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US3909376A - Electrolytic manufacture of alkyl-substituted hydroquinones - Google Patents

Electrolytic manufacture of alkyl-substituted hydroquinones Download PDF

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US3909376A
US3909376A US529284A US52928474A US3909376A US 3909376 A US3909376 A US 3909376A US 529284 A US529284 A US 529284A US 52928474 A US52928474 A US 52928474A US 3909376 A US3909376 A US 3909376A
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acetone
alkylphenol
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Dieter Degner
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    • 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

Definitions

  • the invention relates to a process for the manufacture of alkylhydroquinones by electrolytic oxidation of alkylphenols and subsequent electrolytic reduction of the quinones thus obtained.
  • German Published application No. 1,643,558 has disclosed converting unsubstituted phenol into hydroquinone in 90 per cent yield through appropriate choice of the electrolysis parameters such as current density, depolarizer and electrolyte concentration.
  • the current efficiencies are above 60%. If attempts are made to apply these conditions to the anodic oxidation of alkylsubstituted phenols, the corresponding hydroquinones are obtained, but the yields are very low and the current efficiencies even drop below
  • Chemical Communications 1971, pp. 1,643, et seq. discloses that dimethylphenol can be oxidized electrolytically to dimethylquinone in the presence of acetonitrile as the solvent.
  • alkylhydroquinones of the general formula in which R is alkyl of l to 4 carbon atoms and n is an integer from 1 to 3 can be manufactured particularly advantageously in an electrolyticprocess wherein alkylphenols of the formula group, are oxidized anodically in a non-oxidizing aqueous mineral acid in the presence of a watersoluble ketone and the reaction mixture containing the corresponding alkylquinones is reduced cathodically.
  • R is methyl.
  • the para-position, where oxidation is to take place, in the initial phenol II must of course always be unsubstituted.
  • suitable phenols are 2- methylphenol, 2,6-dimethylphenol, 2,3,6- trimethylphenol and 2,3,5-trimethylphenol.
  • the electrolysis is carried out in the presence of an aqueous solution of a non-oxidizing mineral acid, especially sulfuric acid.
  • a non-oxidizing mineral acid especially sulfuric acid.
  • concentration of the mineral acid used is from 1 to 20 percent by weight, especially from 5 to 10 percent by weight.
  • the temperature is maintained at its ambient value or slightly above, for example at from 20 to 40C. Under no circumstances should the boiling points of the solvents used be exceeded.
  • the anodes used are lead dioxide, or electrodes coated with lead dioxide, or electrodes of noble metals, such as, for example, platinum, platinized titanium or gold. Lead dioxide anodes are preferred.
  • Cathodes which can be used are lead, mercury, cadmium, tin, zinc, copper, nickel, silver amalgam and lead amalgam electrodes. Lead electrodes have acquired particular importance.
  • the anodic oxidation of the phenols is preferably carried out in a compartmented anode chamber and the alkylquinones obtained are then reduced in a subsequent stage, in a cathode chamber which is also compartmented. It has proved particularly convenient to use a compartmented cell, carry out the oxidation of the alkylphenols II in the anode chamber, pass the solution thus obtained into the cathode chamber and there carry out the electrochemical reduction to the corresponding hydroquinone.
  • An essential feature of the invention is the use of a water-soluble ketone as the solvent.
  • suitable water-soluble ketones are acetone, methyl ethyl ketone and diethyl ketone.
  • Acetone has proved a particularly suitable solvent.
  • the electrolysis mixture used advantageously contains from 20 to percent by weight, especially from 40 to 60 percent by weight, of acetone.
  • the initial electrolysis mixture preferably contains from 1 to 10 percent by weight of alkylphenols of the formula II.
  • alkylhydroquinones obtained as end products are generally isolated by evaporating off the solvent. They can also be extracted with a suitable waterimmiscible solvent and be isolated therefrom by conventional methods, for example precipitation or fractional crystallization.
  • Alkyl-substituted hydroquinones manufactured by the process of the invention can be used for the manufacture of plant protection agents, dyes or biologically active materials, for example vitamin E (cf. S.F. Dyke; On completion of the electrolysis, the catholyte is The Chemistry of the Vitamins, pp. 256 et seq., Interworked up analogously to Example 2. This gives trimescience Publishers 1965). thylhydroquinone which is over 90 percent pure.
  • the Alkylhydroquinones can also be used as polymeriy l (based ri y p Converted) is zation inhibitors (cf. Belgian Pat. No. 779,388). 774%- The Examples which follow illustrate the process of COMPARATIVE EXAMPLE the invention.
  • the yield of 2,6-dimethyl-o-benzoquinone (based in which R is alkyl of l to 4 carbon atoms and n is an on 2,6-dimethylphenol converted) is 86.2% and the n g from 1 t0 wherein an lkylph n f h g ncurrent efficiency is 54.8%.
  • eral formula EXAMPLE 2 Electrochemical synthesis of 2.6-dimethylhydroquinone 0H Apparatus Anode Anolyte As in Example I II Cathode n l and Q Catholyte; the unolyte from Example 1.
  • y -P' trolysis mixture contains from 20 to percent by benzoquinone is obtained in 84.6 percent yield (based i h f acetone 2,3,64rimethylphen0l Converted) The current 7.
  • 60 trolysis mixture contains from 1 to 10 percent by weight of alkylphenol.

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

Abstract

Alkylhydroquinones with from 1 to 3 alkyl radicals, which can contain from 1 to 4 carbon atoms, are produced by electrolytic oxidation of the corresponding alkylphenols which are unsubstituted in the para-position to the hydroxyl group, followed by electrolytic reduction of the resulting alkylquinones, wherein the electrolysis is carried out in the presence of a non-oxidizing aqueous mineral acid and in the presence of a water-soluble ketone.

Description

United States Patent Degner [4 1 Sept. 30, 1975 ELECTROLYTIC MANUFACTURE OF ALKYL-SUBSTITUTED HYDROQUINONES Inventor: Dieter Degner, Ludwigshafen,
Germany BASF Aktiengesellschaft, Ludwigshafen, Rhine, Germany Filed: Dec. 4, 1974 Appl. N0.: 529,284
Assignee:
Foreign Application Priority Data Dec. 5, 1973 Germany 2360494 US. Cl 204/73; 204/78 C25B 3/02; C25B 3/04 Field of Search 204/72, 73, 78
References Cited UNITED STATES PATENTS 10/1971 Covitz et a] 204/78 3,721,615 3/1973 Fremery et a1 204/73 R Primary Examiner-R. L. Andrews Attorney, Agent, or FirmJohnston, Keil, Thompson & Shurtleff [5 7 ABSTRACT 9 Claims, No Drawings ELECTROLYTIC MANUFACTURE OF ALKYL-SUBSTITUTED HYDROQUINONES This application discloses and claims subject matter described in German Pat. application No. P 23 60 494.6, filed Dec. 5, 1973, which is incorporated herein by reference.
The invention relates to a process for the manufacture of alkylhydroquinones by electrolytic oxidation of alkylphenols and subsequent electrolytic reduction of the quinones thus obtained.
The anodic oxidation of phenols to the corresponding benzoquinones in a compartmented cell; and the electrochemical synthesis of hydroquinones in a noncompartmented cell, have been known for a considerable time (cf. Berichte der deutschen Chemischen Gesellschaft, Vol. 47, p. 2,003 (1914), Helv. Chim. Acta, Vol. 2, p. 583 (1919), Vol. 8, p. 74(1925), Vol.10, p. 40 1927) and Vol. 10, p. 102 (1927). However, in this process neither the product yield nor the current efficiency are very high, and furthermore a number of un desired byproducts are formed. These by-products necessitate expensive purification operations.
German Published application No. 1,643,558 has disclosed converting unsubstituted phenol into hydroquinone in 90 per cent yield through appropriate choice of the electrolysis parameterssuch as current density, depolarizer and electrolyte concentration. The current efficiencies are above 60%. If attempts are made to apply these conditions to the anodic oxidation of alkylsubstituted phenols, the corresponding hydroquinones are obtained, but the yields are very low and the current efficiencies even drop below Further, Chemical Communications 1971, pp. 1,643, et seq. discloses that dimethylphenol can be oxidized electrolytically to dimethylquinone in the presence of acetonitrile as the solvent. However, if attempts are made to reduce an alkylquinone, thus obtained, to the corresponding hydroquinone, the yields obtained leave much to be desired. An essential disadvantage is that the hydroquinones obtained are insufficiently pure for further conversion and thus necessitate an expensive purification process. I
I have found that alkylhydroquinones of the general formula in which R is alkyl of l to 4 carbon atoms and n is an integer from 1 to 3 can be manufactured particularly advantageously in an electrolyticprocess wherein alkylphenols of the formula group, are oxidized anodically in a non-oxidizing aqueous mineral acid in the presence of a watersoluble ketone and the reaction mixture containing the corresponding alkylquinones is reduced cathodically.
It is an advantage of the new process that both the yields and the current efficiences are good. A decisive advantage of the new process is that the hydroquinones as obtained are more than 90 per cent pure and require no additional purification before further processing.
In the preferred alkylphenols of the formula II, R is methyl. The para-position, where oxidation is to take place, in the initial phenol II must of course always be unsubstituted. Examples of suitable phenols are 2- methylphenol, 2,6-dimethylphenol, 2,3,6- trimethylphenol and 2,3,5-trimethylphenol.
2,6-Dimethylphenol and 2,3,6-trimethylphenol have acquired particularly great importance in industry.
The electrolysis is carried out in the presence of an aqueous solution of a non-oxidizing mineral acid, especially sulfuric acid. In general, the concentration of the mineral acid used is from 1 to 20 percent by weight, especially from 5 to 10 percent by weight.
During the anodic oxidation and the cathodic reduction, the temperature is maintained at its ambient value or slightly above, for example at from 20 to 40C. Under no circumstances should the boiling points of the solvents used be exceeded.
It is advantageous to maintain current densities greater than 5 amperes per dm during the electrolysis. In general, the range of current densities used is from 5 to 20 amperes per dm The anodes used are lead dioxide, or electrodes coated with lead dioxide, or electrodes of noble metals, such as, for example, platinum, platinized titanium or gold. Lead dioxide anodes are preferred.
Cathodes which can be used are lead, mercury, cadmium, tin, zinc, copper, nickel, silver amalgam and lead amalgam electrodes. Lead electrodes have acquired particular importance.
The anodic oxidation of the phenols is preferably carried out in a compartmented anode chamber and the alkylquinones obtained are then reduced in a subsequent stage, in a cathode chamber which is also compartmented. It has proved particularly convenient to use a compartmented cell, carry out the oxidation of the alkylphenols II in the anode chamber, pass the solution thus obtained into the cathode chamber and there carry out the electrochemical reduction to the corresponding hydroquinone.
An essential feature of the invention is the use of a water-soluble ketone as the solvent. Examples of suitable water-soluble ketones are acetone, methyl ethyl ketone and diethyl ketone. Acetone has proved a particularly suitable solvent. The electrolysis mixture used advantageously contains from 20 to percent by weight, especially from 40 to 60 percent by weight, of acetone.
The initial electrolysis mixture preferably contains from 1 to 10 percent by weight of alkylphenols of the formula II.
The alkylhydroquinones obtained as end products are generally isolated by evaporating off the solvent. They can also be extracted with a suitable waterimmiscible solvent and be isolated therefrom by conventional methods, for example precipitation or fractional crystallization.
Alkyl-substituted hydroquinones manufactured by the process of the invention can be used for the manufacture of plant protection agents, dyes or biologically active materials, for example vitamin E (cf. S.F. Dyke; On completion of the electrolysis, the catholyte is The Chemistry of the Vitamins, pp. 256 et seq., Interworked up analogously to Example 2. This gives trimescience Publishers 1965). thylhydroquinone which is over 90 percent pure. The Alkylhydroquinones can also be used as polymeriy l (based ri y p Converted) is zation inhibitors (cf. Belgian Pat. No. 779,388). 774%- The Examples which follow illustrate the process of COMPARATIVE EXAMPLE the invention.
If the procedure described in Examples 3 and 4 is fol- EXAMPLE 1 lowed but acetonitrile is used instead of acetone, the I 10 yield of 2,3,6-trimethylhydroquinone is 45 55% and Anodic oxidation of 2,6dimethylphenol. the. purity is only 70 75%. Apparatus: compartmented cell with Cation exchange membrane w l Anode: PbO electrode; surface area: 0.66 dm e C Anolyte: 24.4 g (0.2 mole) of 2,6-dimethylphenol 1. A process for the electrochemical manufacture of 550 ml of H20 450 ml of acetone an alkylhydroquinone of the general formula I 49 g of concentrated H2804 Catholyte: IN H2504 Cathode: Pb electrode Charge O: 0.8 F Y Current l: l0 A OH 1 On completion of the electrolysis, a sample of the an- (R olyte was taken, the. acetone was distilled off and the residue was repeatedly extracted with ether. After dis- I OH tilling off the ether, the 2,6-dimethyl-p-benzoquinone and unconverted starting material are determined by gas chromatography. According to these determinations, the yield of 2,6-dimethyl-o-benzoquinone (based in which R is alkyl of l to 4 carbon atoms and n is an on 2,6-dimethylphenol converted) is 86.2% and the n g from 1 t0 wherein an lkylph n f h g ncurrent efficiency is 54.8%. eral formula EXAMPLE 2 Electrochemical synthesis of 2.6-dimethylhydroquinone 0H Apparatus Anode Anolyte As in Example I II Cathode n l and Q Catholyte; the unolyte from Example 1.
Af o lt' fth ltrlsis,theat c mp e [on o e ec O y Ce one Is in which R and n have the above meanings, and which distilled off and the residue is steam-distilled to remove 1S unsubstituted in the para-position to the hydroxyl unconverted 2,6-dimethylphenol. On cooling the resi- 40 g p is Oxidized anodicany in a nomoxidizing q duefiom h Steam dlsnn'fmoni z'dlmethylhydroqul' ous mineral acid and in the presence of a water-soluble f preclpltates' The yled based on ketone, and the reaction mixture containing the corredimethylphenol converted. The 2,6-dimethylhydroquisponding alkylquinone is reduced cathodicany obtamed 90% pure 2. a process as claimed in claim 1, wherein the anodic EXAMPLE 3 5 oxidation and the cathodic reduction are carried out at room temperature or at a temperature of up to 40C. 3. A process as claimed in claim 1, wherein sulfuric Anodic oxidation of 2,3,6-trimethylphenol Apparatus: compartmented cellowgthzatzion exchange membrane acid of from 1 to 20 percent strength by weight iS used 1123 i i iii i rfw i ei er 2,3,6- trimethyIphenQI as the non'oxldlzmg aque9us mfneral 500 ml of H20 4. A process as claimed in claim 1, wherein a current :3 0f d H 0 density of 5 to 20 amperes per dm is maintained during catholyte: i z gj C Is the electrolysis. I I Cathode: Pb 5. A process as claimed in claim 1, wherein acetone, QI R115 methyl ethyl ketone or diethyl ketone is used as the water-soluble ketone; on Working p a sample of the material leaving the 6. A process as claimed in claim 1, wherein the elecelectrolysis, analogously to Example 1, y -P' trolysis mixture contains from 20 to percent by benzoquinone is obtained in 84.6 percent yield (based i h f acetone 2,3,64rimethylphen0l Converted) The current 7. A process as claimed in claim 1, wherein the elecciency is 54%. 60 trolysis mixture contains from 1 to 10 percent by weight of alkylphenol.
8. A process as claimed in claim 1, wherein an alkylphenol of the formula II, in which R is methyl, is used.
9. A process as claimed in claim 1, wherein 2- EXAMPLE 4 Electrochemical synthesis of trimethylhydroquinone Apparatus v Anode methylphenol, 2,6-dimethylphenol, 2,3,6- Amlyte As Example 3 trimethylphenol or 2,3,5-trimethylphenol is used as the Cathode I and Q alkylphenol.
Catholyte: the anolyte from Example 3. =i

Claims (9)

1. A PROCESS FOR THE ELCTROCHEMICAL MANUFACTURE OF AN ALKYLHYDROQUINONE OF THE GENERAL FORMULA
2. a process as claimed in claim 1, wherein the anodic oxidation and the cathodic reduction are carried out at room temperature or at a temperature of up to 40*C.
3. A process as claimed in claim 1, wherein sulfuric acid of from 1 to 20 percent strength by weight is used as the non-oxidizing aqueous mineral acid.
4. A process as claimed in claim 1, wherein a current density of 5 to 20 amperes per dm2 is maintained during the electrolysis.
5. A process as claimed in claim 1, wherein acetone, methyl ethyl ketone or diethyl ketone is used as the water-soluble ketone.
6. A process as claimed in claim 1, wherein the electrolysis mixture contains from 20 to 60 percent by weight of acetone.
7. A process as claimed in claim 1, wherein the electrolysis mixture contains from 1 to 10 percent by weight of alkylphenol.
8. A process as claimed in claim 1, wherein an alkylphenol of the formula II, in which R is methyl, is used.
9. A process as claimed in claim 1, wherein 2-methylphenol, 2,6-dimethylphenol, 2,3,6-trimethylphenol or 2,3,5-trimethylphenol is used as the alkylphenol.
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4464236A (en) * 1982-05-10 1984-08-07 The Dow Chemical Company Selective electrochemical oxidation of organic compounds
US5098531A (en) * 1988-03-24 1992-03-24 Istituto Guido Donegani S.P.A. Electrochemical synthesis of 2-aryl-hydroquinones
US20070072943A1 (en) * 2005-09-15 2007-03-29 Miller Guy M Tail variants of redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
EP2471530A1 (en) 2005-06-01 2012-07-04 Edison Pharmaceuticals, Inc. Redox-active Therapeutics For Treatment Of Mitochondrial Diseases And Other Conditions And Modulation Of Energy Biomarkers
US9278085B2 (en) 2006-02-22 2016-03-08 Edison Pharmaceuticals, Inc. Side-chain variants of redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US20160175875A1 (en) * 2013-08-07 2016-06-23 Meler Aplicadores De Hot-Melt, S.A. Melter
US9399612B2 (en) 2008-09-10 2016-07-26 Edison Pharmaceuticals, Inc. Treatment of pervasive developmental disorders with redox-active therapeutics
US10703701B2 (en) 2015-12-17 2020-07-07 Ptc Therapeutics, Inc. Fluoroalkyl, fluoroalkoxy, phenoxy, heteroaryloxy, alkoxy, and amine 1,4-benzoquinone derivatives for treatment of oxidative stress disorders

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3616324A (en) * 1970-02-19 1971-10-26 Union Carbide Corp Electrochemical conversion of phenol to hydroquinone
US3721615A (en) * 1971-02-24 1973-03-20 Union Rheinische Braunkohlen Process for the production of hydroquinone

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3616324A (en) * 1970-02-19 1971-10-26 Union Carbide Corp Electrochemical conversion of phenol to hydroquinone
US3721615A (en) * 1971-02-24 1973-03-20 Union Rheinische Braunkohlen Process for the production of hydroquinone

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4464236A (en) * 1982-05-10 1984-08-07 The Dow Chemical Company Selective electrochemical oxidation of organic compounds
US5098531A (en) * 1988-03-24 1992-03-24 Istituto Guido Donegani S.P.A. Electrochemical synthesis of 2-aryl-hydroquinones
US11021424B2 (en) 2005-06-01 2021-06-01 Ptc Therapeutics, Inc. Redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US9447006B2 (en) 2005-06-01 2016-09-20 Edison Pharmaceuticals, Inc. Redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
EP2471530A1 (en) 2005-06-01 2012-07-04 Edison Pharmaceuticals, Inc. Redox-active Therapeutics For Treatment Of Mitochondrial Diseases And Other Conditions And Modulation Of Energy Biomarkers
EP2564843A1 (en) 2005-06-01 2013-03-06 Edison Pharmaceuticals, Inc. Redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
EP2564842A1 (en) 2005-06-01 2013-03-06 Edison Pharmaceuticals, Inc. Redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US7432305B2 (en) 2005-09-15 2008-10-07 Edison Pharmaceuticals, Inc. Tail variants of redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US20070072943A1 (en) * 2005-09-15 2007-03-29 Miller Guy M Tail variants of redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US9278085B2 (en) 2006-02-22 2016-03-08 Edison Pharmaceuticals, Inc. Side-chain variants of redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US9932286B2 (en) 2006-02-22 2018-04-03 Bioelectron Technology Corporation Side-chain variants of redox-active therapeutics for treatment of mitochondrial diseases and other conditions and modulation of energy biomarkers
US9399612B2 (en) 2008-09-10 2016-07-26 Edison Pharmaceuticals, Inc. Treatment of pervasive developmental disorders with redox-active therapeutics
US10736857B2 (en) 2008-09-10 2020-08-11 Ptc Therapeutics, Inc. Treatment of pervasive developmental disorders with redox-active therapeutics
US10105325B2 (en) 2008-09-10 2018-10-23 Bioelectron Technology Corporation Treatment of pervasive developmental disorders with redox-active therapeutics
US20160175875A1 (en) * 2013-08-07 2016-06-23 Meler Aplicadores De Hot-Melt, S.A. Melter
US10010903B2 (en) * 2013-08-07 2018-07-03 Meler Aplicadores De Hot-Melt, S.A. Melter
US10703701B2 (en) 2015-12-17 2020-07-07 Ptc Therapeutics, Inc. Fluoroalkyl, fluoroalkoxy, phenoxy, heteroaryloxy, alkoxy, and amine 1,4-benzoquinone derivatives for treatment of oxidative stress disorders
US10981855B2 (en) 2015-12-17 2021-04-20 Ptc Therapeutics, Inc. Fluoroalkyl, fluoroalkoxy, phenoxy, heteroaryloxy, alkoxy, and amine 1,4-benzoquinone derivatives for treatment of oxidative stress disorders
US11680034B2 (en) 2015-12-17 2023-06-20 Ptc Therapeutics, Inc. Fluoroalkyl, fluoroalkoxy, phenoxy, heteroaryloxy, alkoxy, and amine 1,4-benzoquinone derivatives for treatment of oxidative stress disorders

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