High energy nitroform-based compounds with improved 4-amino-3,5-dinitro-pyrazole oxygen balance and methods of synthesis thereof

Abstract

This invention discloses a high-energy nitroform compound that improves the oxygen balance of 4-amino-3,5-dinitropyrazole and its synthesis method. First, 1-acetone-LLM-116 is synthesized by reacting LLM-116 ammonium salt with chloroacetone and potassium bromide. Then, the acetone group is nitrated in one step to obtain 1-nitroform-LLM-116, with the molecular formula C4H2N8O. 10 Its density is 1.866 g∙cm³. ‑3 The carbon dioxide-oxygen balance is +4.97%, and the oxygen content is 49.67%. The theoretical detonation velocity is approximately 10% higher than that of LLM-116, making it suitable as a high-energy material for applications such as oxidizers in explosives or solid propellants. This invention offers advantages such as simple synthesis, high yield, and low cost, increasing the oxygen balance of LLM-116 from -32.37% to +4.97%.

Description

Technical Field

[0001] This invention relates to a high-energy nitroform compound that improves the oxygen balance of 4-amino-3,5-dinitropyrazole and its preparation method, belonging to the field of energetic materials technology. Background Technology

[0002] The density of 4-amino-3,5-dinitropyrazole (LLM-116) is 1.9 g·cm³. -3 Its energy is 90% of that of cyclotetramethylenetetranitramine (HMX), H 50 It measures 167.5 cm and has a detonation velocity of 8.24 km / s. -1 The explosion pressure is 29.42 GPa. LLM-116 was designed by Lawrence Livermore National Laboratory in the United States in 1993. Nearly ten years later, the laboratory synthesized LLM-116 via the VNS reaction. In 2007, Wang Yinglei et al. of the Xi'an Institute of Modern Chemistry studied the mechanism and influencing factors of the VNS reaction and optimized the best reaction conditions (Journal of Explosives and Pyrotechnics, 2007, 30: 20-23). ​​In 2010, Hervé et al. synthesized LLM-116 by ammoniation of 3,4,5-trinitropyrazole (Angew. Chem. Int. Ed., 2010, 49: 3177-3181). In 2012, Dalinger et al. synthesized LLM-116 by ammoniation of 4-chloro-3,5-dinitropyrazole (Synthesis, 2012, 44: 2058-2064). LLM-116, as a high-energy, low-sensitivity energetic material, has important application prospects.

[0003] Due to the inductive effect of the nitro group, the hydrogen atom on the pyrazole ring nitrogen in LLM-116 exhibits a certain acidity, allowing it to form various organic amine salts with some basic substances (such as guanidine, triaminoguanidine, and amidourea); and to form complexes with metal ions (such as potassium, lead, and copper). In 2009, Wang Bozhou et al. from the Xi'an Institute of Modern Technology synthesized 1-picryl-4-amino-3,5-dinitropyrazole and 2,4,6-tris(4-amino-3,5-dinitropyrazole-1-yl)-1,3,5-triazine using LLM-116 as a raw material through a condensation reaction with 2,4,6-trinitrochlorobenzene and trichloromelamine (Energetic Materials, 2009, 17: 293-295). Furthermore, various forms of bridging bis-LLM-116 compounds have been synthesized. However, these compounds generally exhibit poor oxygen balance, resulting in performance slightly lower than that of LLM-116. To improve the energy performance of LLM-116 derivatives, their oxygen balance must be improved. Nitroform has high energy and good oxygen balance, but its sensitivity is relatively high. The patent application No. 202111443058.X reported the introduction of nitroform into trinitropyrazole, with an impact sensitivity of only 3.8J. Too high a sensitivity will greatly affect its application. Summary of the Invention

[0004] The purpose of this invention is to provide a high-energy nitroform compound that can improve the oxygen balance of LLM-116 and its preparation method.

[0005] Technical solution to achieve the purpose of this invention:

[0006] A high-energy nitroform compound with the chemical formula C4H2N8O 10 The structural formula is:

[0007]

[0008] The crystal structure of this high-energy nitroform compound has the following characteristics:

[0009] Crystal system: Monoclinic;

[0010] Point group: P21 / n;

[0011] Unit cell parameters: α=γ=90°, β=98.696(3)°;

[0012] Unit cell volume:

[0013] Z = 8;

[0014] Density: 1.895 g·cm³ -3 (193K).

[0015] The present invention provides a method for preparing a high-energy nitroform compound, comprising:

[0016] (1) The step of reacting compound 1 with chloroacetone and potassium bromide in N,N-dimethylformamide to synthesize compound 2;

[0017]

[0018] (2) The step of preparing the target product by nitrifying compound 2 in the presence of fuming nitric acid and concentrated sulfuric acid and then post-processing;

[0019]

[0020] Preferably, in step (1), the molar ratio of compound 1, potassium bromide, and chloroacetone is 1:1:1.5; the reaction temperature is 60–90 °C; and the reaction time is 0.5–3 h.

[0021] Preferably, in step (2), the volume ratio of fuming nitric acid to concentrated sulfuric acid is 1 to 1.5:1; the amount ratio of fuming nitric acid to compound 2 is 8 to 10 mL: 1 g; and the reaction temperature is room temperature.

[0022] Preferably, in step (2), compound 2 is added in batches to concentrated sulfuric acid at 15-20°C, and fuming nitric acid is added dropwise at -5-5°C. After the addition is complete, the mixture is stirred at this temperature for 1 hour, and the reaction system is gradually restored to room temperature over 2-3 hours. Then, the reaction is stirred at this temperature for 4-8 hours.

[0023] Preferably, in step (2), the post-treatment refers to: after the nitration reaction is completed, the reaction solution is poured into ice water for quenching, filtered, the filter cake is removed, the filtrate is left to stand at room temperature for more than 24 hours, filtered to precipitate the precipitate, and the target product is obtained.

[0024] The above-mentioned high-energy compounds are used as oxidizers in explosives or solid propellants in weapons and aerospace.

[0025] Compared with the prior art, the beneficial effects of this invention are:

[0026] (1) The high-energy compound of the present invention has a covalent structure in which the nitro group is directly connected to LLM-116, and the combination of the high-energy oxygen-rich group and the insensitive parent ring achieves a balance between energy and stability.

[0027] (2) The high-energy compound of the present invention increases the oxygen balance of LLM-116 from -32.37% to +4.97%.

[0028] (3) The density of the high-energy compound of the present invention is 1.866 g·cm³. -3 It exhibits excellent detonation performance, with a calculated detonation pressure of 35.59 GPa and a detonation velocity of 9028 m / s based on EXPLO5. -1 The theoretical detonation velocity is about 10% higher than that of LLM-116.

[0029] (4) In the synthesis method of the high-energy nitroform compound of the present invention, the intermediate LLM-116 ammonium salt for the synthesis of LLM-116 is used as raw material, and 1-nitroform-4-amino-3,5-dinitropyrazole is prepared in two steps. The method is simple to synthesize, has a high yield, and low cost, and is suitable for engineering scale-up. Attached Figure Description

[0030] Figure 1 This is a crystal structure diagram of 1-nitroform-4-amino-3,5-dinitropyrazole of the present invention.

[0031] Figure 2 This is a unit cell packing diagram of 1-nitroform-4-amino-3,5-dinitropyrazole of the present invention.

[0032] Figure 3 The image shows the 1H NMR spectrum of 1-nitroform-4-amino-3,5-dinitropyrazole of this invention (using deuterated acetone as solvent).

[0033] Figure 4The image shows the carbon NMR spectrum of 1-nitroform-4-amino-3,5-dinitropyrazole of this invention (solvent is deuterated acetone).

[0034] Figure 5 The infrared spectrum of 1-nitroform-4-amino-3,5-dinitropyrazole of the present invention is shown.

[0035] Figure 6 This is a thin-layer chromatogram of the product obtained from 1-nitroform-4-amino-3,5-dinitropyrazole and Comparative Example 2. Detailed Implementation

[0036] The following embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0037] This invention introduces nitroform into the insensitive LLM-116 parent ring, which not only increases the energy of the parent ring and improves its oxygen balance, but also reduces the sensitivity of nitroform. The combination of the two can achieve a balance between energy and stability to a certain extent, which is an effective strategy for preparing high-energy, low-sensitivity energetic materials.

[0038] This invention uses commercially available 4-chloropyrazole as a substrate and prepares the raw material LLM-116 ammonium salt (4-amino-3,5-dinitropyrazole ammonium salt) through a two-step reaction of nitration and ammoniation according to the literature (Synthesis, 2012, 44: 2058-2064).

[0039] The present invention provides a method for preparing a high-energy oxidant, the reaction equation of which is as follows:

[0040]

[0041] The specific steps are as follows:

[0042] Step 1: Dissolve LLM-116 ammonium salt (4-amino-3,5-dinitropyrazole ammonium salt) in N,N-dimethylformamide. Add potassium bromide to the solution, stir at room temperature for 0.5 h, then heat to 60–90 °C. At this temperature, add chloroacetone dropwise, maintaining the reaction at 60–90 °C for 0.5–3 h. After the reaction is complete, cool the reaction solution to room temperature, quench it with ice water, filter, wash three times with cold water, and dry to obtain 1-acetonyl-LLM-116 (1-acetonyl-4-amino-3,5-dinitropyrazole).

[0043] Step 2: Add 1-acetone-LLM-116 in portions to 98wt% concentrated sulfuric acid at 15-20℃. Cool the temperature to 0-5℃ and add fuming nitric acid dropwise, maintaining the reaction system temperature below 5℃. After the addition is complete, stir at this temperature for 1 hour. Gradually restore the reaction system to room temperature (15-30℃) over 2-3 hours, and then stir the reaction at this temperature for 4-8 hours. After the reaction is complete, pour the reaction solution into ice water to quench it, filter, remove the filter cake, and let the filtrate stand for more than 24 hours. The light yellow solid that precipitates is 1-nitroform-LLM-116 (1-nitroform-4-amino-3,5-dinitropyrazole).

[0044] Example 1:

[0045] The raw material LLM-116 ammonium salt selected in this invention was prepared according to literature (Synthesis, 2012, 44: 2058-2064) using commercially available 4-chloropyrazole as a substrate. LLM-116 ammonium salt (15 mmol, 2.85 g) was dissolved in N,N-dimethylformamide (25 mL). Potassium bromide (15 mmol, 1.79 g) was added to the solution, and the mixture was stirred at room temperature for 0.5 h. The temperature was then raised to 75 °C, and chloroacetone (22.5 mmol, 2.08 g) was added dropwise. The reaction was continued at 75 °C for 1 h. The addition of chloroacetone after raising the temperature to 75 °C was to enhance its reactivity. After the reaction was complete, the reaction solution was cooled to room temperature, quenched in ice water, filtered, washed three times with cold water, and dried to obtain 1-acetone-LLM-116 (3.28 g), with a yield of 95.5%.

[0046] 1-Acetone-LLM-116 (6 mmol, 1.37 g) was added in portions to 98 wt% concentrated sulfuric acid (10 mL) at 15–20 °C. The mixture was cooled to about 0 °C and fuming nitric acid (12 mL) was added dropwise, maintaining the reaction temperature below 5 °C. After the addition was complete, the mixture was stirred at this temperature for 1 h. The reaction system was then gradually restored to room temperature (25–30 °C) over 3 h, and then stirred at this temperature for 8 h. After the reaction was completed, the reaction solution was quenched in ice water, filtered, and the filter cake was removed. The filtrate was allowed to stand at room temperature for 24 h, and a light yellow solid precipitated was obtained, which was 0.85 g of pure 1-nitroform-LLM-116, with a yield of 44.1%.

[0047] The 1-nitroformyl-LLM-116 obtained in Example 1 was dissolved in diethyl ether and slowly evaporated at room temperature to obtain pale yellow blocky single crystals. Single crystal X-ray diffraction was performed, and its crystal structure is as follows. Figure 1 and Figure 2 As shown, its unit cell parameters are shown in the attached table below:

[0048] Appendix 1

[0049]

[0050]

[0051] The 1-nitroform-LLM-116 obtained in Example 1 was characterized, and the analytical results are as follows:

[0052] like Figure 3 The hydrogen NMR spectrum shown is shown below. 1 ¹H NMR (C3D6O): δ 8.07 ppm.

[0053] like Figure 4 The carbon NMR spectrum shown. 13 C NMR (C3D6O): δ205.47, 147.81, 132.24, 129.75ppm.

[0054] like Figure 5 The infrared spectrum shown is IR(ATR): 3674,3484,3361,2987,2901,2199,1756,1659,1633,1618,1599,1578,1539,1469, 1388,1310,1265,1224,1066,1052,975,863,838,794,758,738,691,655,639,597cm -1 Elemental analysis of C4H2N8O 10 (322.106): Measured (calculated) C 14.89 (14.92), H 0.71 (0.63), N 34.88 (34.79).

[0055] The 1-nitroform-LLM-116 obtained in Example 1 was tested and found to have an impact sensitivity of 7.5 J and a friction sensitivity of 120 N.

[0056] The carbon dioxide oxygen balance of 1-nitro-LLM-116 obtained in Example 1 was calculated to be +4.97%, and the oxygen content was 49.67%.

[0057] The density of 1-nitroform-LLM-116 obtained in Example 1 was tested to be 1.866 g·cm³. -3 It exhibits excellent detonation performance, with a calculated detonation pressure of 35.59 GPa and a detonation velocity of 9028 m / s based on EXPLO5. -1 The theoretical detonation velocity is about 10% higher than that of LLM-116.

[0058] Example 2

[0059] 1-Acetone-LLM-116 (6 mmol, 1.37 g) was added in portions to 98 wt% concentrated sulfuric acid (10 mL) at 15–20 °C. The mixture was cooled to about 0 °C and fuming nitric acid (12 mL) was added dropwise, maintaining the reaction temperature below 5 °C. After the addition was complete, the mixture was stirred at this temperature for 1 h. The reaction system was then gradually restored to room temperature (15–20 °C) over 2 h, and then stirred at this temperature for 8 h. After the reaction was completed, the reaction solution was quenched in ice water, filtered, and the filter cake was removed. The filtrate was allowed to stand at room temperature for 24 h, and a light yellow solid precipitated was 0.67 g of pure 1-nitroform-LLM-116, with a yield of 34.8%.

[0060] Comparative Example 1:

[0061] 1-Acetone-LLM-116 (6 mmol, 1.37 g) was added in portions to 98 wt% concentrated sulfuric acid (10 mL) at 15–20 °C. The mixture was cooled to about 0 °C and fuming nitric acid (12 mL) was added dropwise while maintaining the reaction temperature below 5 °C. After the addition was complete, the mixture was stirred at this temperature for 1 h. The reaction mixture was then rapidly (10 min) heated to room temperature (25–30 °C) and stirred at this temperature for 8 h. After the reaction was completed, the reaction solution was quenched in ice water, filtered, and the filter cake was removed. The filtrate was allowed to stand at room temperature for 24 h. Nuclear magnetic resonance (NMR) analysis showed that the target product 1-nitroform-LLM-116 (0.25 g) was precipitated, with a yield of 13.0%.

[0062] Comparative Example 2:

[0063] 1-Propano-LLM-116 (6 mmol, 1.37 g) was added in portions to 10 mL of 98 wt% concentrated sulfuric acid at 15–20 °C. Fuming nitric acid (12 mL) was then added dropwise to 0 °C, maintaining the reaction temperature below 5 °C. After the addition was complete, the mixture was stirred at this temperature for 1 h. The reaction mixture was then gradually restored to room temperature (25–30 °C) over 3 h, and stirred at this temperature for 8 h. At the end of the reaction, the reaction solution was quenched in ice water, filtered, and the filter cake was removed. The filtrate was rapidly stirred at room temperature for 30 min to precipitate a solid, which was then filtered, dried, and analyzed by thin-layer chromatography. Figure 6 The developing solvent was ethyl acetate:petroleum ether (1:5), which was a mixture of 1-nitro-LLM-116 and another byproduct. The mixture was separated by column chromatography with ethyl acetate:petroleum ether (1:10) to obtain 0.35 g of the target compound 1-nitro-LLM-116 (yield 18.1%) and 0.58 g of the byproduct (yield 31.9%).

[0064] As can be seen from the above implementation process, the preparation method of the 1-nitroform-LLM-116 high-energy compound of the present invention is different from the conventional nitration reaction method. Too fast a heating rate or stirring of the filtrate will lead to a decrease in product yield and an increase in by-products.

Claims

1. A method for preparing a high-energy nitroform compound, characterized in that, include: (1) The step of reacting compound 1 with chloroacetone and potassium bromide in N,N-dimethylformamide to synthesize compound 2; ； (2) The step of preparing the target product by nitrification of compound 2 in the presence of fuming nitric acid and concentrated sulfuric acid, followed by post-treatment; ； In step (2), compound 2 is added to concentrated sulfuric acid in batches at 15~20 ℃, and fuming nitric acid is added dropwise at -5~5 ℃. After the addition is complete, the mixture is stirred at this temperature for 1 h. The reaction system is gradually restored to room temperature within 2~3 h, and then stirred at this temperature for 4~8 h. The post-treatment refers to: after the nitration reaction is completed, the reaction solution is poured into ice water for quenching, filtered, the filter cake is removed, the filtrate is allowed to stand at room temperature for more than 24 hours, filtered to precipitate the precipitate, and the target product is obtained.

2. The method as described in claim 1, characterized in that, In step (1), the molar ratio of compound 1, potassium bromide and chloroacetone is 1:1:1.5; the reaction temperature is 60~90 ℃; and the reaction time is 0.5~3 h.

3. The method as described in claim 1, characterized in that, In step (2), the volume ratio of fuming nitric acid to concentrated sulfuric acid is 1~1.5:1; the volume ratio of fuming nitric acid to compound 2 is 8~10 mL:1g.

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