CS254629B1 - Process for preparing 2,4,4,4-tetrachlorbutyric acid - Google Patents

Abstract

Process for preparing 2,4,4,4-tetrachlorobutyric acid that is, the ester 2,4,4,4-tetrachlorobutyric acid of formula C13CCH2CHClCOOR where R is to C3 alkyl, such as methyl, ethyl, n-propyl or 2-propyl, is subjected to transesterification reaction with acid formic or acetic acid in the presence catalytic amount of mineral acid sulfuric acid or strong organic acids of the p-toluenesulfonic acid type or an ion exchanger in H + form or mixtures thereof preferably in the presence water by heating the resulting mixture boiling at 60 to 140 ° C, preferably at 100-120 ° C with simultaneous removing the resulting acid ester formic acid or acetic ester. 2,4,4,4-tetrachlorobutyric acid is important intermediate for the production of derivatives dimethylcyclopropanoic acids called synthetic pyrethroids that are highly effective insecticides found wide use in resources plant protection products.

Description

The invention relates to a process for the production of 2,4,4,4-tetrachlorobutyric acid, which is an important intermediate in the manufacture of pyrethroid-type synthetic insecticides.

Pyrethroids, both naturally occurring and synthetic cyclopropanecarboxylic acid derivatives, have long been of interest as insecticides because they are highly effective against a broad spectrum of insects. Pyrethroids exhibit relatively low toxicity to warm-blooded animals, are characterized by increased photostability, while leaving no harmful residues. Their excellent insecticidal properties are described, for example, in Nature 1973, 169,

244, 256, 456.

One possibility for the synthesis of cyclopropanecarboxylic acid derivatives is the conversion of the acid

2.4.4.4-tetrachlorobutyrate by means of cyclobutane and cyclopropane ring intermediates (Helv. Chim. Acta 63, 1947 (1980)). 2,4,4,4-tetrachlorobutyric acid is usually prepared by the free radical addition of carbon tetrachloride to acrylic acid in the presence of copper (I) chloride in acetonitrile with a yield of 79 i. The disadvantage of this procedure is that it is necessary to work at elevated temperatures and pressures h, 115 ° C) and, in addition, 4,4,4-trichlorobutyric acid is also produced as a by-product in an amount of 5-7%.

Alternatively, 2,4,4,4-tetrachlorobutyric acid can be prepared by hydrolyzing its esters which are readily available by the free radical addition of carbon tetrachloride to acrylic esters in high yields (Helv. Chim. Acta., 3, 1947 (1980), CS (PV 2608-86). For example, 2,4,4,4-tetrachlorobutyric acid was obtained by acid hydrolysis of the methyl ester by long-term boiling in hydrochloric acid at atmospheric and elevated pressure (100 to 115 ° C,

h) (J. Chem. Soc. 1963,1887; Helv. Chim. Acta 63,1947 (1980)). Alkaline ester hydrolysis cannot be used to prepare 2,4,4,4-tetrachlorobutyric acid, as the skeleton of the desired product is destroyed.

A simple, industrially applicable and waste-free method of converting esters to acids

2.4.4.4-tetrachlorobutyric catalyzed transesterification reactions are described in the present invention.

The present invention provides a process for preparing 2,4,4,4-tetrachlormáselné consisting in the fact that ester of 2,4,4,4-tetrachlormáselné of formula CI ₃ CCH ₂ chcicoor wherein R is C, to C ₃ alkyl, such as is methyl, ethyl, n-propyl or 2-propyl, is subjected to a transesterification reaction using formic acid or acetic acid in the presence of a catalytic amount of a mineral acid of the sulfuric acid type or a strong organic acid of the p-toluenesulfonic acid type or ion exchanger in H form; mixtures thereof, preferably in the presence of water, by heating the resulting mixture to boiling at a temperature of 60 to 140 ° C, preferably at 100 to 120 ° C while removing the resulting formic ester or acetic acid ester.

2,4,4,4-Tetrachlorobutyric acid is obtained by the transesterification reaction of its esters according to the invention in almost quantitative yield with a purity of min. 99%. The catalyst, which is preferably a non-volatile inorganic or organic acid, does not need to be removed prior to product isolation by distillation under reduced pressure, since 2,4,4,4-tetrachlorobutyric acid is acid-stable, such as sulfuric acid, which remains isolation of the product by distillation and is suitable for reuse. In the case of the volatile nature of the catalyst, or if it is desired to be removed from the reaction mixture, a catalytic amount of acid, generally 1% by weight, is suitable. to the starting ester, neutralized. Suitable neutralizing agents are, for example, alkali metal carbonates such as Na ₂ CO ₃ , KHCO ₃ , NaHCO ₃ , CaCO ₃ or CaO and the like. Particularly advantageous for the industrial performance of the catalysis of the transesterification reaction is the use of an acidic ion exchanger which can be easily separated by filtration and, moreover, allows a continuous process to be carried out.

It is advantageous to carry out the catalytic transesterification reaction in the presence of water or water. dilute acetic acid or dilute formic acid, since the presence of water accelerates the reaction by facilitating removal of the resulting ester, i.e., acetate or formate in the form of an azeotrope. A rectification column of 3 to 5 theoretical plates is sufficient for its separation.

The conversion of 2,4,4,4-tetrachlorobutyric acid esters to the free acid by the transesterification reaction according to the invention is far more advantageous and simpler than previously known processes, including its ease of application in industrial practice as waste-free technology.

These examples further describe a process for the preparation of 2,4,4,4-tetrachlorobutyric acid without limiting or limiting its scope.

Example 1

A mixture of 50.8 g of 2,4,4,4-tetrachlorobutyrate, 60 g of acetic acid, 10 g of water and 1 g of 93% sulfuric acid is heated to boiling for 8 hours while removing the resulting ethyl acetate on the rectification column. 5 TP. By distillation of the reaction mixture under reduced pressure, 44.18 g of 2,4,4,4-tetrachlorobutyric acid of b.p. 104 ° C / 133 Pa with a yield of 97.8% and a purity of 99.8%. The distillation residue was 0.97 g sulfuric acid.

Example 2

A mixture of 101.6 g of 2,4,4,4-tetrachlorobutyrate, ethyl acetate, 135 g of acetic acid, 34 g of water and 4.3 g of p-toluenesulfonic acid monohydrate is heated to boiling for 6 h while removing the resulting ethyl acetate. After neutralization of p-toluenesulfonic acid with sodium bicarbonate and evaporation of the diluted acetic acid, 86.7 g of 2,4,4,4-tetrachlorobutyric acid were isolated by distillation under reduced pressure in a yield of 96%.

Example 3

(a) A mixture of 101,6 g of 2,4,4,4-tetrachlorobutyrate, ethyl acetate, 135 g of acetic acid, 34 g of water and 50 g of Ostion KSC 1 converted to H form (dry matter content 17,5 g) is heated to boiling point. for 12 h while removing the resulting ethyl acetate. After cooling the reaction mixture, the solid ion exchanger was separated by filtration and 83.5 g of 2,4,4,4-tetrachlorobutyric acid were isolated by distillation of the filtrate under reduced pressure in a yield of 92.5%.

b) The transesterification reaction was repeated in the same manner as in Example 3a, except that the unwashed ion exchanger used in Example 3a was fed into the reaction mixture and 90.1 g of 2,4,4,4-tetrachlorobutyric acid was recovered in the same manner in a yield of 99%. , 7%.

Example 4

A mixture of 50.8 g of 2,4,4,4-tetrachlorobutyrate, ethyl acetate, 54.1 g of 85% formic acid and 1 g of sulfuric acid is heated to boiling for 7.5 h while removing the resulting ethyl acetate. In the same manner as in Example 1, 43.5 g of acid are isolated

2,4,4,4-tetrachlorobutyrate with a yield of 96,3% and a purity of 99,7%.

Example 5

A mixture of 96 g of 2,4,4,4-tetrachlorobutyrate butyrate, 96 g of acetic acid, 17 g of water and 0.4 g of sulfuric acid is heated to boiling for 13 h while removing the resulting methyl acetate. By working up the reaction mixture as described in Example 1, 88.1 g of 2,4,4,4-tetrachlorobutyric acid are isolated in a yield of 97.5% with a purity of 99.6%.

Claims (4)

SUBJECT OF THE INVENTION A process for the preparation of 2,4,4,4-tetrachlorobutyric acid, characterized in that the acid ester The 2,4,4,4-tetrachlorobutyric formula of the formula C1-4CH2CHClCOOR wherein R is to alkyl such as methyl, ethyl, n-propyl or 2-propyl is subjected to a transesterification reaction using formic acid or acetic acid in the presence of a catalytic amount of a mineral acid of the sulfuric acid type or of a strong organic acid of the p-toluenesulphonic acid type or of an ion exchanger in H ⁺ form or a mixture thereof preferably in the presence of water by heating the resulting mixture to boiling at 60 to 140 ° C, preferably at 100 to 120 ° C while removing the formic acid ester or acetic acid ester formed. 2. Process according to claim 1, characterized in that it is used per 1 molar part of the acid ester 2,4,4,4-tetrachlorobutyric acid 1 to 20 parts by mol of formic acid or acetic acid at a concentration of 50 to 100% by weight. 3. The process of claim 1 wherein concentrated formic acid or concentrated acetic acid is used and up to 0.5 parts by weight of water per 1 part by weight of formic acid or acetic acid is added to the reaction mixture. 4. A process according to claim 1, characterized in that it is used per mole part of the acid ester 2,4,4,4-tetrachlorobutyric acid 0.001 to 0.1 molar parts of sulfuric acid or phosphoric acid, or perchloric acid or nitric acid or p-toluenesulfonic acid or up to 3 parts by weight of an ion exchanger containing an SO4H group.