RU2394810C2 - Method of producing 21,4,41 -trinitrobenzanilide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to organic chemistry and a method of producing 2¹,4,4¹ -trinitrobenzanilide (TNBA), a semiproduct of 5(6)-amino-2-(4-aminophenyl)benzimidazole synthesis, used as monomer in production of heat resistant and high-strength fibre. TNBA is obtained through acylation of 2,4-dinitroaniline with 4-nitrobenzoyl chloride using iron chloride as a catalyst while heating in a medium of an organic solvent in the presence of anhydride of 4-nitrobenzoic acid with extraction of TNBA through crystallisation, filtration and subsequent neutralisation with ammonia in an aqueous suspension, where the reaction mother solution formed after crystallisation and filtration is returned for recycling in the next acylation process. Anhydride of 4-nitrobenzoic acid is obtained by pre-heating 4-nitrobenzoyl chloride which contains an admixture of 4-nitrobenzoic acid in an organic solvent medium. The acylation process is combined with distillation of a portion of the solvent. The reaction mother solution is treated with activated carbon before recycling.

EFFECT: method prevents intense release of hydrogen chloride during the initial period of the reaction, considerably cuts on amount of wastes, reduces consumption of raw material and increases TNBA output.

4 cl, 15 ex

Description

The present invention relates to the field of organic chemistry and relates to a method for producing 2 ′, 4,4′-trinitrobenzanilide, an intermediate of the synthesis of 5 (6) amino-2- (4-aminophenyl) benzimidazole, used as a monomer in the production of heat-resistant and high-strength fibers.

A known method for producing 2 ′, 4,4′-trinitrobenzanilide (hereinafter TNBA) by acylation of 2,4-dinitroaniline with 4-nitrobenzoic acid in the presence of an activator - polychlorocyclophosphazene and a catalyst - N-oxides of pyridine or β- and γ-picoline in a medium of chlorobenzene with subsequent isolation of the target product by distillation of chlorobenzene with water vapor (a.s. of the USSR 1025093, С07С 233/66, publ. 02.20.1999). The disadvantage of this method is the use of inaccessible activator and catalysts.

A known method of producing TNBA by nitration of N- (4′-nitrobenzoyl) aniline with nitric acid in a concentrated sulfuric acid medium (US patent 4109093, NCI US 548 / 310.7, publ. 08/22/1978). The main disadvantage of this method is the large amount of waste - a mixture of concentrated sulfuric and nitric acids contaminated with impurities of organic substances.

The closest analogue of the proposed method for producing TNBA (prototype) is a method based on the acylation of 2,4-dinitroaniline with 4-nitro-benzoyl chloride in a solvent of a series of chlorobenzene, paraxylene, a technical mixture of xylenes, toluene or ethylbenzene when heated in the presence of ferric chloride (FeCl ₃ ) as a catalyst with the release of TNBA from the reaction mass by crystallization, filtration of the resulting suspension and subsequent neutralization with aqueous ammonia (RF patent 2283307, C07D 235/18, publ. 09/10/2006).

The disadvantages of this method are:

1. The low solubility of ferric chloride in the reaction mass in the initial period of synthesis, leading to the presence of an induction period, and then to too rapid a process with the evolution of hydrogen chloride, which complicates its capture.

2. The formation of large amounts of waste (organic solvent containing aromatic nitro compounds) that pollute the environment. In this case, the reagents and product (TNBA) dissolved in the mother liquor are lost.

The objective of the present invention is to develop a method for producing TNBA, devoid of the disadvantages inherent in the prototype.

The problem is solved by the proposed method for producing TNBA by acylation of 2,4-dinitroaniline (DND) with 4-nitrobenzoyl chloride (PNBH) using ferric chloride as a catalyst when heated in an organic solvent in the presence of 4-nitrobenzoic acid anhydride with the release of TNBA by crystallization, filtration and subsequent neutralization with ammonia in an aqueous suspension, and the reaction mother liquor formed after crystallization and filtration of TNBA is returned to recycling for the next acylation operation.

The proposed method is characterized in that the acylation process is carried out in the presence of 4-nitrobenzoic acid anhydride and the reaction mother liquor formed after crystallization and filtration of TNBA is recycled to the next acylation operation.

The recycling can be carried out an unlimited number of times, while the entire mother liquor or part of it can be returned to the recycling without any processing. If necessary, the mother liquor can be purified by treatment with an adsorbent, for example, activated carbon.

As an organic solvent in the implementation of the proposed process for producing TNBA, solvents can be used that form an azeotrope with water: chlorobenzene, p-xylene, o-xylene, technical mixture of xylenes, ethylbenzene or toluene.

To prevent the accumulation of excess solvent in the reaction mass, which comes with the recycled mother liquor, with a solution of PNBH in the corresponding solvent or with a solution, suspension or paste of DND, part of the solvent is distilled off directly from the acylation reactor during the reaction, combining the acylation and distillation of the solvent into time. As a result, there is no need to use additional equipment for solvent stripping.

The acylation reaction of 2,4-dinitroaniline (DND) with 4-nitrobenzoyl chloride (PNBH) in the presence of ferric chloride in an organic solvent begins to proceed at a noticeable rate even at a temperature of 80-90 ° C and at 100-120 ° C the acylation process in the initial period very intense with the release of hydrogen chloride, which complicates the process of its capture. To prevent too intense evolution of hydrogen chloride and ejection of the reaction mass, the process is conducted in the presence of 4-nitrobenzoic acid anhydride.

4-nitrobenzoic acid anhydride (hereinafter NBA) forms a donor-acceptor complex with a high value of the stability constant with ferric chloride.

Complex Stability constant, dm ³ / mol PNBCH · FeCl ₃ 3.6 4-NBC FeCl ₃ 45.5 NBA FeCl ₃ 200,0

This, on the one hand, increases the solubility of ferric chloride in the reaction mass and, on the other hand, ensures a smooth, uniform reaction.

DND can be introduced into the process in the form of a dry substance or in the form of a paste with the appropriate solvent in which the acylation is carried out, or in the form of an aqueous paste. In the latter case, before adding the mother liquor and PNBH, it is necessary to dehydrate the DND. Dehydration is carried out by azeotropic distillation of water with a solvent.

PNBH can be introduced into the process as a solid or as a solution in an appropriate solvent in which acylation is carried out.

Ferric chloride can be introduced into the process in the form of dry anhydrous ferric chloride FeCl ₃ by loading it directly into the acylation reactor or by adding it to the solution of BNP. Ferric chloride can also be introduced into the process in the form of FeCl ₃ · 6H ₂ O crystalline hydrate or as an aqueous solution by adding it to DND followed by dehydration by azeotropic distillation with a solvent.

4-nitrobenzoic acid anhydride (NBA) can be introduced in the form of a powder or can be obtained and introduced into the acylation process by heating a solution of PNBH in the organic solvent used in the process. In this case, NBA is formed as a result of the interaction of 4-nitrobenzoyl chloride with 4-nitrobenzoic acid present in it as an impurity, usually as 0.2-1.0 wt.%.

In subsequent acylation operations, NBA can be introduced with a recycled mother liquor, in which it is highly soluble.

The implementation of the process according to the proposed method provides a smoother, more uniform acylation process, which prevents too intense evolution of hydrogen chloride in the initial period of the reaction, coupled with the possible release of the reaction mass, simplifies the organization of the process of trapping hydrogen chloride. The proposed method also provides a significant reduction in the amount of production waste, reducing the consumption of raw materials, increasing the output of TNBA.

The invention is illustrated by the following examples.

Example 1

139.7 g of 2,4-dinitroaniline (DND), 162.0 g of 4-nitrobenzoyl chloride (PNBH) are charged into a three-necked flask with a capacity of 2 dm ³ equipped with a stirrer, a reflux condenser connected to a hydrogen chloride recovery system and a thermometer. solid cups, 0.68 g of anhydrous ferric chloride, 1.0 g of 4-nitro-benzoic anhydride (NBA) and 530 g of chlorobenzene.

The reaction mass is heated with stirring. At a temperature of 80 ° C, a uniform evolution of hydrogen chloride begins. The mass is heated to 133-135 ° C and kept in boiling mode for 2 hours. By this time, the evolution of hydrogen chloride is complete.

Next, the reaction mass is cooled to 5-10 ° C, the resulting suspension is filtered on a Buchner funnel, the TNBA precipitate on the filter is washed with 230 g of chlorobenzene. The main and wash filtrates are combined and used in the next acylation operation.

Chlorobenzene is distilled off from the TNBA paste with water vapor, the suspension is cooled to 40-70 ° C and neutralized with a 0.25% ammonia solution to pH 8. The aqueous suspension of TNBA is filtered, washed with water to remove the NSC ammonium salt. 247.2 g of TNBA are obtained (97.5% of theory). Melting point 195 ° C, content,%: DND 0.10; NSC 0.06; The pH of the aqueous extract is 7.0.

Example 2

687 g of a solution of 4-nitrobenzoyl chloride (PNBH) in chlorobenzene containing 163 g of PNBH, 0.5% 4-nitrobenzoic acid, is loaded into a three-necked flask with a capacity of 2 dm ³ equipped with a stirrer, a reflux condenser connected to a hydrogen chloride recovery system and a thermometer. (NSC) and 524 g of chlorobenzene. The solution was stirred at the boil for 2 hours. The conversion of NBA to 4-nitrobenzoic acid anhydride (NBA) is 64%, the amount of NBA formed is 0.987 g. Next, 139.7 g of 2,4-dinitroaniline (DND) and 0.68 g of anhydrous ferric chloride are charged into the flask.

The reaction mass is heated with stirring. At a temperature of 85 ° C, a uniform evolution of hydrogen chloride begins. The mass is heated to 134-135 ° C and given at this temperature in boiling mode exposure for 2 hours to complete the evolution of hydrogen chloride.

Next, the flask is cooled with water, and then in the refrigerator to a temperature of 5-10 ° C and the resulting suspension is filtered on a Buchner funnel with suction using vacuum. The TNBA precipitate was washed with 230 g of chlorobenzene. The main and wash filtrates are combined. Get 740 g of chlorobenzene mother liquor containing, g: DNA 0.48; PNBH 13.4; TNBA 6.63; NSC 2.60; FeCl ₃ 0.34 and NBA 2.62.

Chlorobenzene is distilled off from the TNBA paste with water vapor, the suspension is cooled to 30-70 ° C and neutralized with a 0.25% ammonia solution to pH 8. The aqueous suspension of TNBA is filtered off, washed with water to remove the NSC ammonium salt. 246.5 g of TNBA are obtained (97.2% of theory). Melting point 195 ° C, content,%: DND 0.12; NSC 0.05; The pH of the aqueous extract is 7.0.

Example 3

In the flask described in example 2, load 730 g of the mother liquor obtained in example 2, 139.2 g of DND, 149.77 g of PNBH and 0.48 g of FeCl ₃ . The amount of NBA introduced with the mother liquor is 2.58 g. The reaction mass is heated with stirring to 132 ° C (boiling of the reaction mass) and incubated for 2 hours. In the process of exposure, 80 cm ^{3 of} chlorobenzene are distilled off using a direct refrigerator and combining the processes of solvent distillation and acylation. The temperature in the reaction mass rises to 134-135 ° C. Next, the reaction mass is treated as described in examples 1 and 2. Receive 866 g of chlorobenzene mother liquor containing, g: DND 0.52; PNBH 14.40; TNBA 7.96; NSC 2.34; FeCl ₃ 0.41; NBA 2.72. This mother liquor is used in the next recycle operation (synthesis of TNBA). The TNBA chlorobenzene paste is placed in 1200 ml of water and chlorobenzene is distilled off in the form of an azeotrope with water. TNBA in an aqueous suspension is neutralized with a 0.25% aqueous ammonia solution at a temperature of 50-70 ° C, bringing the medium to a stable pH value of 8. A neutralized suspension of TNBA is filtered and washed with water. The yield of TNBA 250.8 g (99.0% of theoretical). Melting point 194 ° C; content,%: DN 0.2; NSC 0.1; The pH of the aqueous extract is 6.8.

Example 4

In a three-necked flask with a capacity of 2 dm ³ , equipped with a stirrer, a thermometer, a three-horned nozzle with a dropping funnel, a reflux condenser with a direct refrigerator and a receiver, 154.4 g of DND wet paste containing 139.15 g of the basic substance, 1 g of an aqueous solution of FeCl ₃ are charged, containing 0.48 g of ferric chloride and 330 g of chlorobenzene. The contents of the flask are heated with stirring and the water is distilled off in the form of an azeotrope before the start of distillation of anhydrous chlorobenzene. Then the mixture of DND with chlorobenzene in the flask is cooled to 70 ° C with stirring, a reflux condenser is installed in the three-neck nozzle, 840 g of the chlorobenzene mother liquor obtained in Example 3 and containing 0.5 g of DND, 14.0 g of PNBH, 7.7 g are loaded TNBA, 2.3 g of NBA, 0.4 g of FeCl ₃ and 2.64 g of NBA.

The reaction mass is gradually heated with stirring for 1 hour to a boil (132 ° C). Then the reflux condenser is removed and when the reaction mass is boiled and stirred from a dropping funnel for 1.5 hours, 331 g of a 45% solution of PNBH in chlorobenzene containing 148.9 g of PNBH are added.

In the process of adding a solution of PNBH, 630 g of chlorobenzene are distilled off through a reflux condenser and a direct refrigerator. Next, the reaction mass is treated as in examples 1 and 2. Receive 744 g of chlorobenzene mother liquor containing, g: DND 0.6; PNBH 12.1; TNBA 9.6; NSC 1.4; FeCl ₃ 0.39 and NBA 2.4. This mother liquor is sent to the next recycle operation (TNBA synthesis). The TNBA chlorobenzene paste is placed in 1200 ml of water, chlorobenzene is distilled off and neutralized with 0.25% aqueous ammonia. After filtering the aqueous suspension and washing with water, 249.9 g of TNBA are obtained (98.5% of theory). Melting point 194 ° C; content, wt.%: DN 0.2; NSC 0.05; The pH of the aqueous extract is 6.9.

Example 5

680 g of the mother liquor isolated in Example 4 is treated before OU-B activated carbon is introduced into the synthesis of TNBA. To do this, in a three-necked flask with a capacity of 1 dm ³ , equipped with a stirrer, a direct refrigerator and a thermometer, 140 g of OU-B activated carbon water paste containing 75 g of coal in terms of 100% are loaded, 280 g of chlorobenzene are added and 65 ml of water are distilled off in the form of an azeotrope with chlorobenzene until a temperature in pairs of 131 ° C is reached. Next, 680 g of the mother liquor obtained after the synthesis of TNBA in Example 4 was added to the flask. The mass was heated with stirring to 80 ° C, kept for 0.5 hours, cooled to room temperature, then the mother liquor was filtered from coal on a Buchner funnel with suction.

Get 730 g of chlorobenzene mother liquor containing, g: DND 0.52; PNBH 11.3; TNBA 4.7; NSC 1.5; FeCl ₃ 0.29 and NBA 2.1. This mother liquor is sent to the next recycle operation. In the reaction flask, as in examples 1 and 2, 703 g of purified mother liquor containing 0.50 g of DND, 10.7 g of PNBH, 4.5 g of TNBA, 1.4 g of NBA and 2.0 g of NBA are charged. 139.1 g of DND, 151.9 g of PNBH and 0.5 g of ferric chloride are added. Acylation is carried out as described in examples 1-3. 200 g of chlorobenzene are distilled off during boiling. TNBA is isolated and neutralized in an aqueous suspension with 0.25% aqueous ammonia at 50-70 ° C until a stable pH of 8. After filtration and washing with water, 248.8 g of TNBA are obtained (98.2% of theory). Melting point 194 ° C; content, wt.%: DND 0.12; NSC 0.01; The pH of the aqueous extract is 6.8.

Chlorobenzene mother liquor in an amount of 720 g, containing, g: DND 1.1; PNBH 19.8; NSC 2.2; TNBA 7.8; NBA 3.1, used in the next operation of the synthesis of TNBA.

Example 6

The process is carried out with downloads, similarly to example 1, but toluene is used as a solvent, and NBA is introduced directly into the synthesis at the acylation stage. The maximum reaction temperature is 112 ° C. 245.5 g of TNBA (96.9% of theory) are obtained. T pl. 196 ° C, DND content of 0.3 wt.%; NBK and 570 g of toluene mother liquor containing 0.49 g of DND; 13.1 g PNBH; 7.0 g of TNBA; 1.4 g NSC; 0.32 g of FeCl ₃ and 2.1 g of NBA.

Example 7

The synthesis of TNBA is carried out under the conditions of example 6 using 560 g of the toluene mother liquor from example 6. 80 g of toluene are distilled off during the synthesis. 248.8 g of TNBA are obtained (98.2% of theory). Mp 196 ° C, DND content of 0.25 wt.%; NSC 0.25 wt.%; The pH of the aqueous extract is 6.9.

Example 8

The process is carried out with downloads, similarly to example 2, but p-xylene is used as a solvent. The maximum temperature at the stages of NBA synthesis and acylation is 139 ° С. 251 g of TNBA are obtained (99.1% of theory). T pl. 195 ° C, DND content of 0.1 wt.%; NSC Ot .; pH of an aqueous extract of 6.8 and 565 g of p-xylene mother liquor containing 0.45 g of DND; 11.9 g PNBH; 7.8 g of TNBA; 1.8 g NSC; 0.40 g of FeCl ₃ and 2.3 g of NBA.

Example 9

The synthesis of TNBA is carried out under the conditions of Example 8 using 550 g of the p-xylene mother liquor from Example 8. 251 g of TNBA is obtained (99.1% of theory). T pl. 194 ° C; the content of DNA is 0.18 wt.%; NSC Ot .; The pH of the aqueous extract is 6.9.

Example 10

The process is carried out with downloads as in example 2, but o-xylene is used as the solvent. The maximum temperature at the stages of NBA synthesis and acylation is 144 ° С. 244 g of TNBA are obtained (96.3% of theory). T pl. 194 ° C, DND content of 0.32 wt.%; NSC 0.1 wt.%; pH of an aqueous extract of 6.8 and 574 g of an o-xylene mother liquor containing 0.49 g of DND; 12.2 g PNBH; 7.5 g TNBA; 1.5 g NSC; 0.37 g of FeCl ₃ and 2.5 g of NBA.

Example 11

The synthesis of TNBA is carried out under the conditions of Example 10 using 565 g of the o-xylene mother liquor from Example 10. 250.4 g of TNBA are obtained (98.8% of theory). T pl. 194 ° C; DND content of 0.19 wt.%; NSC Ot .; The pH of the aqueous extract is 6.9.

Example 12

The process is carried out with downloads, similarly to example 2, but a technical mixture of xylenes is used as a solvent. The maximum temperature at the stage of NBA synthesis and acylation is 142 ° С. 242.7 g of TNBA are obtained (95.8% of theory). T pl. 194 ° C; DNA content 0.17 wt.%; NSC 0.03 wt.%; pH of an aqueous extract of 7.0 and 540 g of xylene mother liquor containing 0.48 g of DND; 12.0 g PNBH; 8.4 g of TNBA; 1.59 g of NSC; 0.41 g of FeCl ₃ and 2.2 g of NBA.

Example 13

The synthesis of TNBA is carried out under the conditions of Example 12 using 530 g of the xylene mother liquor from Example 12. 249 g of TNBA are obtained (98.3% of theory). T. pl. 194 ° C; the content of DNA is 0.11 wt.%; NSC 0.02 wt.%; The pH of the aqueous extract is 6.8.

Example 14

The process is carried out with downloads as in example 2, but ethylbenzene is used as a solvent. The maximum temperature at the stages of NBA synthesis and acylation is 137 ° С. 242.7 g of TNBA are obtained (95.8% of theory). T pl. 195 ° C; the content of DNA is 0.10 wt.%; NSC 0.01 wt.%; the pH of the aqueous extract of 6.7 and 554 g of ethylbenzene mother liquor containing 0.44 g of DND; 12.9 g PNBH; 7.6 g of TNBA; 1.52 g of NSC; 0.35 g of FeCl ₃ and 2.6 g of NBA.

Example 15

The synthesis of TNBA is carried out under the conditions of Example 14 using 545 g of the ethylbenzene mother liquor from Example 14. 250.3 g of TNBA are obtained (98.8% of theory). T pl. 195 ° C; the content of DNA is 0.14 wt.%; NSC 0.02 wt.%; The pH of the aqueous extract is 6.8.

Claims (4)

1. The method of obtaining 2 ′, 4,4′-trinitrobenzanilide by acylation of 2,4-dinitroaniline 4-nitrobenzoyl chloride using ferric chloride as a catalyst when heated in an organic solvent, with the release of 2 ′, 4,4′-trinitrobenzanilide by crystallization, filtration and subsequent neutralization with ammonia in an aqueous suspension, characterized in that the acylation process is carried out in the presence of 4-nitrobenzoic acid anhydride, and the reaction mother liquor formed after crystallization and filtration is recycled to the next acylation operation. 2. The method according to claim 1, characterized in that the 4-nitrobenzoic acid anhydride is obtained by preheating 4-nitrobenzoyl chloride containing an admixture of 4-nitrobenzoic acid in an organic solvent solution. 3. The method according to claim 1, characterized in that the acylation process is combined with the process of distillation of part of the organic solvent. 4. The method according to claim 1, characterized in that the reaction mother liquor is treated with activated carbon before returning to recycling.