DE3811067C1 - Process for the preparation of 4,4'-bis(carboxybenzoyl)diphenyl ethers - Google Patents

Abstract

4,4'-Bis(carboxybenzoyl)diphenyl ethers can be prepared from diphenyl ether and iso- or terephthalic dichloride, but oligomeric dicarboxylic acids are also obtained in this process. Oxidation of compounds of the structure <IMAGE> allows 4,4'-bis(carboxybenzoyl)diphenyl ethers to be prepared in high purity and high yields. Preparation of 4,4'-bis(carboxybenzoyl)diphenyl ethers.

Description

The invention relates to a process for the preparation of 4,4'-bis (car boxybenzoyl) diphenyl ethers of the structure

Dicarboxylic acids are valuable intermediates for the production of Polyamides, polyesters or plant protection products. In the event of of the polycondensates, aromatic dicarboxylic acids are preferred since these the properties of the polymers such as rigidity, temperature resistance or positively influence resistance to hydrolysis.

DE-OS 19 19 010 uses condensation products of diphenyl ether Iso- or terephthalic acid diesters claimed. The condensation products depend on the molar ratio of the starting materials and the reaction conditions Oligomers of different degrees of condensation. Diesters of dicarboxylic acids of structure I are also claimed. One method of making the dicarboxylic acids themselves is however not specified.

According to Japanese patent specification 74-51 252, diphenyl ether can also be used Iso- or terephthalic acid dichloride in polyphosphoric acid to oligomeric Ketone dicarboxylic acids are implemented. The reaction products can also predominantly contain dicarboxylic acids of structure I.

In the processes mentioned, the reaction products are not products with a defined molecular weight but oligomers with a medium Molecular weight and a molecular weight distribution.

It is also known that alkyl aromatics such as toluene or xylene Can convert oxidation into aromatic carboxylic acids. After B.E. Leach, Applied Industrial Catalysis, Vol. 3, pp. 158 ff. (1984) can  oxidation by oxygen or air at 60 or 65 ° C in the presence of cobalt salts, usually acetic acid is used as a solvent.

For the production of structure I dicarboxylic acids by oxidation the corresponding alkyl or acyl compound is the process however not suitable. Because those in the oxidation as intermediates resulting monocarboxylic acids of the structure

where R is alkyl or acyl, are sparingly soluble and withdrawn therefore further oxidation to the dicarboxylic acids.

The object of the present invention is 4,4'-bis (carboxybenzoyl) - Diphenyl ether of structure I in pure form with a defined molecular weight to manufacture. The products should not contain oligomers be contaminated.

The object is achieved in that connections the structure

where R is alkyl with 1 to 4 carbon atoms, oxidized at 80 to 400 ° C. The oxidation is carried out with oxygen or oxygen-containing Gases in an organic solvent and in the presence of transition metal salts.

The starting compounds of structure II can by methods such as for example, by A. R. Brown and F. C. Copp, Journal of the Chemical Society, 1954, p. 873 ff. And in DE-OS 20 47 370 will be manufactured. In structure II, R is preferably methyl.  

Suitable solvents are e.g. B. carboxylic acids such as acetic acid, propionic acid, Butyric acid, caproic acid, benzoic acid or naphthalene carboxylic acid. Acetic acid or benzoic acid are preferred. Generally will about 2 to 70% solutions of the starting compounds used, wherein 5 to 30% solutions are preferred.

The reaction is preferably carried out at a temperature of 120 to 250 ° C and a pressure of 1 to 50 bar. With increased pressure you can carry out the reaction in an autoclave.

Oxygen or an oxygen-containing gas serves as the oxidizing agent. Pure oxygen or air is preferably used.

Transition metal salts such as cobalt, Manganese, zirconium or cerium compounds or mixtures thereof are added. Cobalt and manganese compounds are preferably used here, with cobalt compounds being particularly preferred. The Catalysts can also be used together with activators such as e.g. B. Alkali or alkaline earth bromides can be used.

According to the inventive method, 4,4'-bis (car boxybenzoyl) diphenyl ether, in which both carboxyl groups either in the p-position or in the m-position.

No oligomeric dicarboxylic acids are obtained by the process according to the invention produced. No intermediate products are formed, which further oxidation to the dicarboxylic acids by precipitation revoke. According to the present method, 4,4'-bis (carboxyben zoyl) diphenyl ether with high purity and defined molecular weight are produced in high yields.

Example 1

9.8 g (0.024 mol) of 4,4′-bis (4-methylbenzoyl) diphenyl ether, 1.2 g of cobalt (II) - Acetate and 0.49 g sodium bromide are mixed in 90 g at 130 ° C Dissolved benzoic acid. At this temperature, it becomes acidic for 8 hours  material flow of 50 l / h passed through the solution. In the course of the reaction the resulting dicarboxylic acid precipitates. The mixture becomes hot filtered and the precipitate washed with ethanol and with water. 11.0 g (98% of theory) of 4,4′-bis (4-carboxybenzoyl) diphenyl are obtained ether.

Melting point: 392 ° C

Elemental analysis:
Ber. C 72.10%, H 3.89%,
Found C 72.10%, H 3.85%.

Example 2

9.8 g (0.024 mol) of 4,4'-bis (3-methylbenzoyl) diphenyl ether, 1.2 g of Ko balt (II) acetate and 0.49 g sodium bromide are dissolved in 120 ml butyric acid dissolved and heated to 130 ° C. At this temperature, be 8 hours long 50 l / h of oxygen passed through the solution. After 8 hours, the mixture starts cooled to room temperature. The precipitated dicarboxylic acid is removed filtered, washed with water and dried. The yield is 10.8 g (97% of theory) of 4,4′-bis (3-carboxybenzoyl) diphenyl ether.

Melting point: 319 ° C

Elemental analysis:
Ber. C 72.10%, H 3.89%,
Found C 72.09%, H 3.77%.

Example 3

A mixture of 40.8 g (0.1 mol) of 4,4'-bis (4-methylbenzoyl) diphenyl ether, 5 g cobalt (II) acetate, 2.06 g sodium bromide and 500 ml acetic acid is placed in a 1 liter Hastelloy autoclave. The autoclave is heated to 200 ° C. 20 bar of oxygen are injected for 20 h. After cooling to room temperature, the autoclave is let down, the batch removed and filtered. The filter cake is washed with acetic acid, Washed water and ethanol and dried. 40.9 g (87.6% d. Th.) 4,4'-bis (4-carboxybenzoyl) diphenyl ether.

Example 4

Analogously to Example 3, 40.8 g (0.1 mol) of 4,4'-bis (3-methylbene zoyl) oxidized diphenyl ether, using compressed air as the oxidizing agent Place of pure oxygen is used. The yield is 40 g (85.6% of theory) of 4,4′-bis (3-carboxybenzoyl) diphenyl ether.  

Comparative Example A

9.8 g (0.024 mol) of 4,4′-bis (4-methylbenzoyl) diphenyl ether, 1.2 g of cobalt (II) - acetate and 0.49 g sodium bromide boil in 90 g Acetic acid dissolved. After cooling to 60 ° C, an oxygen stream becomes 8 h of 50 l / h passed through the solution. In the course of the reaction precipitation occurs. After 8 h the mixture is brought to room temperature cooled down. The resulting precipitate is filtered off and washed with water and ethanol.

Yield: 9.6 g
Melting points: 276 ° C and 319 ° C

According to 1 H-NMR analysis, the precipitate consists of a mixture unreacted starting compound and 4- (4-methylbenzoyl) -4 ′ - (4- carboxybenzoyl) diphenyl ether.

Comparative Example B

According to Comparative Example A, 9.8 g (0.024 mol) of 4,4′-bis (3- methylbenzoyl) subjected to the oxidation of diphenyl ether.

Yield: 8.8 g
Melting points: 216 ° C and 295 ° C

According to 1 H-NMR analysis, the precipitate consists of unreacted Starting compound and from 4- (3-methylbenzoyl) -4 ′ - (3-carboxybenzoyl) - diphenyl ether.

The comparative examples show that the reaction at 60 ° C. is only incomplete runs up to an intermediate of structure III, which fails and is thus removed from further oxidation.

Claims (6)

1. Process for the preparation of 4,4'-bis (carboxybenzoyl) diphenyl ethers of the structure characterized in that compounds of structure where R is alkyl with 1 to 4 carbon atoms, oxidized in an organic solvent at 80 to 400 ° C with oxygen or oxygen-containing gases in the presence of transition metal salts. 2. The method according to claim 1, characterized, that the oxidation in acetic acid or benzoic acid as a solvent carries out. 3. The method according to claim 1, characterized, that one oxidizes at 120 to 250 ° C. 4. The method according to claim 1, characterized, that one carries out the oxidation at a pressure of 1 to 50 bar. 5. The method according to claim 1, characterized, that the oxidation is catalyzed by cobalt and / or manganese salts becomes.   6. The method according to claim 1, characterized, that 4,4'-bis (carboxybenzoyl) diphenyl ether are prepared in which both carboxyl groups in the p-position or both carboxyl groups stand in the m position.