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 dimethyl carbonate and phenols by transesterification.
• 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 of not being very selective, since considerable amounts of carbon dioxide are released in a side reaction.
• DOS 2 528 412 describes a corresponding transesterification process for the production of aromatic carbonic acid esters in the presence of Lewis acids, ie transition metal halides, or the corresponding acyloxy, alkoxy or aryloxy compounds as catalysts. If dimethyl carbonate is used as the starting material, then a complex cleaning and separation operation must be carried out to obtain pure dimethyl carbonate (USP 3 803 201, DBP 2 450 856 and OLS 2 607 003), since in the known production processes of dimethyl carbonate (USP 2 642 858 and DOS 2 615 665) an approximately 30% by weight azeotrope with methanol is obtained.
• the task was therefore to find a transesterification process which allows the use of this azeotrope or another mixture of dimethyl carbonate and methanol.
• concentration of dimethyl carbonate in methanol is in the range from 95 to 10% by weight.
• the technically important 30% by weight azeotrope is preferred.
• the invention therefore relates to a process for the preparation of aromatic carbonic acid esters by transesterification of dimethyl carbonate with phenols with the elimination of methanol in the presence of transesterification catalysts, which is characterized in that mixtures of dimethyl carbonate / methanol and methanol-immiscible azeotrope formers are used for the transesterification.
• Azeotropic agents suitable according to the invention are preferably saturated aliphatic hydrocarbons with C 5 -C 8 and with boiling points of 40-130 ° C., such as pentane, hexane, heptane, octane and isooctane, and also technical gasoline fractions which predominantly contain the hydrocarbons mentioned, such as petroleum ether , Ligroin and mineral spirits, and mixtures of the hydrocarbons mentioned.
• the azeotroping agents are expediently used at least in an amount which is sufficient to distill over both the methanol introduced with the dimethyl carbonate / methanol mixture and the methanol formed during the transesterification.
• the amount of azeotroping agent to be added can be found in the known tables (e.g.
• Suitable phenols are preferably compounds of the general formula (I) in which X is hydrogen, an alkyl radical with C 1 -C 3 ' a halogen atom, preferably chlorine, or a nitro group and n is 1 or 2, phenol, o, m, p-cresol, o, m, p are particularly preferred -Chlorphenol, o, m, p-ethylphenol, o, m, p-propylphenol, o, m, p-nitrophenol, 26-dimethylphenol, 2,4-dimethylphenol or 3,4-dimethylphenol used.
• X is hydrogen, an alkyl radical with C 1 -C 3 ' a halogen atom, preferably chlorine, or a nitro group and n is 1 or 2
• phenol, o, m, p-cresol, o, m, p are particularly preferred -Chlorphenol, o, m, p-ethylphenol,
• the known Umestimiskata- l y catalysts can be used. These are preferably alkali metal compounds such as lithium, sodium, potassium hydroxides, alcoholates, phenolates, carboxylates and carbonates , Phenoxytriethyltin, dimethyldibutyltin, dimethyltin glycolate, diethoxydibutyltin, diphenoxydibutyltin, dimethoxydiphenyltin, triethyltin hydroxide, triphenyltin hydroxide, hexaethylstannoxane, hexabutylstannoxane, tetrabutyltinoxhen, tetrabutyltinoxhen, tetrabutyltinoxhen, tetrabutyltinoxhen, tetrabutyltin dophen,
• alkali metal compounds such as lithium, sodium, potassium hydroxides, alcoholates, phenolates, carboxylates and carbonates
• the catalysts are used in concentrations of about 0.001-20% by weight, based on the total amount of reaction.
• the weight ratio of dimethyl carbonate: phenol can vary within wide limits and can be between about 1:99 and 99: 1, preferably 1: 9 and 9: 1. It depends on this ratio whether arylphenyl carbonate or diaryl carbonate predominates in the end product.
• the methylaryl carbonate formed in addition to diaryl carbonate can be separated off without difficulty by distillation and either reacted with fresh phenol or, after the diaryl carbonate has been separated off, recycled for further reaction.
• the reaction temperatures are preferably in the range from 50 to 250 ° C., particularly preferably from 100 to 200 ° C. It is advantageous to work at a pressure of 1 Torr to 20 Atms, preferably 1-5 Atms.
• the preferred procedure is to bring the transesterification mixture to the desired reaction temperature in a longer column, to separate the methanol to the extent that it is released in the reaction mixture, together with the azeotrope, if appropriate with the aid of an inert gas stream, and to dimethyl carbonate with the azeotrope in the Measurements of how the reaction material is depleted of both substances to be fed to the lower part of the column.
• the process products can be converted to polycarbonates in a known manner or serve as starting materials for crop protection agents.
• a total of 340 g of dimethyl carbonate / methanol azeotrope with 400 g of heptane corresponding to 1.13 mol of dimethyl carbonate are used in this way.
• the reaction mixture is fractionated over a 1 m high column.
• dimethyl carbonate and heptane go forward at 69 - 74 ° C / 8 Torr 887 g of non-reacted phenol, in 83 160 0 C / 8 Torr 32.5 g of diphenyl carbonate.
• the yield of aromatic carbonates, based on the converted phenol, is therefore 94% of theory. Th.

Landscapes

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

Applications Claiming Priority (2)

Publications (2)

Family

ID=6016077

Family Applications (1)

Country Status (5)

Cited By (11)

Families Citing this family (27)

Citations (2)

Family Cites Families (4)

• 1977
  • 1977-08-10 DE DE19772736063 patent/DE2736063A1/de not_active Withdrawn
• 1978
  • 1978-08-02 DE DE7878100571T patent/DE2860326D1/de not_active Expired
  • 1978-08-02 EP EP78100571A patent/EP0000880B1/fr not_active Expired
  • 1978-08-08 IT IT7850655A patent/IT7850655A0/it unknown
  • 1978-08-09 JP JP9628178A patent/JPS5448732A/ja active Pending
• 1980
  • 1980-01-10 US US06/110,942 patent/US4252737A/en not_active Expired - Lifetime

Patent Citations (2)

Also Published As

Similar Documents

Legal Events