Hoechst Aktiengesellschaft

Steffen Dapperheld

Rudolf Heumuller

Manfred Wildt

Rudolf Rossmeissl

Werner Schwertfeger

Heinrich Volk

Heinz Litterer

Peter Wegener

Bernd Scharbert

Michael Feldhues

Gerhard Ullmann

Frank P Sistig

Pierre Babusiaux

Werner Lindner

Hans Milluwe

Klaus Kretschmann

Hans-Karl W Vom Baur, Deceased

Karl Peter

Electrochemical process for preparing glyoxylic acid

A process for the preparation of a 2-aminobenzothiazol of the formula ( I ) ##STR1## in which R.sub.1 and R.sub.2 independently of each other are hydrogen, fluorine, chlorine, bromine or iodine, trifluoromethyl or C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy or nitro groups, by conversion of an arylthiourea of the formula (II) in which R.sub.1 and R.sub.2 have the meaning mentioned, which comprises carrying out the conversion in 99 to 100% strength of sulfuric acid with continuous addition of catalytic amounts of bromine, hydrogen bromide or bromide in the form of aqueous solutions and using an arylthiourea of the formula (II) which contains 1 to 35% water.

Process for the preparation of 2-aminobenzothiazoles

Trichloroacetic and dichloroacetic acid are dehalogenated to give monochloroacetic acid by electrolyzing aqueous solutions of these acids in divided electrolysis cells using carbon cathodes; the aqueous electrolytic solutions also contain one or more metal salts having a hydrogen overvoltage of at least 0.4 volt (at a current density of at least 4000 A/m.sup.2) and specific ammonium and/or phosphonium salts. In this process, there is an extremely small evolution of hydrogen at the cathode, even at a very low concentration of the polychlorinated acetic acid, without the high selectivity of conversion of the electrolysis being impaired in continuous operation.

Partial electrolytic dehalogenation of dichloroacetic and

In the electrode in the form of a rectangular parallelepiped composed of impregnated graphite material for electrochemical reactors, the electrode (4,5) is provided with openings (8,9,10,11) extending perpendicular to its active electrode surfaces (6,7) at its corners. Canals (12,13) which extend parallel to the active electrode surfaces (6,7) in the direction of an adjacent opening (9,10) originates in each case from two openings (8,10) situated diagonally opposite each other. The canals (12,13) have communicating channels (14,15) to the active electrode surfaces (6,7).

Electrode for electrochemical reactors

In the preparation processes known hitherto for haloacrylic acids and deuterated derivatives thereof, it is necessary to use chemicals, some of which are very toxic or very expensive. However, fluoroacrylic acids are successively prepared from halogenated fluoropropionic acids and derivatives thereof by electrochemical elimination of halogen atoms. For this purpose, the acids or derivatives thereof are electrolyzed in a water-containing solution at a temperature from -10.degree. C. to the boiling point of the electrolysis liquid.

Process for the preparation of fluorinated acrylic acids and derivatives

Selectively dehalogenated thiophene derivatives are obtained from compounds of the formula II ##STR1## by an electrochemical reaction in a divided electrolysis cell in the presence of a suitable solvent, an onium compound or a compound which is converted into an onium compound in the electrolyte, and a conducting salt. Thiophene derivatives are important intermediates in the production of pharmaceuticals and plant protection agents.

Process for the preparation of thiophene derivatives

Process for the preparation of unsaturated halogenated hydrocarbons of the formula R.sup.1 --CR.sup.2 .dbd.CR.sup.2 --R.sup.2 in which R.sup.1 and R.sup.2 independently of one another are hydrogen, chlorine or fluorine, R.sup.2 is also --C(R.sup.1).sub.2 --R.sup.3 or the grouping [C(R.sup.1).sub.2 ].sub.m --C(R.sup.1).sub.2 represents two of the radicals R.sup.2, by electrolysis in the presence of certain onium compounds and metal salts, the electrolysis cells being divided or undivided. The process can be carried out continuously or discontinuously under atmospheric pressure or under an elevated pressure up to 10 bar and at temperatures from -40.degree. C. up to the boiling point of the electrolyte; the current density is in the range from 1 to 600 mA/cm.sup.2. The cathode is generally composed of carbon material. The products obtained are suitable for use as starting materials for the preparation of polymers containing fluorine.

Process for the preparation of unsaturated halogenated hydrocabons

A process for the preparation of fluoromalonic acid and derivatives thereof having the formula ##STR1## wherein R.sup.2 and R.sup.3 are equal or different and represent hydroxyl, the group OX, wherein X represents an alkali metal, alkaline earth metal or NH.sub.4.sup.+ ion or a C.sub.1 -C.sub.12 -alkyl group, or represent the group NR.sup.4 R.sup.5, wherein R.sup.4 and R.sup.5 are equal or different and are hydrogen or a hydrocarbon group of 1 to 12 carbon atoms, which comprises subjecting a compound of the formula ##STR2## wherein R.sup.1 is halogen of an atomic weight in the range from 35 to 127 and R.sup.2 and R.sup.3 have the meaning indicated above, to an electrolysis in an electrolyte liquid consisting of water, an organic solvent or a mixture thereof, at a temperature in the range of from - 20.degree. C. to the boiling temperature of the electrolyte, at a current density in the range of from 1 to 600 mA/cm.sup.2 at a cathode consisting of lead, cadmium, zinc, copper, tin, zirconium, mercury, alloys of at least 2 of these metals or of carbon.

Process for the preparation of fluoromalonic acid and its derivatives

The invention relates to a process for preparing compounds of the formula

Process for preparing fluorinated vinyl ethers

The existing processes for the preparation of halogenoacrylic acids and deuterated derivatives thereof have to be carried out using chemicals which are in some cases very toxic or very expensive. Electrochemical reduction, however, makes it possible to eliminate one or more halogen atoms selectively from halogenoacrylic and halogenomethacrylic acids and derivatives thereof, and to replace these by hydrogen or deuterium atoms. This is effected by electrolyzing the acids or derivatives thereof in a solution containing water or deuterium oxide at a temperature from -10.degree. C. up to the boiling point of the electrolysis liquid.

Electrochemical process for the replacement of halogen atoms in an

Chloroacetic and bromoacetic acids are dehalogenated by electrolysis of aqueous solutions of these acids using carbon cathodes and anodes likewise of carbon or of other conventional electrode materials in undivided or in divided electrolysis cells; the aqueous electrolysis solutions in the undivided cells and in the cathode area of the divided cells contain, in dissolved form, one or more salts of metals having a hydrogen excess-voltage of at least 0.4 V (at a current density of 4,000 A/m.sup.2). Metals having a hydrogen excess-voltage of at least 0.4 V (at a current density of 4,000 A/m.sup.2) are, for example, Cu, Ag, Au, Zn, Cd, Hg, Sn, Pb, Ti, Zr, Bi, V, Ta, Cr and Ni. The process allows high current densities (up to about 8,000 A/m.sup.2) to be used without or virtually without corrosion of the electrodes and without deposit formation on the electrodes.

Growing community of inventors

Kriftel, Germany

Steffen Dapperheld