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
  • C25B3/25—Reduction

Definitions

• Biologically active organic fluorine compounds are often used as crop protection agents or pharmaceuticals. In many cases, such compounds have an increased activity, often coupled with a reduced side effect, effects which can be attributed to the fluorine substitution, such as higher lipid solubility and higher oxidation stability, playing an important role.
• Fluormalonic acid and its derivatives can be prepared by various methods, which, however, mostly produce poor yields and which are also based on very toxic or expensive starting compounds. It is known that diethyl fluoromalonate can be obtained by reacting ethyl monofluoroacetate and ethyl chloroformate under basic conditions (J. Chem. Soc. 1959 , 3286-3289), by halogen exchange from diethyl chloromalonate and potassium fluoride (USSR P 185.878 (1966) - Chem . 67 , 2777 r (1967)) or by fluorination of diethyl malonate with perchloryl fluoride (J. Org. Chem. 31 , 916-918 (1966)).
• R 1 is a halogen with an atomic weight of 35 to 127, that is chlorine, bromine or iodine, preferably chlorine.
• R2 and R3 are identical or different and mean hydroxyl or the group OX, where X is an alkali metal, alkaline earth metal or NH4+ ion, such as lithium, sodium, potassium, magnesium or calcium, or a C1- C12-alkyl, preferably C1-C6-alkyl, or R2 and R3 represent the group NR4R5, wherein R worin and R5 are the same or different and are hydrogen or a hydrocarbon radical having 1 to 12 carbon atoms.
• This hydrocarbon residue can be more aromatic, be cycloaliphatic or aliphatic in nature and advantageously has 1 to 6 carbon atoms.
• it represents phenyl.
• R4 and R5 are preferably hydrogen and / or C1-C6-alkyl.
• Preferred radicals R2 and R3 are hydroxyl radicals and those in which X represents an alkali or NH4+ ion or an alkyl radical.
• Suitable alkyl radicals for X, R4 and R5 are in particular methyl, ethyl, the various propyl, butyl, pentyl and hexyl radicals, but also higher radicals such as the various octyl, decyl and dodecyl radicals.
• Suitable starting compounds for the process according to the invention are therefore chlorofluoronic acid, bromofluoromonic acid and iodofluoronic acid and their esters, amides and salts which satisfy the formula I.
• the process according to the invention can be carried out in divided or undivided electrolysis cells at a temperature from -20 ° C. to the boiling point of the electrolyte at a current density of 1 to 600 mA / cm2 on a cathode made of lead, cadmium, zinc, copper, tin, zircon, Mercury, alloys of at least 2 of these metals or carbon in an electrolyte liquid, the liquid medium of which consists of water and / or an organic solvent.
• the usual diaphragms that are stable in the electrolyte can be made from organic polymers such as polyethylene, polypropylene, polyesters and polysulfones, in particular halogen-containing polymers such as polyvinyl chloride or polyvinylidene fluoride, but preferably from perfluorinated polymers, or diaphragms made from inorganic Use materials such as glass or ceramics, but preferably ion exchange membranes.
• Preferred ion exchange membranes are cation exchange membranes made from polymers such as polystyrene, but preferably from perfluorinated polymers which contain carboxyl and / or sulfonic acid groups.
• polymers such as polystyrene, but preferably from perfluorinated polymers which contain carboxyl and / or sulfonic acid groups.
• the use of stable anion exchange membranes is also possible.
• cathodes are used which are stable in the electrolyte.
• the electrolysis can be carried out either continuously or batchwise and in all customary electrolysis cells, for example in beaker or plate and frame cells or cells with fixed bed or fluidized bed electrodes. Both the monopolar and the bipolar circuit of the electrodes can be used. It is particularly expedient to work in divided electrolysis cells (i.e. with a catholyte and anolyte liquid) with a discontinuous execution of the cathode reaction and continuous operation of the anode reaction.
• the electrode materials used according to the invention have a medium to high hydrogen overvoltage.
• carbon cathodes are preferred, especially for electrolysis in acid electrolytes with a pH of 0 to 4, since some of the electrode materials listed, e.g. Zn, Sn, Cd and Pb, can suffer corrosion.
• all possible carbon electrode materials are possible as carbon cathodes, such as electrode graphites, impregnated graphite materials, carbon felts and also glassy carbon.
• All materials customary in anode reactions can be used as anode material.
• Examples are lead, lead dioxide on lead or other carriers, platinum or with noble metal oxides, for example ruthenium oxide, doped titanium dioxide on titanium or other materials for the development of oxygen from dilute acids such as sulfuric acid, phosphoric acid or tetrafluoroboric acid.
• Carbon or titanium dioxide doped with noble metal oxides on titanium or other materials is also suitable for the development of chlorine from aqueous alkali metal chloride or hydrogen chloride solutions.
• Preferred anolyte liquids are aqueous mineral acids or solutions of their salts, such as dilute sulfuric acid, phosphoric acid, tetrafluoroboric acid, concentrated hydrochloric acid, sodium sulfate or sodium chloride solutions.
• organic solvents e.g. suitable short-chain aliphatic alcohols such as methanol, ethanol, n- and iso-propanol or the various butanols, diols such as ethylene glycol, the various propanediols, but also polyalkylene glycols from ethylene and / or propylene glycol and their ethers, ethers such as tetrahydrofuran, dioxane, amides such as N, N-dimethylformamide, hexamethylphosphoric triamide, N-methyl-2-pyrrolidinone, nitriles such as acetonitrile, propionitrile, ketones such as acetone and other solvents such as sulfolane or dimethyl sulfoxide. Mixtures can also be used. In principle, two-phase electrolysis is also possible with the addition of a water-insoluble organic solvent such as t-butyl methyl ether or methylene chloride in conjunction with a phase transfer catalyst.
• the proportion of organic solvents in the electrolyte in the undivided cell or the catholyte in the divided cell can be 0 to 100% by weight, based on the total amount of the electrolyte or catholyte. It is preferably 10 to 80% by weight.
• soluble salts of metals with a hydrogen overvoltage of at least 0.25 V can be added to the electrolyte in the undivided cell or the catholyte in the divided cell. and / or enthalogenating properties can be added.
• Possible salts are mainly the soluble salts of Cu, Ag, Au, Zn, Cd, Hg, Sn, Pb, Tl, Ti, Zr, Bi, V, Ta, Cr, Ce, Co or Ni, preferably the soluble Pb- , Zn, Cd and Ag salts.
• the preferred anions of these salts are Cl ⁇ , SO4 ⁇ , NO3 ⁇ and CH3COO ⁇ .
• the salts can be added to the electrolysis solution or can also be generated in the solution, for example by adding oxides, carbonates etc. - in some cases also the metals themselves (if soluble).
• Their concentration in the electrolyte of the undivided cell and in the catholyte of the divided cell is expediently about 10 auf to 10% by weight, preferably about 10 ⁇ 3 to 5% by weight, in each case based on the total amount of the electrolyte or catholyte, set.
• Electrolysis can be carried out in a wide pH range, most preferably at a pH from 0 to 13, preferably from 0.5 to 12.
• acids such as hydrochloric, boric, phosphoric, sulfur or tetrafluoroboric acid and / or formic, acetic or citric acid and / or their salts
• acids such as hydrochloric, boric, phosphoric, sulfur or tetrafluoroboric acid and / or formic, acetic or citric acid and / or their salts
• work is of course only carried out in those pH ranges in which no insoluble compounds form.
• organic bases may also be necessary to set the pH value which is favorable for the electrolysis and / or have a favorable influence on the course of the electrolysis.
• Suitable are primary, secondary and tertiary C2-C12 alkyl and cycloalkylamines, aromatic and aliphatic-aromatic (in particular araliphatic) amines and their salts, inorganic bases such as alkali and alkaline earth metal hydroxides such as, for example, Li, Na, K, Cs, Mg, Ca, Ba hydroxide, quaternary ammonium salts, with anions, such as, for example, the fluorides , Chlorides, bromides, iodides, acetates, sulfates, hydrogen sulfates, tetrafluoroborates, phosphates and hydroxides, whereby, of course, combinations of cations and anions are not taken into account which lead to insoluble products under the conditions used.
• ammonium salts are, for example, those of C1-C12-tetraalkylammonium, C1-C12-trialkylarylammonium and C1-C12-trialkylmonoalkylarylammonium.
• anionic or cationic emulsifiers can also be used in amounts of 0.01 to 15, preferably 0.03 to 10 percent by weight, based on the total amount of the electrolyte or catholyte.
• compounds can be added to the electrolyte which are oxidized at a more negative potential than the released halogen ions in order to avoid the formation of the free halogen.
• the salts of oxalic acid, methoxyacetic acid, glyoxylic acid, formic acid and / or hydrochloric acid are suitable, for example.
• Electrolysis is preferably carried out at a current density of 10 to 500 mA / cm2.
• the electrolysis temperature is expediently in the range from -10 ° C. to the boiling point of the electrolysis liquid, preferably from 5 to 90 ° C., in particular from 15 to 80 ° C.
• the electrolysis product is worked up in a customary manner, for example by extraction from the reaction medium or by distilling off the solvent.
• the compounds added to the catholyte can thus be returned to the process.
• the electrolysis is carried out in the corresponding alcohol. After the electrolysis has ended, the majority of the alcohol is distilled off and the acid is esterified by customary methods.
• Jacketed glass pot cell with a volume of 350 ml; Anode: platinum mesh (20 cm2); Cathode area: 12 cm2; Electrode distance: 1.5 cm; Anolyte: dilute aqueous sulfuric acid; Cation exchange membrane; Two-layer membrane made from a copolymer of perfluorosulfonylethoxy vinyl ether and tetrafluoroethylene (®Nafion 324 from E.I. du Pont de Nemours & Co., Wilmington, USA); Mass transfer by magnetic stirrer.

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• Chemical & Material Sciences (AREA)
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• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 1988
  • 1988-01-30 DE DE3802745A patent/DE3802745A1/de not_active Withdrawn
• 1989
  • 1989-01-18 EP EP89100767A patent/EP0326855B1/fr not_active Expired - Lifetime
  • 1989-01-18 DE DE8989100767T patent/DE58900078D1/de not_active Expired - Fee Related
  • 1989-01-26 US US07/302,440 patent/US4950367A/en not_active Expired - Fee Related
  • 1989-01-27 JP JP1016496A patent/JPH01222079A/ja active Pending

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