SU732242A1 - Method of preparing c2-c10 aliphatic dicarboxylic acid dimethyl esters - Google Patents

Description

This invention relates to organic synthesis, specifically to a process for the preparation of diesters of aliphatic dicarboxylic acids, which are used as plasticizers, low-temperature lubricants, and also raw materials for producing high-quality synthetic nylon-type fibers.

It is known that dimethyl ester of dicarboxylic acid is obtained during the electrolysis of individual monoesters with a yield of 80-85%. Thus, the electrolysis of adipic acid monomethyl ester yielded a yield of sebacic dimethyl ester of about 85% 1, while the electrolysis of glutaric acid monomethyl ester produced cork dimethyl ester with a yield of 78-80% 2.

A known method for the preparation of the dialkil ethers of higher normal dicarboxylic acids is that the ternary mixture of methomethyl esters C -Cg is subjected to electrolytic condensation ::: ation. The process is carried out in methanol at a temperature of 60-65-C and a current density of 1030 A / dm As a result of electrolysis, a mixture of n-carboxylic acid diesters of composition Cg-C is obtained with a total yield of about 76% 3.

The closest in technical essence and the achieved result is a method of obtaining diesters of shifaticheskikh dicarboxylic acids

10 by electrolysis of a methanol solution of an alkali salt of dicarboxylic acid monoesters in the presence of ethylene under pressure at 60-80 ° C, pressure. 60-64 atm and current density of 0.2 15 10 A / dm. The yield of the target product is 92% 4.

The disadvantages of the method are the presence in the target product of low molecular weight by-products,

20 formed with a yield of 5-30% and representing, mainly, esters of saturated and unsaturated monocarboxylic acids. The isolation and disposal of these products represents

Claims (4)

25 great technical difficulties and economically inefficient. In addition, to carry out such a process, a stage is needed for the puluetrification of the lower dicarboxylic acid and the sparing of the alkali salt of the half ester, which leads to the accumulation of by-products in the reaction medium, which complicates the technological scheme. The purpose of the invention is to simplify and increase the selectivity of the process. The goal is achieved. We consider that oxalic acid is used as the oxygen-containing compound, the process is carried out at a density of t; about 0.2-0.7 A / dm. The yield of the target product is 97-99%. . . Oxalic acid differs from other dicarboxylic acids in that the dissociation constants of the first and second stage are significantly different {in water K 5,3b-102, Kjy 5.42-10), while for other dicarboxylic acids these constants are close (for example, for succinic acid, K., 211 Kij 2, 3 S). Thanks to this alkaline acid, in concentrated ethanolic solutions, the monobasic acid is strong. In the process of oxidation, the COOH radical forms at the anode, which in the presence of ethylene under pressure produces adducts — amber, sebacinic, cork, and adipic acids 2COOHHPCH2; CH2; HOOS (CH, COOH. Due to the significant acidification of the solution in the anode space, d carboxylic acids undergo self-arbitrary esterification with the formation of methyl diesters. As a result, the reaction products are oxalic, succinic, corky, adipic, sebacic acid diesters. No other substances ( no by-products) is not formed. The total yield of diesters of amber, adipic, cork, sebacic acids exceeds 95% based on the consumed oxalic acid. The oxalic acid diester is easily washed and Levic acid returns to the cycle again. The detritus of each component is produced by conventional methods, for example, by distillation, which does not represent difficulty, since the difference in the boiling points of the homologues is quite high (20 or more than 1 radius). The costs are small, as rectification Qi is a cheap method of separation, the diester of succinic acid is separated from the mixture and is either used as a final product or is converted to diesters of higher acids (it is converted into monoesters in the usual way, and then converted ayut in higher diesters of diacids obtained with diesters of adipic, suberic acid, sebacic acid and higher acids are used as plasticizers or subjected to the in polyesters or polyamides by conventional means. The use of the proposed method makes it possible to obtain diesters of higher dicarboxylic acids directly from oxalic acid, mine the stage of semi-certification. At the same time, there are no ballast impurities in the target products — esters of saturated and unsaturated monocarboxylic acids, the extraction of which is a great difficulty. Example 1 Electrolysis is subjected to 500 ml of a methanol solution containing 38 mmol (4.75 g) of oxalic acid, which is in a stainless steel autoclave in the atmosphere. ethylene (6064 atm). The current density at the anode is 0.7 A / d1m. The anode is a platinum plate with an area of 10 cm, the cathode is a nickel plate. The electrolyte is vigorously stirred with a magnetic stirrer. The amount of electricity is passed through the electrolyte - 1.55 Ah. Process temperature is 20-25 ° C. The electrolysis product is treated in the following manner. First methanol is distilled off, then the residue is dissolved in water, treated with ethyl ether, the ether extract is dried and the ether is distilled off. The electrolyzate contains oxalic acid and a mixture of diesters of oxalic, succinic, adipic, cork and sebacic acids in the amount of, respectively, 7.0 mol (0.88 g), 9.0 mol (1.06 g), 3.66 mmol (0.535 d), 4.62 mmol (0.805 g), 1.83 mmol (0.37 g) and 0.59 mmol (0.134 g). The total solids content of the last four products per consumed oxalic acid is 97%. Analytical separation and identification of ethereal dicarboxylic esters is carried out by gas chromatography and NMR. The separation is carried out on a preparative Carlo-ЕгБа chromatograph (stationary phase 25 Q F - 1 on glymalite), the initial temperature, then heating up to a speed of 5 deg / min. All 2 peaks coincide with the control. . Peak 1 - dimethyl ester of succinic acid. T. kip. Product 194-195 С (according to the method of Sivolobov in the capillary). NMR spectrum: two signals (f 2.35 and 3.40, ratio 2: 3. Peak 2 - adipino dimethyl ester of your acid. The product boiling point is 229231 ° C. NMR spectrum: three signals cf 1.49, 2 , 09 (broadened) and 3.37, 2: 2: 3 ratio. Peak 3 - cork acid dimethyl ester. T. boiling point product 2632b5 Co NMR spectrum: four signals (f 1.22, 1.45, 2.09 (all wide) and 3.37, 2: 2: 2: 3 ratio. Peak 4 is Sabacinic dimethyl ester. The product bore is 291,292 ° C. Example 2: 50 ml of a methanol solution are subjected to electrolysis. containing 38 mmol (4.75 g) of oxalic acid. The electrolysis conditions are the same as in example 1 for Anodic current density of 0.2 A / dm was turned off. During the experiment, 1.4 Ah of electricity was missed. After treating the electrolyzate according to the method indicated in Example 1, oxalic acid and oxalic, amber, adi-pin, cork diesters were obtained. and sebacic acids in amounts, respectively, of 6.8 mmol (0.85 g), 9.2 mmol (1.08 g), 2.40 mmol (0.36 g), 4.70 mmol (0.82 2, 80 mmol (0.575 g). O, 95; mmol (0.215 g). The total substance yield of the last four products per consumed oxalic acid was 98.5%. Example 3. A 500 ml methanol solution containing 38 mmol (4.75 g) of oxalic acid is subjected to electrolysis. The electrolysis conditions are the same as in Example 1, except for the anodic current density of 3 A / dm. A total of 1.6 AH electricity is missing. After treatment, the electrolyzate contains oxalic acid and oxalic, succinic, and adipic acid diesters. Corky and sebacic acids in the amount, respectively, of 7.5 mmol (0.94 g), 8.8 mmol (1.03 g), 4.15 mm (0.625 g), 4.8 mol (0.835 g), 1.4 mmo (0.028 g) and 0.45 mmol (0.10 g). The total substance yield of the last four pairs of products is equal to 99.5%. Example 4. Electrolysis is subjected to 50 ml of a methanol solution containing 36 mmol (4.75 g) of oxalic acid. The electrolysis conditions are the same as in example 1, the current density is 10 A / dm. Missing only 1.5 Ah electricity. After treatment, the electrolyzate contains oxalic acid and esters of oxalic acid, succinic, adipic, pithic, sebacic acids in the amount of, respectively, 6.4 mmol (Of80 g), 9.5 mmol (1.12 g), 4.35 mmol (0.655 g), b, 2 mmol (91 g), 1.18 mmol (0.24 g), 0.26 mol (0.06 g). The total substance yield of the last four products is 98.7%. 1. Method for producing dimethyl aliphatic aliphatic dicarboxylic acids, about by electrolysis of a methanol solution of an oxygen-containing compound in the presence of ethylene under a pressure of 60-64 atm at a current density of 0.2-10 A / dm, characterized in that the selectivity of the process, oxalic acid is used as the oxygen-containing compound. 2. Method POP.1, characterized in that the process is carried out at a current density of 0.2-0.7 A / dm. Sources of information taken into account during the examination 1. USSR author's certificate 265881, cl. C 07 C 55/20, 1965. 2. Authors, the certificate of the USSR 355237, cl. C 07 S 69/34, 1970. 3. Authors certificate of the USSR 192187, cl. From 25 to 3/00, 1965. 4. USSR author's certificate number 577255, cl. C 07 C 69/34, 1975 (prototype).