RU2472800C1 - Method of producing hexamethylphosphorotriamide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: disclosed is a method which involves treatment of phosphorus oxychloride with excess dimethylamine in toluene medium, adding the mixture of phosphorus oxychloride and toluene in droplets, raising the reaction temperature, after precipitation of dimethylamine hydrochloride salt, to room temperature and then to 100°C, filtering the salt on a Buchner funnel, distilling toluene from the filtrate in a vacuum, separating hexamethylphosphorotriamide by distillation at pressure of 1.0-1.5 mm Hg, and is characterised by that treatment of phosphorus oxychloride with excess dimethylamine in toluene is carried out in the presence of a catalyst - anhydrous aluminium chloride at temperature of -5…+5°C.

EFFECT: method increases output of pure hexamethylphosphorotriamide and reduces power consumption.

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Description

The invention relates to the field of organic chemistry, in particular to a method for the synthesis of organic phosphorus-containing compounds. Hexamethylphosphoric triamide can be used to dissolve polymers; as a selective solvent of gases; as a catalyst in polymerization processes and to stabilize polystyrene to thermal degradation, as well as polyvinyl and polyolefin to ultraviolet rays; as a solvent in organic and inorganic synthesis and for processing solutions in the synthesis of aromatic polyamide fibers.

A known method of producing hexamethylphosphoric triamide, which consists in the reaction of phosphorus oxychloride and dimethylamine in a medium of hexamethylphosphoric triamide, where it is used as an organic solvent. In this method, dimethylamine is mixed with hexamethylphosphoric triamide, phosphorus oxychloride is gradually added to the mixture. As a result, about 95% of phosphorus oxychloride is converted to hexamethylphosphoric triamide. The reaction is carried out mainly at 0-40 ° C, preferably at a temperature of about 20 ° C. Dimethylamine, which has a low boiling point at atmospheric pressure (7.4 ° C), is returned to the reaction system using a reflux condenser or by carrying out the reaction at elevated pressure. The wet precipitate of dimethylamine hydrochloride after filtration or centrifugation contains a large amount of hexamethylphosphoric triamide. It is dissolved in water, alkalinized, and the released dimethylamine is distilled off. In an aqueous solution contains 10-20% wt. hexamethylphosphoric triamide, 10-20% wt. inorganic salt, a small amount of dimethylamine and organic reaction by-products. Hexamethylphosphoric triamide can be isolated from an aqueous solution by extraction with ether, followed by distillation. The wet cake can also be washed with dimethylamine. The synthesis method is a closed or semi-closed process (see US patent No. 39911110, 11/09/1976).

The advantages of this method are synthesis at temperatures close to room temperature and a high yield of the product. Moreover, a significant drawback is that only 4% of hexamethylphosphoric triamide can be obtained in pure form, the rest is contained in an aqueous solution, where inorganic salts, dimethylamine and organic reaction by-products are present. The separation of absolute hexamethylphosphoric triamide from such a mixture is a complex, multi-stage process and eliminates the benefits of using hexamethylphosphoric triamide as a solvent.

Closest to the technical nature of the claimed invention is a method for producing hexamethylphosphoric triamide, which consists in processing phosphorus oxychloride POCl ₃ in toluene with excess dimethylamine. Dry dimethylamine is cooled to -60 ° C and gradually introduced into toluene. Then, a mixture of POCl ₃ and toluene was added dropwise over three hours with stirring. After precipitation of the dimethylamine salt NH (CH ₃ ) ₂ · HCl, the temperature is raised to room temperature and then to 100 ° C. The salt is filtered off on a Buchner funnel, and toluene is distilled off from the filtrate under vacuum on a water-jet pump. The remaining oil is purified by heating with NaOH, then the mixture is extracted with chloroform, the chloroform layer is separated and hexamethylphosphoric triamide is distilled at 120 ° C (11 mmHg). The yield of hexamethylphosphoric triamide is 60% (see M. Pianka, BD Owen, J. Appl. Chem., London, 5, 525 (1955)).

The disadvantage of this method is that to carry out the main process, it is necessary to maintain a temperature of -60 ° C for three hours, which requires additional energy costs. In addition, the product yield is only 60%.

Also known are methods where diisopropyl, dibutyl ether or chloroform is used as the main reaction medium (see Taitiro Fujinaga, Kosuke Izutsu, Hexamethylphosphoramide: purification and tests for purity // International Union of pure and applied chemistry. - London. - 115- 124).

The technical result of the invention consists in increasing the yield of the pure target reaction product up to 84 - 87% and reducing the energy consumption of production.

The technical result is achieved by the fact that in the method for producing hexamethylphosphoric triamide, which involves treating phosphorus oxychloride with excess dimethylamine in toluene, adding a mixture of phosphorus oxychloride and toluene dropwise, after precipitation of the dimethylamine hydrochloride salt, the reaction temperature is raised to room temperature and then to 100 ° C, filtering salts on a Buchner funnel, distillation of toluene from the filtrate in vacuo, isolation of hexamethylphosphoric triamide by distillation at a pressure of 1.0-1.5 mm Hg, according to the invention The phosphorus oxychloride is treated with excess dimethylamine in toluene in the presence of a catalyst - anhydrous aluminum chloride at a temperature of -5 ... + 5 ° C.

A method for producing hexamethylphosphoric triamide of the formula

with the improvement of production technology.

Hexamethylphosphoric triamide is a highly polar aprotic organic solvent, characterized by a high solvating ability with respect to inorganic cations and many metal complexes.

Distinctive features of the proposed method for producing hexamethylphosphoric triamide are: the use of a higher temperature in the process of the main reaction -5 ... + 5 ° C, which reduces energy costs for cooling the reaction mixture; the use of anhydrous aluminum chloride as a catalyst, which increases the yield of the target reaction product to 84-87%.

The mechanism of action of the catalyst, anhydrous aluminum chloride, is probably similar to the Friedel-Crafts catalytic alkylation mechanism. Dimethylamine can act as a nucleophile in this reaction. Aluminum chloride (Lewis acid) enhances the electrophilicity of phosphorus oxychloride. Perhaps the reaction proceeds according to the following mechanism:

It is known that the presence of amines in the substrate makes the Friedel-Crafts reaction difficult, since amines have a relatively high basicity and are coordinated with Lewis acids, which removes the catalyst from the system. In the case of the reaction of phosphorus oxychloride with dimethylamine, dimethylamine is introduced last into the system, and its addition occurs slowly and gradually. Thus, the released catalyst — anhydrous aluminum chloride — interacts with phosphorus oxychloride.

Experimental studies found that carrying out the main reaction at temperatures of -60 ... -6 ° C gives the yield of the target reaction product only 60-75%, that is, it requires high energy consumption and provides a lower yield of hexamethylphosphoric triamide, and the implementation of the method of producing hexamethylphosphoric triamide ... + 10 ° C is complicated by the volatility of dimethylamine, which leads to a decrease in the yield of the target reaction product.

Experimental studies have shown that increasing the temperature of the main reaction to -5 ... + 5 ° C in the presence of a catalyst — anhydrous aluminum chloride — makes it possible to increase the yield of the pure target product of the reaction to 84-87% and reduce the energy consumption of production.

The proposed method for producing hexamethylphosphoric triamide is illustrated by drawings, in which Fig. 1 shows a diagram of an apparatus for conducting the main reaction for the synthesis of hexamethylphosphoric triamide, and Fig. 2 is a diagram of a vacuum distillation apparatus.

The apparatus for carrying out the main synthesis reaction of hexamethylphosphoric triamide (see FIG. 1) includes a three-necked flask 1, which is placed in a heat exchanger or cryostat 2. A drive stirrer 3 is installed in the neck of a three-necked flask 1. A dropping funnel 4 is installed in the side neck of a three-necked flask 1. In another the neck of the three-necked flask 1 is equipped with a reflux condenser 5, which is equipped with a calcium chloride tube.

The installation scheme for vacuum distillation (see figure 2) includes a flask 6 for vacuum distillation, in the neck of which is installed a capillary 7 for air intake. A thermometer 8 is installed in the lateral neck of the vacuum distillation flask 6. The vacuum distillation flask 6 itself is placed in an air bath 9, under which the heating element 10 is located. The vacuum in the installation for vacuum distillation is created by a vacuum pump 11, the pressure in the system is controlled by a pressure gauge 12. Through a direct refrigerator 13, the flask 6 for vacuum distillation is connected to the allonge spider 14 having receiving flasks 15.

The method of obtaining hexamethylphosphoric triamide is as follows. In a three-necked flask 1 with a capacity of 1500 cm ³ (see Fig. 1), 900 cm of absolute toluene are charged, after which the three-necked flask 1 is cooled to a temperature

-5 ... + 5 ° С. To maintain the desired temperature, a heat exchanger or cryostat 2 is used. Next, 250 cm of absolute dimethylamine are added to a three-necked flask 1 and a catalyst is added - 0.2 g of anhydrous aluminum chloride (AlCl ₃ ). 66 g of phosphorus oxychloride POCl ₃ dissolved in 100 cm ^{3 of} toluene are added dropwise through a dropping funnel 4 to the resulting mixture over 4 hours with constant stirring using a drive stirrer 3. As added, a precipitate of dimethylamine hydrochloride is formed. The reaction temperature was brought to room temperature and left to stand for 6-7 hours. After that, the temperature was raised to 100 ° C, heating was continued for 2 hours, while the vapors were trapped in a reflux condenser 5 equipped with a calcium chloride tube, and the condensate was returned to the reaction mixture in a three-necked flask 1.

The resulting precipitate of dimethylamine salt NH (CH ₃ ) ₂ · HCl is separated through a Buchner funnel (not shown). Toluene is distilled off under vacuum of a water-jet pump (not shown). The remaining hexamethylphosphoric triamide is distilled off under vacuum of 1.0-1.5 mm Hg. The distillation installation diagram is shown in Figure 2. The mixture is placed in a vacuum distillation flask 6 equipped with a capillary 7 for air intake and a thermometer 8. The vacuum distillation flask 6 is heated to a temperature of 69-77 ° C in an air bath 9 using a heating element 10 The vacuum is created by a vacuum pump 11 and fixed with a pressure gauge 12. The pairs of hexamethylphosphoric amide are condensed in a direct refrigerator 13, and the condensate flows from sponge 14 to the receiving flasks 15.

Examples confirming the claimed method for producing hexamethylphosphoric triamide

Example 1. In a three-necked flask 1 with a capacity of 1500 cm ³ load 900 cm ³ absolute toluene. Then the flask 1 is cooled to a temperature of 0 ° C in the heat exchanger 2, then add 250 cm ^{3 of} absolute dimethylamine and add the catalyst - 0.2 g of anhydrous aluminum chloride (AlCl ₃ ). 66 g of phosphorus oxychloride dissolved in 100 cm of toluene are added dropwise to the resulting mixture over 4 hours. As added, a precipitate of dimethylamine hydrochloride is formed. The reaction temperature was brought to room temperature and left to stand for 6 hours. After that, the temperature is raised to 100 ° C. The mixture is heated for 2 hours, then the precipitate is separated through a Buchner funnel (not shown). Toluene is distilled off under vacuum of a water-jet pump (not shown). The remaining hexamethylphosphoric triamide is distilled under vacuum at 1.0 mm Hg.

The distilled product is a colorless liquid, so Kip. 232-234 ° C / 760 mmHg or 70-76 ° C / 1.0-1.5 mm Hg; η _D ²⁰ = 1.4572; Belstein's chloride test is negative. The mass of the obtained hexamethylphosphoric triamide 67 g. Product yield 87%.

Calculated,%: C 40.21; H 10.12; N, 23.45; P 17.28. C ₆ H ₁₈ N ₃ OP

Found,%: C 40.45; H 10.17; N, 23.28; P 17.00.

The position of the peaks of the absorption spectrum, cm ^-1 : 1430-1470 C-n 1150-1350 P = o 700-730 P-n

Example 2. In a three-necked flask 1 with a capacity of 1500 cm ³ load 900 cm ^{3 of} absolute toluene, cooled to a temperature of -5 ° C in a heat exchanger 2, add 250 cm ^{3 of} absolute dimethylamine and add a catalyst - 0.2 g of anhydrous aluminum chloride (AlCl ₃ ) . 66 g of phosphorus oxychloride dissolved in 100 cm ^{3 of} toluene are added dropwise to the mixture over 4 hours. As added, a precipitate of dimethylamine hydrochloride is formed. The reaction temperature was brought to room temperature and left to stand for 6 hours. After that, the temperature is raised to 100 ° C. Heating is continued for 2 hours, then the precipitate is separated through a Buchner funnel (not shown). Toluene is distilled off under vacuum of a water-jet pump (not shown). The remaining hexamethylphosphoric triamide is distilled under vacuum at 1.0 mm Hg.

The distilled product is a colorless liquid, so Kip. 232-234 ° C / 760 mmHg or 70-76 ° C / 1.0-1.5 mm Hg; η _D ²⁰ = 1.4572; Belstein's chloride test is negative. The mass of the obtained hexamethylphosphoric triamide 65.5 g. Product yield 85%.

Calculated,%: C 40.21; H 10.12; N, 23.45; P 17.28. C ₆ H ₁₈ N ₃ OP

Found,%: C 40.45; H 10.17; N, 23.28; P 17.00.

The position of the peaks of the absorption spectrum, cm ^-1 : 1430-1470 C-n 1150-1350 P = o 700-730 P-n

Example 3. In a three-necked flask 1 with a capacity of 1500 cm ^3, 900 cm ^{3 of} absolute toluene was charged, cooled to a temperature of + 5 ° C in heat exchanger 2, 250 cm of absolute dimethylamine were added, and 0.2 g of anhydrous aluminum chloride (AlCl ₃ ) catalyst was added. 66 g of phosphorus oxychloride dissolved in 100 cm ^{3 of} toluene are added dropwise to the mixture over 4 hours. As added, a precipitate of dimethylamine hydrochloride is formed. The reaction temperature was brought to room temperature and left to stand for 7 hours. After that, the temperature is raised to 100 ° C. Heated for 2 hours, then the precipitate is separated through a Buchner funnel (not shown). Toluene is distilled off under vacuum of a water-jet pump (not shown). The remaining hexamethylphosphoric triamide is distilled under vacuum of 1.5 mm Hg. pillar.

The distilled product is a colorless liquid, so Kip. 232-234 ° C / 760 mmHg or 70-76 ° C / 1.0-1.5 mm Hg; η _D ²⁰ = 1.4572; Belstein's chloride test is negative. The mass of hexamethylphosphoric triamide obtained was 64.7 g. Product yield 84%.

Calculated,%: C 40.21; H 10.12; N, 23.45; P 17.28. C ₆ H ₁₈ N ₃ OP

Found,%: C 40.45; H 10.17; N, 23.28; P 17.00.

The position of the peaks of the absorption spectrum, cm ^-1 : 1430-1470 C-n 1150-1350 P = o 700-730 P-n

As can be seen from the examples, the claimed invention allows to obtain the reaction product - hexamethylphosphoric triamide, which is a colorless liquid, characterized by a boiling point of 232-234 ° C at a pressure of 760 mm Hg or 70-76 ° C at 1.0-1.5 mm Hg and optical density at 20 ° C η _D ²⁰ = 1.4572, Belstein's chloride test is negative. The elemental composition of the obtained product corresponds to the elemental composition of hexamethylphosphoric triamide. The position of the peaks of the absorption spectrum confirms the presence of characteristic atomic groups of hexamethylphosphoric triamide.

The claimed invention in comparison with the prototype (see M. Pianka, B.D. Owen, J.Appl. Chem., London, 5, 525 (1955)) allows:

- to carry out the main reaction at higher temperatures, which reduces the energy consumption of production and simplifies the hardware design;

- increase the yield of the target reaction product - hexamethylphosphoric triamide to 84-87%.

Claims (1)

A method for producing hexamethylphosphoric triamide, which involves treating phosphorus oxychloride with an excess of dimethylamine in toluene, adding a dropwise mixture of phosphorus oxychloride and toluene, after precipitating the dimethylamine hydrochloride salt, raising the reaction temperature to room temperature and then to 100 °, filtering the salt on a Buchner funnel, distillation filtrate under vacuum, the allocation of hexamethylphosphoric triamide by distillation at a pressure of 1.0-1.5 mm RT.article, characterized in that the treatment of phosphorus oxychloride with excess dimethylamine in the environment of toluene is carried out in the presence of a catalyst - anhydrous aluminum chloride at a temperature of -5 ... + 5 ° C.

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