A polynitroaminopyrazole energetic compound and its preparation method and application

Abstract

The present invention discloses a polynitroaminopyrazole energetic compound, a preparation method and application thereof. The compound comprises the following molecular structural formula: the synthesis method comprises the following steps: first, 3,5-dinitro-4-chloropyrazole is reacted with bromoacetone to obtain an intermediate 1-acetonyl-3,5-dinitro-4-chloropyrazole; then, the intermediate is nitrated to obtain an energetic compound N-trinitromethyl-3,5-dinitro-4-chloropyrazole; and finally, chlorine atoms are substituted with amino groups to prepare a target compound N-trinitromethyl-4-amino-3,5-dinitropyrazole (PNAP). The energetic compound PNAP has high oxygen content, high energy density and good safety performance, and can be used as a high-energy oxidant in the fields of propellants and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of energetic material synthesis, and in particular relates to a polynitroaminopyrazole energetic compound and a preparation method and application thereof. Background Art

[0002] Energetic materials are primarily categorized by their intended use into three types: explosives, propellants, and pyrotechnics. As energy carriers for conventional firepower weapons, the performance of energetic materials determines the weapon's state-of-the-art capabilities. To enhance weapon combat effectiveness, improving the energy level of energetic materials is a perennial development theme in the field. The development of energetic materials has primarily progressed through the development of materials such as 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-azacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), and hexanitrohexaazaisowurtzitane (CL-20). While their energy levels have steadily increased, their safety performance has also gradually declined.

[0003] The introduction of amino groups can form intramolecular and intermolecular hydrogen bonds, which is an effective method to improve the safety of energetic materials. Such compounds synthesized based on this idea include 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 2,6-diamino-3,5-dinitropyrazole-1-oxide (LLM-105), 1,1-diamino-2,2-dinitroethylene (FOX-7), and 4-amino-3,5-dinitropyrazole (LLM-116).

[0004] LLM-116 has high energy and very low sensitivity, with a density of 1.900 g·cm -3 , the energy is 90% of HMX, and it is a high-energy insensitive material with great application prospects.

[0005] The trinitromethyl group is an explosive group with high energy density and high oxygen content. Introducing it into the LLM-116 structure can further improve its oxygen balance and energy density. The common method is to introduce an acetone group into the pyrazole ring, and then further nitrate it to introduce the trinitromethyl group.

[0006] The research group of Lin Xiangyang from Nanjing University of Science and Technology used LLM-116 to react with bromoacetone, attached the acetone group and then nitrated it. At the same time as the trinitromethyl group was introduced, the amino group was converted into nitramine (the reaction process is as follows Figure 1 The obtained compound has poor stability and is only used as a reaction intermediate. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem of nitration of amino groups to nitramines in the prior art, and to provide a polynitroaminopyrazole energetic compound, a preparation method, and applications thereof. The energetic compound has high oxygen content, high energy density, and moderate sensitivity, and can be used as a high-energy oxidant in fields such as solid propellants. The preparation method of the present invention adopts an innovative approach of nitration followed by amination, successfully preparing the target compound. The synthetic route is efficient and safe, and has potential for industrial application.

[0008] The technical route of the preparation method of the present invention is as follows: LLM-116 has the advantages of high energy and low sensitivity. Connecting it to a trinitromethyl group through a CN bond can further improve the oxygen content and energy performance of the molecule. Therefore, a trinitromethyl group is introduced into the structure of LLM-116 to design a molecule N-trinitromethyl-4-amino-3,5-dinitropyrazole. Specifically, starting from 3,5-dinitro-4-chloropyrazole as a raw material, 3,5-dinitro-4-chloropyrazole is first reacted with bromoacetone to obtain an intermediate 1-acetonyl-3,5-dinitro-4-chloropyrazole, which is then nitrated to obtain an intermediate energetic compound N-trinitromethyl-3,5-dinitro-4-chloropyrazole. Finally, the target compound N-trinitromethyl-4-amino-3,5-dinitropyrazole is prepared by replacing the chlorine atom with an amino group.

[0009] The technical solution of the present invention is to first provide a polynitroaminopyrazole energetic compound having the following molecular structure:

[0010]

[0011] Furthermore, the oxygen balance of the polynitroaminopyrazole energetic compound is as high as 5%, and the density reaches 1.91 g·cm -1 , the decomposition temperature reaches 122℃, the impact sensitivity reaches 9J, and the friction sensitivity reaches 120N.

[0012] The present invention also provides a method for preparing the above-mentioned polynitroaminopyrazole energetic compound, comprising the following steps:

[0013] S1, 3,5-dinitro-4-chloropyrazole reacts with bromoacetone to obtain 1-acetonyl-3,5-dinitro-4-chloropyrazole;

[0014] S2, 1-acetonyl-3,5-dinitro-4-chloropyrazole is acidified with a mixture of nitric acid and sulfuric acid to obtain a polynitropyrazole energetic compound: N-trinitromethyl-3,5-dinitro-4-chloropyrazole;

[0015] S3. N-trinitromethyl-3,5-dinitro-4-chloropyrazole is subjected to amination to obtain a polynitroaminopyrazole energetic compound: N-trinitromethyl-4-amino-3,5-dinitropyrazole. Furthermore, in step S1 above, 3,5-dinitro-4-chloropyrazole and bromoacetone are reacted at room temperature for 20 to 30 hours using water and acetone as the reaction solvents. The resulting reaction solution is filtered to obtain 1-acetonyl-3,5-dinitro-4-chloropyrazole.

[0016] Furthermore, in the above step S1, the molar ratio of bromoacetone to 3,5-dinitro-4-chloropyrazole is (1:1) to (1.5:1).

[0017] Furthermore, in the above step S2: the mixture of nitric acid and sulfuric acid refers to 100% mass concentration of sulfuric acid and 100% mass concentration of nitric acid mixed in a volume ratio of (1:1) to (10:1); the reaction temperature is room temperature; the reaction time is 20-48h; after the reaction, the reactant is poured into an ice-water mixture to precipitate a white solid product, which is filtered, washed with water, and dried to obtain a white solid product N-trinitromethyl-3,5-dinitro-4-chloropyrazole.

[0018] Furthermore, in the above step S3, the aminating agent is ammonia water or ammonia gas.

[0019] Furthermore, in the above step S3, when the amination reagent is aqueous ammonia: the reaction solvent is one of a water / ethyl acetate combination, a water / dichloroethane combination, and a water / dichloromethane combination; the volume ratio of water to the organic solvent in the reaction solvent is (1:5) to (1:1); the molar ratio of the reaction substrate to aqueous ammonia is (1:20) to (1:1); the amination temperature is room temperature, and the amination time is 10 to 24 hours; stirring is performed during the amination process at a stirring speed of 50 to 300 rpm, and the reaction system is in a two-phase state; after the amination reaction, the obtained reaction solution is subjected to reduced pressure rotary evaporation to remove the organic solvent, and after suction filtration, washing with water, and drying, the target product N-trinitromethyl-4-amino-3,5-dinitropyrazole is obtained as a yellow solid.

[0020] Furthermore, in the above step S3, when the amination reagent is ammonia: the reaction solvent is an aprotic solvent, and the non-ionic solvent includes one or more of acetone, acetonitrile, ethyl acetate, ether, dichloroethane or dichloromethane; the amination reaction temperature is room temperature, and the reaction time is 3 to 10 hours; the molar ratio of the reaction substrate to ammonia is (1:2) to (1:1); after the amination reaction, the obtained reaction solution is subjected to reduced pressure rotary evaporation to remove the organic solvent, and water is added to soak the solid. After suction filtration, washing with water, and drying, the yellow solid target product N-trinitromethyl-4-amino-3,5-dinitropyrazole is obtained.

[0021] The synthetic route is as follows:

[0022]

[0023] The synthetic route for the above reaction process is as follows: 3,5-dinitro-4-chloropyrazole (substrate 1) reacts with bromoacetone to prepare 1-acetonyl-3,5-dinitro-4-chloropyrazole (intermediate 2), intermediate 2 is nitrated using a nitric acid-sulfuric acid mixture to prepare N-trinitromethyl-3,5-dinitro-4-chloropyrazole (intermediate 3), and intermediate 3 is aminated using ammonia water or ammonia gas to obtain the target molecule N-trinitromethyl-4-amino-3,5-dinitropyrazole (PNAP). The specific steps are as follows:

[0024] (1) Preparation of intermediate 2: The reaction raw materials are substrate 1 and bromoacetone, the reaction reagents are water and acetone, the reaction time is 20 to 30 hours, and the reaction temperature is room temperature. After the reaction is completed, the acetone is removed by vacuum rotary evaporation, and the intermediate is filtered, washed with water, dried, and recrystallized with methanol to obtain the intermediate 1-acetonyl-3,5-dinitro-4-chloropyrazole (intermediate 2);

[0025] (2) Preparation of Intermediate 3: Intermediate 2 was nitrated using a mixture of nitric and sulfuric acid, which was prepared from 100% sulfuric acid and 100% nitric acid. The reaction temperature was room temperature and the reaction time was 20-48 h. After the reaction was completed, the reaction solution was poured into an ice-water mixture to precipitate a white solid product. After filtration, washing with water, and drying, a white solid product, N-trinitromethyl-3,5-dinitro-4-chloropyrazole (Intermediate 3), was obtained.

[0026] (3) Preparation of target molecule: The amination reagent is ammonia water or ammonia gas, the reaction temperature is room temperature, and an aprotic organic solvent such as ethyl acetate, acetonitrile, acetone, dichloroethane, dichloromethane, or a mixed solvent of water and organic solvent (such as water / ethyl acetate, water / dichloroethane, water / dichloromethane, etc.) is used as the reaction solvent. N-trinitromethyl-3,5-dinitro-4-chloropyrazole is ammoniated at room temperature for a certain time. The resulting reaction solution is subjected to reduced pressure rotary evaporation to remove the organic solvent, and water is added to dissolve impurities. After filtration, washing with water, and drying, the target product N-trinitromethyl-4-amino-3,5-dinitropyrazole (PNAP) is obtained as a yellow solid.

[0027] The method is simple to synthesize, has a moderate yield, low cost, and is suitable for engineering scale-up. The designed target molecule, N-trinitromethyl-4-amino-3,5-dinitropyrazole, has an oxygen balance of 5% and a density of 1.91 g.cm -1 , decomposition temperature 122 ℃, impact sensitivity 9J, friction sensitivity 120N, with high oxygen balance, high energy density and good safety performance, it has the potential to be used as an oxidizer in solid propellants.

[0028] Therefore, the present invention also provides the use of the polynitroaminopyrazole energetic compound as an oxidant in the preparation of solid propellants.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The polynitroaminopyrazole energetic compound of the present invention has an oxygen balance of 5% and a density of 1.91 g·cm -1 , decomposition temperature 122 ℃, impact sensitivity 9J, friction sensitivity 120N, with high oxygen balance, high energy density and good safety performance, which is of great significance to improving the energy level of solid propellant.

[0031] (2) The polynitroaminopyrazole energetic compound of the present invention introduces a trinitromethyl group into the pyrazole ring structure, which brings high energy density and high oxygen content but also causes the problem of reduced safety performance of the compound; at the same time, the amino group is introduced into the pyrazole ring by amination, which can form intramolecular and intermolecular hydrogen bonds, thereby improving the stability and safety performance of the compound.

[0032] (3) In the synthesis method of the present invention, 3,5-dinitro-4-chloropyrazole is used as the raw material, and the target compound N-trinitromethyl-4-amino-3,5-dinitropyrazole is prepared through reactions such as acetonyl substitution, nitration, and amination. This method is simple to synthesize, has a moderate yield, and is low in cost, making it suitable for engineering scale-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A synthetic route for polynitro-substituted nitraminopyrazole compounds in the prior art;

[0034] Figure 2 1 is a synthetic route of N-trinitromethyl-4-amino-3,5-dinitropyrazole according to an embodiment of the present invention;

[0035] Figure 3 : is the hydrogen spectrum of N-trinitromethyl-4-amino-3,5-dinitropyrazole obtained in the examples of the present invention;

[0036] Figure 4 This is the carbon spectrum of N-trinitromethyl-4-amino-3,5-dinitropyrazole in the examples of the present invention. DETAILED DESCRIPTION

[0037] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0038] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0039] Example 1:

[0040] A method for preparing a polynitroaminopyrazole energetic compound:

[0041] Step (1) 0.963 g (5 mmol) of 3,5-dinitro-4-chloropyrazole (1), 0.504 g (6 mmol) of NaHCO3 and 7 mL of water were added to a 100 mL round-bottom flask and stirred at room temperature to dissolve. 0.42 mL of bromoacetone and 12 mL of acetone were mixed and added dropwise to the round-bottom flask. After the addition was complete, stirring was continued for 24 hours. After the reaction was completed, acetone was removed by vacuum rotary evaporation, and the mixture was filtered, washed with water, dried, and recrystallized with methanol to obtain 0.895 g of off-white solid 1-acetonyl-3,5-dinitro-4-chloropyrazole (intermediate 2) with a yield of 72%. 1 H NMR (500MHz, DCCl3, 25℃): δ=5.49(s), 2.30(s)ppm; 13 C NMR (125MHz, DCCl3, 25℃): δ=195.49, 148.41, 141.53, 106.57, 63.24, 25.95ppm.

[0042] Step (2) 5 mL of 100% nitric acid was slowly added dropwise to 6 mL of 100% sulfuric acid under an ice bath, and then 0.497 g (2 mmol) of 1-acetonyl-3,5-dinitro-4-chloropyrazole (Intermediate 2) was added in batches to the prepared mixed acid. After the addition was completed, the ice bath was removed and the reaction was carried out at room temperature for 48 hours. The reaction solution was poured into an ice-water mixture under vigorous stirring to precipitate a white solid product. After filtration, washing with water, and drying, 0.458 g of a white solid product, N-trinitromethyl-3,5-dinitro-4-chloropyrazole (Intermediate 3), was obtained with a yield of 67% and a melting point of 62°C. 13 C NMR (125MHz, DCCl3, 25°C): δ=151.66, 141.90, 118.06, 111.97ppm.

[0043] Step (3) The amination reagent is aqueous ammonia. 5 mL of water, 8 mL of ethyl acetate, and 0.342 g (1 mmol) of N-trinitromethyl-3,5-dinitro-4-chloropyrazole (Intermediate 3) are added to a 100 mL round-bottom flask and stirred at room temperature to dissolve. The stirring speed is controlled at 200 rpm to make the system a two-phase state. 0.5 mL of 25% aqueous ammonia is added dropwise. After the addition is complete, the stirring reaction is continued for 24 hours. The resulting reaction solution is subjected to reduced pressure rotary evaporation to remove the organic solvent. Water is added to dissolve impurities. After filtration, washing, and drying, 0.135 g of the target product N-trinitromethyl-4-amino-3,5-dinitropyrazole (PNAP) as a yellow solid is obtained in a yield of 42%.

[0044] In step (3), the aminating reagent was ammonia. 10 mL of acetonitrile and 0.342 g (1 mmol) of N-trinitromethyl-3,5-dinitro-4-chloropyrazole (intermediate 3) were added to a 100 mL round-bottom flask and stirred at room temperature to dissolve. After 2 equivalents of ammonia were introduced, the mixture was stirred and reacted for 5 h. The resulting reaction solution was subjected to vacuum rotary evaporation to remove the organic solvent. Water was added to dissolve impurities. After filtration, washing with water, and drying, 0.151 g of the target product N-trinitromethyl-4-amino-3,5-dinitropyrazole (PNAP) was obtained as a yellow solid in a yield of 47%.

[0045] The decomposition temperature of the obtained product PNAP is 122℃, and the hydrogen and carbon spectra are as follows: Figure 3 and Figure 4 As shown, it can be seen that: 1 HNMR (500MHz, DMSO-d6, 25℃): δ=8.63(s)ppm; 13 C NMR (125 MHz, DMSO-d6, 25°C): δ = 149.03, 133.21, 129.04, 121.22 ppm, indicating that the structure of the obtained product was consistent with the molecular structure of N-trinitromethyl-4-amino-3,5-dinitropyrazole.

[0046] In the amination reaction step (3) of preparing PNAP, when the amination reagent is aqueous ammonia, the reaction stirring speed is too fast or the amount of aqueous ammonia is too high, resulting in a complex khaki solid mixture. When the amination reagent is ammonia gas, the amount of ammonia gas introduced is too high, resulting in a khaki solid mixture. The specific reason is that when the amount and concentration of ammonia are too high, the C-NO2 on the pyrazole ring is replaced by an amino group, and the trinitromethyl group is also hydrolyzed by alkaline hydrolysis.

[0047] The prepared target molecule, PNAP, was vacuum-dried at 50°C for 2 hours and then subjected to impact and friction sensitivity tests. The test data are shown in Table 1. As shown in Table 1, the oxygen balance coefficients of commonly used energetic materials, such as RDX, HMX, and CL-20, are negative, while PNAP has an oxygen balance coefficient of 5.0% and exhibits good mechanical sensitivity.

[0048] Table 1 Molecular oxygen content and sensitivity data of target molecules and other common energetic materials

[0049]

[0050] [a] Oxygen balance coefficient [%]; [b] Impact sensitivity [J]; [c] Friction sensitivity [N].

[0051] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

[0052] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for preparing a polynitroaminopyrazole energetic compound, characterized in that: The polynitroaminopyrazole energetic compound has the molecular structural formula shown below: ； Its oxygen balance is up to 5%, and its density reaches 1.91 g·cm -1 , the decomposition temperature reaches 122℃, the impact sensitivity reaches 9 J, and the friction sensitivity reaches 120N; The preparation method comprises the following steps: S1, 3,5-dinitro-4-chloropyrazole reacts with bromoacetone to obtain 1-acetonyl-3,5-dinitro-4-chloropyrazole; S2, 1-acetonyl-3,5-dinitro-4-chloropyrazole is acidified with a mixture of nitric acid and sulfuric acid to obtain a polynitropyrazole energetic compound: N-trinitromethyl-3, 5-dinitro-4-chloropyrazole; S3, N-trinitromethyl-3,5-dinitro-4-chloropyrazole is subjected to amination to obtain a polynitroaminopyrazole energetic compound: N-trinitromethyl-4-amino-3, 5-dinitropyrazole; In the step S3, The ammoniating agent is ammonia water or ammonia gas; When the amination reagent is aqueous ammonia: the reaction solvent is one of a water / ethyl acetate combination, a water / dichloroethane combination, or a water / dichloromethane combination; the volume ratio of water to the organic solvent in the reaction solvent is (1:5) to (1:1); the molar ratio of the reaction substrate to aqueous ammonia is (1:20) to (1:1); the amination temperature is room temperature, and the amination time is 10 to 24 hours; stirring is performed during the amination process at a stirring speed of 50 to 300 rpm, and the reaction system is in a two-phase state; after the amination reaction, the resulting reaction solution is subjected to reduced pressure rotary evaporation to remove the organic solvent, and the target product N-trinitromethyl-4-amino-3,5-dinitropyrazole is obtained after suction filtration, water washing, and drying. When the amination reagent is ammonia: the reaction solvent is an aprotic solvent, and the aprotic solvent is one or more of acetone, acetonitrile, ethyl acetate, ether, dichloroethane, or dichloromethane; the amination reaction temperature is room temperature, and the reaction time is 3 to 10 hours; the molar ratio of the reaction substrate to ammonia is (1:2) to (1:1); after the amination reaction, the obtained reaction solution is subjected to reduced pressure rotary evaporation to remove the organic solvent, and water is added to soak the solid. After suction filtration, washing with water, and drying, the yellow solid target product N-trinitromethyl-4-amino-3,5-dinitropyrazole is obtained.

2. The method for preparing the polynitroaminopyrazole energetic compound according to claim 1, wherein: In the step S1, water and acetone are used as reaction solvents, 3,5-dinitro-4-chloropyrazole and bromoacetone are reacted at room temperature for 20 to 30 hours, and the resulting reaction solution is filtered to obtain 1-acetonyl-3,5-dinitro-4-chloropyrazole.

3. The method for preparing the polynitroaminopyrazole energetic compound according to claim 1, wherein: In step S1, the molar ratio of bromoacetone to 3,5-dinitro-4-chloropyrazole is (1:1) to (1.5:1).

4. The method for preparing the polynitroaminopyrazole energetic compound according to claim 1, wherein: In the step S2: A mixture of nitric acid and sulfuric acid refers to a mixture of 100% mass concentration of sulfuric acid and 100% mass concentration of nitric acid in a volume ratio of (1:1) to (10:1); The reaction temperature is room temperature; the reaction time is 20-48h; After the reaction, the reactant was poured into an ice-water mixture to precipitate a white solid product, which was filtered, washed with water, and dried to obtain a white solid product, N-trinitromethyl-3,5-dinitro-4-chloropyrazole.

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