Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C68/00—Preparation of esters of carbonic or haloformic acids
  • C07C68/06—Preparation of esters of carbonic or haloformic acids from organic carbonates

Definitions

• the invention relates to a process for the preparation of aromatic carbonic acid esters from aliphatic carbonic acid esters and phenols by transesterification in the presence of organotin compounds.
• transesterification of aliphatic carbonic acid esters with phenols in the presence of strong bases or of alkali compounds is known according to DBP 971 790, 1 020 184, 1 026 958 and 1 031 512.
• Transesterification processes catalyzed in this way have the disadvantage that they are not very selective, so that considerable amounts of carbon dioxide are released in a side reaction.
• DOS 2 528 412 and 2 552 907 describe transesterification processes for the production of aromatic carbonic acid esters, in which Lewis acids, ie transition metal halides or the corresponding acyloxy, alkoxy or aryloxy compounds, are used as catalysts.
• Lewis acids ie transition metal halides or the corresponding acyloxy, alkoxy or aryloxy compounds
• catalysts on Titan asis have the disadvantage that they color the end products strongly red-brown. This coloring is particularly unpleasant if the end products do not have to be purified by recrystallization or distillation, as is the case with polycarbonates, for example.
• the object of the invention was achieved by using organotin compounds as transesterification catalysts.
• the invention therefore relates to processes for the preparation of aromatic carbonic acid esters by transesterification of dialkyl carbonates with phenols with the elimination of alcohols in the presence of catalysts, which are characterized in that organotin compounds are used as catalysts.
• the favorable catalytic action of the catalysts according to the invention is surprising since they cannot be called Lewis acids.
• the organotin halogen compounds such as dibutyltin dichloride or dioctyltin dichloride, in which a formal relationship to typical Lewis acids such as aluminum trichloride or titanium tetrachloride could most likely be assigned, are completely ineffective.
• the organotin compounds used according to the invention may therefore not contain any direct tin-halogen compound.
• organotin compounds for example include trimethyltin, Triäthylzinnbenzoat, tributyltin acetate, triphenyltin acetate, dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, Dibutylzinnadipinat, Methoxytributylzinn, Methoxytriphenylzinn, Phenoxytriäthylzinn, dimethoxydibutyltin, Dimethylzinnglykolat, Diäthoxydibutylzinn, Diphenoxydibutylzinn, Dimethoxydiphenylzinn, Triäthylzinnhydroxid, triphenyltin hydroxide, Hexaäthylstannoxan , Hexabutylstannoxane, tetrabutyldiphenoxystannoxane, dibutyltin oxide and diocty
• those compounds are used whose vapor pressure is low even at the required reaction temperatures, i.e. those with organometallically bonded alkyl radicals of at least four carbon atoms.
• Preferred dialkyl carbonates are those of the general formula (III) used, in which R 7 is an alkyl radical having C 1 -C 10 .
• Dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, dioctyl carbonate, diisooctyl carbonate and dicyclohexyl carbonate can preferably be used.
• Suitable phenols are preferably those of the general formula (IV) in which X is hydrogen, an alkyl radical with C1-C3, a halogen atom, preferably chlorine, or a nitro group and n is 1 or 2.
• Particularly preferred phenols for the process according to the invention are phenol, o, m, p-cresol, o, m, p-chlorophenol, o, m, p-ethylphenol, o, m, p-propylphenol, o, m, p -Nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol and 3,4-dimethylphenol are used.
• bisphenols such as dihydroxydiarylalkanes with C 1 -C 4 in the alkyl radical, for example bisphenol A, can also be used. They are not split under the process conditions and can thus be converted directly into polycarbonates. Based on pure raw materials, these are almost colorless and do not require any additional cleaning steps.
• the catalysts are used in concentrations of about 0.001-20% by weight, based on the total amount of the reaction mixture.
• the weight ratio of dialkyl carbonate: phenol can vary within wide limits and is between about 1:99 and 99: 1, preferably 1: 9 and 9: 1. It depends on this ratio whether alkylphenyl carbonate or diaryl carbonate predominates in the end product.
• the alkylaryl carbonate formed in addition to diaryl carbonate can be separated off by distillation without difficulty and either reacted with fresh phenol or, after the diaryl carbonate has been separated off, can react further with the phencl still present.
• the reaction temperatures are preferably in the range from 50 to 250 ° C., particularly preferably in the range from 100 to 200 ° C. It is advantageous to work at a pressure of 1 torr to 20 atm abs, preferably 1-5 atm.
• Solvents such as aliphatic or aromatic hydrocarbons can also be used.
• a preferred procedure is to bring the transesterification mixture to the desired reaction temperature in a longer column, while the alcohol is removed overhead, to the extent that it is released in the reaction mixture, if appropriate with the aid of an inert gas stream.
• excess dialkyl carbonate is passed through a melt of the phenol to be reacted, while a mixture consisting of the alcohol and dialkyl carbonate is continuously distilled off.
• the components can be separated in a separate step using customary methods.
• the process products can be used as starting materials for the production of polycarbonates by known processes or of crop protection agents.
• the yield based on the converted phenol, is thus 96% of theory. Th. During the reaction, 0.014 mol of CO 2 are split off. This corresponds to a loss of carbonate of 1.05%.
• the reaction product is colored deep red-brown before distillation. Even after the distillation, the diphenyl carbonate still shows a red-brown tinge.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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Citations (4)

• 1977
  • 1977-08-10 DE DE19772736062 patent/DE2736062A1/de not_active Withdrawn
• 1978
  • 1978-08-02 EP EP78100570A patent/EP0000879B1/fr not_active Expired
  • 1978-08-02 DE DE7878100570T patent/DE2860235D1/de not_active Expired
  • 1978-08-08 IT IT50656/78A patent/IT1106869B/it active
  • 1978-08-09 JP JP9628078A patent/JPS5448733A/ja active Pending

Patent Citations (4)

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