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
  • C25B3/23—Oxidation
• • 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
  • C25B3/01—Products
  • C25B3/07—Oxygen containing compounds

Definitions

• This invention relates to a new process for the preparation of benzaldehyde dialkyl acetals by electrooxidation of benzyl alkyl ethers.
• the electrochemical oxidation of toluene derivatives in the presence of an alkanol to the corresponding benzaldehyde dialkyl acetals is e.g. from J. Chem. Soc. Perkin 1 (1978) 708 to 715, DE-PS 28 48 397 or EP-PS 12 240 known.
• the benzaldehyde dialkyl acetals are only obtained with good selectivity if the toluene derivative used has a substituent with electron donor properties in the 4-position.
• the unsubstituted toluene can only be converted into the dialkylacetals of benzaldehyde in very poor selectivities under the conditions of electrooxidation (see FR-PS 2 351 932).
• the process according to the invention can be carried out in electrolysis cells which are conventional per se.
• An undivided flow cell with a bipolar electrode arrangement is particularly suitable.
• Precious metals such as Pt or metal oxides such as Pb0 2 or Ru0 2 are suitable as anode materials.
• the preferred anode material is graphite.
• the electrolyte consists of the benzyl alkyl ether, the alcohol and a basic electrolyte.
• Bases, neutral salts and acids can be used as the basic electrolyte.
• Bases are, for example, alkali hydroxides, such as NaOH or KOH, and alkali alcoholates, such as NaOCH 3 .
• Fluorides such as KF, sulfonates such as KS0 3 C 6 H 5 or alkyl sulfates such as (CH 3 ) 4 N + SO 4 CH - are used as neutral salts.
• acids used are sulfuric acids or sulfonic acids, such as CH 3S 0 3H or C 6 H 5 SO 3 H.
• acidic or neutral electrolytes are preferably used.
• the electrolyte composition can be varied within wide limits.
• An electrolyte is preferably used which has a content of 10 to 50% by weight of the benzyl alkyl ether and 50 to 90% by weight of the alcohol, the electrolyte additionally also 0.1 to 5% by weight, based on the mixture from benzyl alkyl ether and alcohol, an acid or a neutral salt.
• Electrolysis is carried out at current densities of, for example, 0.5 to 20 A / dm 2 , preferably 2 to 10 A / dm 2.
• the temperatures during the electrolysis can likewise be chosen within wide limits.
• Electrolysis is preferably carried out at temperatures up to 5 ° C. below the boiling point of the alkanol.
• a great advantage of the process is that more than 50% of the benzylalkyl ethers can be converted without reducing the selectivity of the electrooxidation.
• the alkanols which also serve as solvents, can be returned to the electrolysis without any intermediate cleaning, without the electrolysis being adversely affected by the formation of deposits on the electrodes, as is frequently observed in industrial organic electrolysis.
• the method can thus also be carried out continuously in a simple manner.
• the benzaldehyde alkyl acetals obtained by the process are valuable fragrances.
• the electrolyte is pumped through the cell at 200 l / h during the electrolysis.
• the electrolyte is pumped through the cell at 200 l / h during the electrolysis.
• Electrosynthesis of benzaldehyde dimethyl acetal (basic electrolyte) The electrolyte is pumped through the cell at 200 l / h during the electrolysis.
• the electrolyte is pumped through the cell at 200 l / h during the electrolysis.
• the electrolysis discharge is first neutralized with NaOH. Then ethanol is distilled off at normal pressure and 75 to 90 ° C. The precipitated salt is separated off on a suction filter and the filtrate is fractionated at 80 to 100 ° C. and 10 to 20 torr. This gives 123.6 g of benzyl ethyl ether and 262.5 g of benzaldehyde diethylacetal. This results in a conversion of benzyl ethyl ether of 64.2 Z, a yield of benzaldehyde diethylacetal of 57.5% and a selectivity for benzaldehyde diethylacetal of 89.6%.

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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)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6226702

Family Applications (1)

Country Status (2)

Cited By (3)

Family Cites Families (1)

• 1984
  • 1984-02-03 DE DE19843403789 patent/DE3403789A1/de not_active Withdrawn
• 1985
  • 1985-01-25 DE DE8585100746T patent/DE3560200D1/de not_active Expired
  • 1985-01-25 EP EP85100746A patent/EP0152801B1/fr not_active Expired

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