RU2024494C1 - Process for preparing n-isobornylacrylamide - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: the product: N- isobornylacrylamide, m.p. 137 C. Reagent 1: camphene. Reagent 2: acrylonitrile. Reaction conditions: in CH₃COOH and H₂SO₄ ar a camphene to acrylonitrile to H₂SO₄ to CH₃COOH molar ration of 1: (1.0-1.1):(1.2-1.3):(3-3.5) at 45-55 C for 4-6 hours followed by neutralization of NaOH+H₂O to pH 11-12, extraction of the amide with an organic solvent, washing the extract with a 40-60% aqueous diethanolamine solution at a diethanol solution to amide extract volumetric ration of 1:(5-20) followed by crystallization of the desired product. EFFECT: greater efficiency of the process. 1 tbl

Description

 The invention relates to a method for producing N-isobornylacrylamide by reaction of camphene with acrylonitrile in the presence of sulfuric acid.

 N-isobornyl acrylamide can be used as a monomer to obtain polymer compositions for coating polyolefins with good adhesion [1], as a crosslinking agent [2]. In addition, it is an intermediate product of the production of N-isobornylamine, which is used to obtain drugs [3,4].

 A known method of producing N-isobornylacrylamide by the reaction of camphene with 2 moles of acrylonitrile in the presence of four moles of sulfuric acid in a medium of fifty-fold excess of acetic acid [3]. According to this method, the reaction mass is stirred for 20 hours at room temperature, after which it is poured into cold water. The product was extracted with chloroform, the solution was evaporated, and the precipitated amide was recrystallized from hexane.

 The disadvantages of this method include the duration of the synthesis, the loss of amide due to extraction from an acid solution and the low quality of the resulting product, which is expressed in the fact that the amide, even after recrystallization from an organic solvent, hexane, has a brown color, which limits its use as a monomer. The amount of colored impurities was evaluated by the optical density of a solution of amide in dimethylformamide with a concentration of 5% at a wavelength of 400 nm.

 The aim of the invention is to reduce the synthesis time, reduce amide losses during isolation and purification and improve the quality of the resulting product.

 This goal is achieved by the fact that the reaction is carried out at a molar ratio of reactants close to stoichiometric, namely camphene: acrylonitrile: sulfuric acid: acetic acid = 1: (1-1.1) :( 1.2-1.3) :( 3-3.5) at 45-55 ° C for 4-6 hours, then the reaction mass is neutralized with an aqueous alkali solution to a pH of 11.0-12.0, and the amide extract in an organic solvent, toluene, is washed with an aqueous solution of diethanolamine with a concentration of 40 -60% at a volume ratio of diethanolamine: amide extract 1: (5-20).

 Comparison of the claimed technical solution with the prototype made it possible to establish compliance with its criterion of "novelty." In the study of other well-known technical solutions in this technical field, the features that distinguish the claimed invention from the prototype were not identified and therefore they provide the claimed technical solution with the criterion of "significant differences".

 The method is as follows.

 Acrylonitrile is added to a mixture of concentrated sulfuric and acetic acid cooled to 15 ° C at a temperature not exceeding 20 ° C. A solution of camphene in acetic acid is added to the same mixture in portions at a temperature not exceeding 30 ° C. Then the reaction mass is stirred at a temperature of 45-55 ° C for 4-6 hours. After that, the mixture is neutralized with an alkali solution to pH = 11.0-12.0. Amide from the mixture is extracted with an organic solvent, toluene, and the extract is washed with an aqueous solution of diethanolamine with a concentration of 40-60% at a volume ratio of diethanolamine solution: amide extract 1: 5 - 20.

 The product obtained by mixing camphene, acrylonitrile, sulfuric acid, is a very viscous mass. When diluted with 3-3.5 moles of acetic acid, the reaction mass becomes sufficiently mobile for its mixing and transportation.

 The use in the reaction of more than 3-3.5 moles of the amount of solvent, as in the prototype, leads to a decrease in the reaction rate, as well as to significant losses at the isolation stage. Reducing the amount of solvent from 50 to 3.0-3.5 moles per 1 mol of camphene and a simultaneous increase in temperature from 20-25 ° C to 45-55 ° C reduces the synthesis time from 20 to 4-6 hours. By the synthesis time we mean the time of exhaustion camphene before the conversion of 99.0%. The amide yield is calculated from camphene, because he is usually taken in shortage. The camphene content in the mixture is determined by gas-liquid chromatography of the neutralized reaction mass.

 Reducing the amount of sulfuric acid from 4 to 1.2-1.3 mol per 1 mol of camphene and at the same time reducing the synthesis time from 20 to 4-6 hours can reduce the likelihood of adverse reactions leading to the formation of colored impurities in the amide.

 Carrying out this reaction at a temperature above 55 ° C leads to a strong resinification of the reaction mixture. Colored impurities are sulfonated products and have acidic properties. Therefore, it is advisable to bind them with a base. To isolate the amide from the reaction mixture, it is neutralized with an alkali solution to a pH of 11.0-12.0. With a decrease in pH, the solubility of the amide in the mother liquor increases, because amide is a weak base. In addition, at a lower pH value, a significant amount of acetic acid enters the extract, which entails an increase in the solubility of impurities in the extractant. Increasing the pH value of more than 12.0 does not lead to a decrease in losses and an increase in the quality of the resulting product. The concentration of the alkali solution is selected so that the salt formed during neutralization is in solution and does not precipitate with the amide, i.e. this will complicate the technology. Compared with a simple dilution of the reaction mass with water, where the acidic medium actually remains, the salt formed during neutralization pushes the amide out of solution. Thus, losses during the separation of amide from the mixture are reduced. To remove the remaining impurities, the amide from the aqueous solution is extracted with toluene at 85 ° C, followed by washing the extract with an aqueous solution of diethanolamine with a concentration of 40-60% in a volume ratio of diethanolamine: amide extract 1: 5-20. The use of a diethanolamine solution with a concentration of less than 40% does not allow the amide to be purified efficiently, since the solubility of impurities in the solution decreases. And at a concentration of diethanolamine solution above 60%, the solubility of the amide in it increases, which leads to the loss of amide. Washing the extract with an amount of diethanolamine solution greater than 1 volume per 5 volumes of extract does not lead to further improvement in the quality of the amide.

 PRI me R 1 (prototype). A mixture of 136 g (0.01 M) camphene and 1.06 g (0.02 M) acrylonitrile is added to a cooled mixture of 2.28 ml (0.04 M) concentrated sulfuric acid and 30 ml (0.52 M) glacial acetic acid with stirring . Stirring is continued for 20 hours at room temperature, after which the mixture is poured into 200 ml of cold water. N-isobornylacrylamide is extracted from the mixture with chloroform. Chloroform was evaporated from the solution, the precipitated amide was recrystallized from hexane. Obtain 1.01 g of amide, so pl. = 137 ° C, the optical density of a 5% solution in dimethylformamide at a wavelength of 400 nm = 0.96. Yield 49%.

 Example 2 36.6 ml (0.64 M) of glacial acetic acid and 20.55 ml (0.36 M) of concentrated sulfuric acid were placed in a reactor. After cooling the mixture to 15 ° C, 16 g (0.3 M) of acrylonitrile are added, keeping the temperature not higher than 20 ° C. A solution of 37.5 g (0.275 M) camphene in 17.16 ml (0.3 M) of glacial acetic acid is added in portions at a temperature not exceeding 30 ° C. Thus, the molar ratio of camphene: acrylonitrile: sulfuric acid: acetic acid = 1: 1.1: 1.3: 3.4. Then the reaction mass is stirred at 50 ° C for 5 hours. After this, the mixture is neutralized with 350 g of a 20% sodium hydroxide solution to pH = 12.0, and the amide is extracted from the mixture with 150 ml of toluene at 85 ° C. The extract is washed with 38 ml of a 50% aqueous diethanolamine solution, which corresponds to a volume ratio of diethanolamine: amide extract of 1: 5. The resulting solution is cooled and crystallized. The precipitated amide is filtered and dried. 36.43 g of amide are obtained, yield 64% mp = 137 ° C, light transmission of a 5% solution in dimethylformamide at a wavelength of 400 nm is 0.03.

 Examples 3-6 are carried out analogously to example 2.

 The data are given in the table.

Thus, the reaction of the proposed method allows you to:
reduce the synthesis time from 20 to 4-6 hours;
reduce amide losses during isolation, resulting in an increase in yield from 49% to 61.5 - 64.7%;
to improve the quality of N-isobornylacrylamide, which is reflected in a decrease in the optical density of a 5% solution of amide in dimethylformamide from 0.96 to 0.03.

Claims (1)

METHOD FOR PRODUCING N-ISOBORNYLACRYLAMIDE by reacting camphene with acrylonitrile in the presence of acetic acid in the presence of sulfuric acid, followed by neutralization of the reaction mixture, extraction of the amide with an organic solvent and its crystallization, characterized in that, in order to reduce the synthesis time, reduce the loss of the target product and improve its quality , the process is carried out at a molar ratio of camphene: acrylonitrile: sulfuric acid: acetic acid, equal to 1: 1 - 1.1: 1.2 - 1.3: 3 - 3.5, at 45 - 55 ^o C for 4 - 6 h, carrying out neutralization an aqueous alkaline solution to pH 11 - 12, and the extract was washed with an aqueous solution of diethanolamine having a concentration of 40 - 60% at a volume ratio of solution of the amide of diethanolamine and extract 1: 5 - 20.

Images