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

Definitions

• This invention relates to a new process for the preparation of alkyl substituted benzaldehyde dialkyl acetals by electrooxidation of alkyl toluenes.
• EP-PS 12 240 describes a process for the preparation of benzaldehyde dialkyl acetals, in which the electrooxidation of the toluenes is carried out in alcoholic solution and in the presence of tetraalkylammonium sulfonates and phosphates as conductive salts.
• collidine for example, is added as an auxiliary base to the electrolyte.
• electro-oxidation of p-xylene and 4-tert-butyl toluene yields of only 64 and '55% are erreitht by this method.
• FR-PS 2 351 932 describes a process in which toluenes are anodically oxidized on Pt electrodes.
• electrolytes consist of toluene, an inert organic solvent such as methylene chloride, methanol and an acid containing H 3 S groups consist.
• the electrooxidation of p-xylene gives this method drive a mixture that contains 4-methylbenzaldehyde but no 4-methylbenzaldehyde dimethyl acetal in addition to ether and ester compounds.
• the benzaldehyde dialkyl acetals are obtained by avoiding the disadvantages described in a particularly economical manner and in good yields by the process according to the invention.
• Alkyl radicals with I to 8 carbon atoms are, for example, methyl, ethyl, isopropyl, n-, iso- and tert-butyl groups.
• Preferred alkyltoluenes are xylenes and butyltoluenes, such as p-xylene and 4-tert-butyltoluene. Of the two alkanols, methanol is of particular technical interest.
• Suitable acids containing H 3 S groups are, for example, acids of the formula R 3 SO 3 H , in which R 3 represents an alkyl, aryl, hydroxyl or alkoxy group.
• Preferred acids are methanesulfonic acid, benzenesulfonic acid and methylsulfuric acid, especially sulfuric acid.
• the method according to the invention does not require a special electrolysis cell; it is preferably carried out in undivided electrolysis cells.
• Preferred electrolytes are those which have an alkanol content of 70 to 90% by weight, alkyltoluene of 8.5 to 30% by weight and acids of 0.05 to 1.5% by weight.
• All anode materials which are customary per se and are stable under the electrolysis conditions can be used as anodes, graphite anodes are preferably used.
• steel, nickel, precious metals or graphite can be used as cathode materials.
• the current densities are, for example, 2 to 20 A / dm 2
• electrolysis is preferably carried out at current densities of 2 to 12 A / dm 2 .
• the electrolysis temperature is limited by the boiling point of the alkanol. When using methanol, electrolysis is carried out, for example, at temperatures up to 60 ° C., preferably at 20 to 60 ° C.
• the process according to the invention offers the possibility of largely converting the alkyltoluenes and the alkylbenzylalkyl ethers which have passed through as intermediates without the selectivities of the electrooxidation being significantly impaired.
• the electrolysis is carried out with 2.8 to 7, preferably 4 to 6.5 F per mole of alkyl toluene.
• the process can be carried out batchwise or continuously.
• the electrolysis discharges can be worked up in a very simple manner. One proceeds e.g. so that the small amount of acid is neutralized with an equivalent amount of an alkali. So you give e.g. when using sulfuric acids sodium hydroxide or sodium methylate.
• the alkanol and any alkyltoluenes and alkylbenzylalkyl ethers which may still be present are then distilled off and, if appropriate, returned to the electrolysis.
• the alkylbenzaldehyde dialkyl acetals can then be further purified by vacuum distillation.
• the benzaldehyde dialkyl acetals obtainable by the new process are valuable precursors for fragrances and fungicides.
• the electrolyte is pumped through a heat exchanger at 200 l / h during the electrolysis.
• Example 2 It is electrolyzed and worked up as indicated in Example 1. This gives 51.6 g of p-xylene, 34.4 g of 4-methylbenzyl ether and 366.9 g of 4-methylbenzaldehyde dimethyl acetal. This corresponds to a yield of 67.6%.
• the electrolyte is pumped through a heat exchanger at 200 l / h during the electrolysis.
• Example 4 It is electrolyzed and worked up as described in Example 4. There are 11.8 g of 4-tert-butylbenzyl methyl ether and 353.6 g of 4-tert-butylbenzaldehyde dimethyl acetal. This corresponds to a yield of 74.3%.

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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)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (2)

Publications (3)

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ID=6202042

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Cited By (6)

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• 1983
  • 1983-06-22 DE DE19833322399 patent/DE3322399A1/de not_active Withdrawn
• 1984
  • 1984-06-15 EP EP84106858A patent/EP0129795B1/fr not_active Expired
  • 1984-06-15 DE DE8484106858T patent/DE3469444D1/de not_active Expired
  • 1984-06-20 JP JP59125433A patent/JPH0641638B2/ja not_active Expired - Lifetime
  • 1984-06-21 US US06/623,210 patent/US4539081A/en not_active Expired - Lifetime

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