plate is made of aluminum.

mg?" UNITED STATES PATENT OFFICE CERTIFICATE OF

QORRECTFUN

3, 52, 5 Dated March 28, 1972 Patent No.

Inventofls) Fritz Beck et a1 It is certified that: error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

First page, left-hand column, twentieth line, insert 12, 0 a I 0 JP ""0 Signed and sealed this 21st day of November 1972.

(SEAL) Attast:

EDWARD MQFIQETCHE R ,JR. ROBERT GOTISCHALK Attesting Officer Commissioner of Patents

Claims

2. A process as claimed in claim 1 wherein the current density is from 25 to 50 amperes per dm2.
3. A process as claimed in claim 1 wherein a lower alcohol of the N,N-dialkylamIde of a lower alkanecarboxylic acid, or a mixture of such compounds, is used as a solvent.
4. A process as claimed in claim 1 wherein a cathode which is permeable to liquid and an anode which is permeable to liquid are used.
5. A process as claimed in claim 1 wherein a cathode which is permeable to liquid and an anode which is not permeable to liquid are used.
6. A process as claimed in claim 5 wherein the anode is formed by a platinum foil or screen having a thickness of from 3 to 70 microns which is bonded by means of an electrically conducting adhesive to a flat base plate.
7. A process as claimed in claim 6 wherein the base plate is made of aluminum.
18.