Nitrogen-rich Energetic Compound Research Articles

Taming of Triazole, Tetrazole, and Azido Groups: Nitrogen-Rich Energetic Materials with High Thermal Stabilities.

Nitrogen-rich energetic materials are of interest due to their potential use as high-energy-density materials in various applications. However, most compounds with a high nitrogen content show poor thermal stabilities, which may limit their use in certain applications. In pursuit of nitrogen-rich energetic materials, this study presents the synthesis and characterization of two nitrogen rich energetic compounds, namely 3-azido-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-amine (3, C3H3N11, N%: 79.78) and (E)-1,2-bis(3-azido-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-yl) diazene (7, C6H2N22, N%: 80.62). Compounds 3 and 7 have high thermal stabilities of 216 and 221 °C, respectively, making them the most thermally stable among metal-free primary explosives. Additionally, they show good energetic performance (vD: 8345 m s-1; P: 25.17 GPa; vD: 8275 m s-1; P: 25.57 GPa), making them potential candidates for metal-free high energy primary explosive. The energetic salts of 3 and 7 were also investigated. Among them, hydrazinium salt 11 displays better energetic performance (vD: 9089 m s-1; P: 30.55 GPa), which was on par with those of cyclotetramethylene tetranitramine (HMX). This research contributes to the exploration of nitrogen-rich energetic materials with potential applications in various fields.

Construction of Nitrogen-Rich Energetic Isomers Containing Multiple Hydrogen Bond Networks.

Nitrogen-rich energetic materials have been the focus of a few studies on their isomers. Novel nitrogen-rich energetic compounds TZ, DTZ, and NTZ were synthesized through simple steps. The hydrogen bond networks significantly enhanced their properties (TZ, Td = 290 °C and Dv = 8370 m s-1; DTZ, Td = 282 °C and Dv = 8392 m s-1; and NTZ, Td = 272 °C and Dv = 8762 m s-1), which are superior to their isomers. This realized a balance between the energy and stability of polycyclic tetrazoles, providing insights for high-performance energetic materials.

Symmetric Refunctionalization of Diaminodinitropyrazine with Hydrazine and Aminotetrazole: Strategy for Enhancing Detonation Performance and Safety in Energetic Materials.

Two novel nitrogen-rich green energetic compounds were synthesized for the first time from readily available and cost-effective pyrazine starting materials. All newly synthesized molecules were comprehensively characterized, including infrared spectroscopy, nuclear magnetic resonance, elemental analysis, mass spectrometry, and thermogravimetric analysis-differential scanning calorimetry. All compounds have additionally been validated by single-crystal X-ray diffraction analysis. The physicochemical properties of compounds 2, 4, and 5 were thoroughly investigated. Notably, all compounds exhibit remarkable performance, such as a high density (>1.84 g cm-3), excellent detonation properties (VOD > 8582 m s-1, and DP > 31.3 GPa), outstanding thermostability (>205 °C), and high insensitivity (IS > 35 J, and FS = 360 N). These attributes are quite comparable to those of secondary benchmark explosives such as TATB, RDX, LLM-105, and FOX-7. This tuned performance evidences that the incorporation of hydrazine, nitro, and aminotetrazole into the pyrazine framework fosters robust nonbonded interactions, ultimately enhancing thermal stability and reducing sensitivity. The findings of this study not only signify that compounds 2 and 5 have excellent detonation properties and stability but also prove that the strategy of replacing amino groups with hydrazine and aminotetrazole is a practical means of developing new insensitive energetic materials.

Assessment of electrostatic discharge sensitivity of nitrogen-rich heterocyclic energetic compounds and their salts as high energy-density dangerous compounds: A study of structural variables

Nitrogen-rich heterocyclic energetic compounds (NRHECs) and their salts have witnessed widespread synthesis in recent years. The substantial energy-density content within these compounds can lead to potentially dangerous explosive reactions when subjected to external stimuli such as electrical discharge. Therefore, developing a reliable model for predicting their electrostatic discharge sensitivity (ESD) becomes imperative. This study proposes a novel and straightforward model based on the presence of specific groups (–NH2 or -NH-, −N=N+−O− and –NNO2, -ONO2 or -NO2) under certain conditions to assess the ESD of NRHECs and their salts, employing interpretable structural parameters. Utilizing a comprehensive dataset comprising 54 ESD measurements of NRHECs and their salts, divided into 49/5 training/test sets, the model achieves promising results. The Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Maximum Error for the training set are reported as 0.16 J, 0.12 J, and 0.5 J, respectively. Notably, the ratios RMSE(training)/RMSE(test), MAE(training)/MAE(test), and Max Error(training)/Max Error(test) are all greater than 1.0, indicating the robust predictive capabilities of the model. The presented model demonstrates its efficacy in providing a reliable assessment of ESD for the targeted NRHECs and their salts, without the need for intricate computer codes or expert involvement.

Synthesis and Characterization of Azido-Functionalized 1,2,3-Triazole and Fused 1,2,3-Triazole.

Here, we report the nitration of NH on the 1,2,3-triazole ring and the synthesis of several nitrogen-rich energetic compounds based on key intermediate 4-azido-5-(chlorodinitromethyl)-2-nitro-2H-1,2,3-triazole (5). Starting from 4-amino-1H-1,2,3-triazole-5-carbonitrile (1), we successfully constructed compound 5 through four steps. Subsequently, the dechlorination of compound 5 gave potassium 4-azido-5-(dinitromethyl)-2H-1,2,3-triazole (6) (IS = 1 J, vD = 8802 m s-1). Additionally, diammonium (8) and dihydrazinium (9) salts based on 4-azido-5-(dinitromethyl)-2H-1,2,3-triazole were also successfully synthesized and characterized. A novel fused nitrogen-rich heterocycle, namely, 6H-[1,2,3]triazolo[4,5-d][1,2,3] triazine-6,7-diamine (10), was surprisingly obtained, which has a high nitrogen content of 73.66% and shows good thermal stability (Tdec = 203 °C) and insensitivity to mechanical stimuli, while the detonation velocity (vD) and detonation pressure (P) reach 8421 m s-1 and 26.0 GPa, respectively.

Combining the advantages of 1,3,4-oxadiazole and tetrazole enables achieving high-energy insensitive materials.

Combining the advantages of energetic heterocycles to achieve high-energy insensitive explosives is a significant challenge. Herein, based on high-energy tetrazole rings and highly stable 1,3,4-oxadiazole rings, a series of novel nitrogen rich energetic compounds 5-9 were successfully constructed. The related compounds were fully characterized by EA, FT-IR, NMR, DSC, and MS, and compounds 6-9 were further confirmed by X-ray single crystal diffraction. Among them, the energetic ion salts 6-8 show high thermal stability (Tdec > 250 °C) and low mechanical sensitivity (IS > 40 J, FS > 360 N), as well as good energy properties (7552-8050 m s-1, 19.4-23.3 GPa). In particular, the azo compound 9 exhibits competent comprehensive performances (Tdec = 226.2 °C, D = 8502 m s-1, P = 28.9 GPa, IS = 32 J, FS = 320 N). These results suggest that the strategy of integrating tetrazole and 1,3,4-oxadiazole and employing an azo structure as a bridging unit are effective approaches to construct high-energy insensitive materials.

Triazene-bridged energetic materials based on nitrotriazole: synthesis, characterization, and laser-ignited combustion performance.

Compared to the widely concerned azo bridges (-NN-), triazene bridges (-NN-NH-) with longer nitrogen chains are also favorable linking units leading to novel energetic materials. In this work, a new family of nitrogen-rich nitrotriazolate-based energetic compounds with a triazene bridge were synthesized and well characterized. The experimental results indicated that most of these new compounds have good thermal stabilities and low sensitivities. Among these, ammonium 5,5'-dinitro-3,3'-triazene-1,2,4-triazolate (3) and potassium 5-nitro-3,3'-triazene-1,2,4-triazolate (7) decomposed at a relatively high temperature (240.6 °C for 3 and 286.9 °C for 7). The impact sensitivities of the obtained compounds ranged from 15 J to 45 J. They also have relatively high positive heats of formation between 667.5 to 817.3 kJ mol-1. The calculated detonation pressures (P) were located between 23.7 and 34.8 GPa, and the calculated detonation velocities (D) were between 8011 and 9044 m s-1. Interestingly, ammonium 5-nitro-3,3'-triazene-1,2,4-triazolate (8) and hydroxylammonium 5-nitro-3,3'-triazene-1,2,4-triazole (10) possessed excellent laser-ignited combustion performance.

Enhanced combustion behavior of TKX-50/B/NC composites via electrospray

ABSTRACT TKX-50, as a representative of a new nitrogen-rich energetic compound, has attracted extensive interests due to its high energy and low sensitivity properties. As an important energetic material, combustible agent has great influence on improving the energy level of explosives and propellants. Boron powder has become the most potential combustible agent in energetic fields because of its unique performances. In this work, nano-boron-based microspheres containing TKX-50 are directly fabricated by electrospray deposition. The prepared microspheres showed high monodispersity with particle size ranging from ~1–3 μm. Thermal behavior results show that the mass gain of the electrostatically sprayed sample is 163.3%, which is much higher than that of pure boron and physically mixed samples. Combustion behavior tests show that electrosprayed microspheres exhibit outstanding performance in comparison to physical mixed sample, the peak pressure improved by 85%, the burning time decreased by 21% and the pressurization rate improved by 136%. These excellent properties are probably related to their uniform microstructure. Therefore, electrospray preparation of microspheres with controllable structure has a good application prospect in energetic materials.

Synthetic Strategies Toward Nitrogen-Rich Energetic Compounds Via the Reaction Characteristics of Cyanofurazan/Furoxan.

The structural units of amino-/cyano-substituted furazans and furoxans played significant roles in the synthesis of nitrogen-rich energetic compounds. This account focused on the synthetic strategies toward nitrogen-rich energetic compounds through the transformations based on cyanofurazan/furoxan structures, including 3-amino-4-cyanofurazan, 4-amino-3-cyano furoxan, 3,4-dicyanofurazan, and 3,4-dicyanofuroxan. The synthetic strategies toward seven kinds of nitrogen-rich energetic compounds, such as azo (azoxy)-bridged, ether-bridged, methylene-bridged, hybrid furazan/furoxan-tetrazole–based, tandem furoxan–based, hybrid furazan-isofurazan–based, hybrid furoxan-isoxazole–based and fused framework–based energetic compounds were fully reviewed, with the corresponding reaction mechanisms toward the nitrogen-rich aromatic frameworks and examples of using the frameworks to create high energetic substances highlighted and discussed. The energetic properties of typical nitrogen-rich energetic compounds had also been compared and summarized.

Nitrification Progress of Nitrogen-Rich Heterocyclic Energetic Compounds: A Review.

As a momentous energetic group, a nitro group widely exists in high-energy-density materials (HEDMs), such as trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), etc. The nitro group has a significant effect on improving the oxygen balance and detonation performances of energetic materials (EMs). Moreover, the nitro group is a strong electron-withdrawing group, and it can increase the acidity of the acidic hydrogen-containing nitrogen-rich energetic compounds to facilitate the construction of energetic ionic salts. Thus, it is possible to design nitro-nitrogen-rich energetic compounds with adjustable properties. In this paper, the nitration methods of azoles, including imidazole, pyrazole, triazole, tetrazole, and oxadiazole, as well as azines, including pyrazine, pyridazine, triazine, and tetrazine, have been concluded. Furthermore, the prospect of the future development of nitrogen-rich heterocyclic energetic compounds has been stated, so as to provide references for researchers who are engaged in the synthesis of EMs.

Computational design of a notable nitrogen-rich energetic compound on the basis of Diels–Alder reactions

A notable nitrogen-rich energetic compound EC-1 was constructed by screening the most suitable diene and exploring the origin of the reactivity difference of Diels–Alder reactions.

Some Nitrogen Rich Energetic Material Synthesis by Nucleophilic Substitution Reaction from Polynitro Aromatic Compounds.

Three new nitrogen-rich energetic compounds, N-(5-chloro-2,4-dinitrophenyl)hydrazine (1), N-(5-chloro-2,4-dinitrophenyl)guanidine (2) and N-(5-chloro-2,4-dinitrophenyl)-4-aminopyrazole (3) prepared by the nucleophilic substitution reaction of 1,3-dichloro-4,6-dinitrobenzene with hydrazine, guanidinium carbonate and 4-aminopyrazole. The compounds were characterized by 1H NMR, 13C NMR, IR and mass spectroscopy. Only compound 2 could be prepared in a suitable crystal and molecular model was determined by X-ray analysis. Compounds were investigated by TG and DSC. Thermal degradation and thermokinetic behavior were investigated by Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose techniques. Compounds were observed to be prone to exothermical thermal decomposition. HOMO and LUMO levels, theoretical formation enthalpy and electrostatic maps were calculated by Gaussian09. The detonation velocity and pressure were calculated by Kamlet-Jacobs equation. The compounds were assayed for antimicrobial properties.

Synthesis and characterization of pyrazole- and imidazole- derived energetic compounds featuring ortho azido/nitro groups

Two novel nitrogen-rich heterocyclic energetic compounds, 5-amino-3-azido-4-nitro-1H-pyrazole (3) and 5,5′-diazido-4,4′-dinitro-1H,1′H-2,2′-biimidazole(6), featuring ortho azido/nitro groups were designed and synthesized by reactions of diazonium salts with sodium azide. In addition, treatment of diazonium salts with a mixture of hydrazine monohydrate and sodium nitrite in acetic acid also gave the same products 3 and 6 in high yields. Both structures of the products were characterized by 1H NMR, 13C NMR, IR and elemental analysis, as well as single-crystal X-ray diffraction. Furthermore, their physicochemical and energetic properties were studied.

Synthetic optimization of TACOT-derived nitrogen-rich energetic compounds and reaction mechanism research

High-nitrogen energetic compounds are widely used in military and civil fields. To cope with some special conditions, materials with high melting point and good heat resistance are required. Herein, synthetic approach of two TACOT-derived compounds with high heat resistance and strong insensitivity for friction has been optimized. Significantly, 100 g-scale of aza-TACOT(I) was prepared with a total yield of 80% and a purity of 99.9%. Meanwhile, aza-TACOT(II) was obtained with a purity of 98.9% under the optimized conditions. This practical method features scalable and simple operations. In addition, an acceptable mechanism was firstly proposed for the critical step.

Tunable Dimroth rearrangement of versatile 1,2,3-triazoles towards high-performance energetic materials

A highly efficient strategy of two different types of nitrogen-rich heterocyclic energetic compounds, featuring a single NH-bridge (–NH–) and a fused ring, was demonstrated by virtue of Dimroth rearrangement reactions.

Melamine N-oxide based self-assembled energetic materials with balanced energy & sensitivity and enhanced combustion behavior

Development of advanced energetic materials with promising properties has been intensely-pursued over the past decades. However, traditional strategies for integrating fuel skeleton and oxidizing groups into an organic molecule are very difficult to balance the contradictory relationship between high energy and low sensitivity of energetic materials. In this work, we present a promising approach to develop advanced energetic materials through intermolecular assembly of nitrogen-rich triazine energetic compounds and high-energy oxidants. Under the direction of electrostatic potential and proton affinity calculations, a novel energetic compound 2,4,6-triamino-1,3,5-triazine-1,3-dioxide (TTDO) was rationally designed and synthesized. The easy and effective self-assembly of TTDO with high-energy oxidants afforded a series of novel advanced energetic materials with a good balance between energy and sensitivity. Among these self-assembled energetic materials, TTDOP (a self-assembled energetic material between TTDO and HClO4) showed a very high density (2.047 g cm−3 at 100 K), detonation properties (9284 m s−1 and 41 GPa) as high as that of HMX and better mechanical sensitivity (13 J and 144 N). Moreover, TTDOP exhibited great promise as a substitute for ammonium perchlorate (AP) in solid propellant formulations due to its high combustion and propulsion performances. This work opens a new avenue to develop intermolecular energetic materials with well balanced energy & sensitivity and versatile functionality.

TACOT-derived new nitrogen rich energetic compounds: synthesis, characterization and properties

Two novel TACOT derivatives, compounds 7 and 8, were synthesized and characterized. Compound 7 is suggested as a heat-resistant explosive, and compound 8 is a potential nitrogen-rich high energetic material with excellent positive heat of formation of 1053 kJ mol−1.

Thermochemistry, Tautomerism, and Thermal Decomposition of 1,5-Diaminotetrazole: A High-Level ab Initio Study.

Thermochemistry, kinetics, and mechanism of thermal decomposition of 1,5-diaminotetrazole (DAT), a widely used "building block" of nitrogen-rich energetic compounds, were studied theoretically at a high and reliable level of theory (viz., using the explicitly correlated CCSD(T)-F12/aug-cc-pVTZ procedure). Quantum chemical calculations provided detailed insight into the thermolysis mechanism of DAT missing in the existing literature. Moreover, several contradictory assumptions on the mechanism and key intermediates of thermolysis were resolved. The unimolecular primary decomposition reactions of the seven isomers of DAT were studied in the gas phase and in the melt using a simplified model of the latter. The two-step reaction of N2 elimination from the diamino tautomer was found to be the primary decomposition process of DAT in the gas phase and melt. The effective Arrhenius parameters of this process were calculated to be E a = 43.4 kcal mol-1 and log( A/s-1) = 15.2 in a good agreement with the experimental values. Contrary to the existing literature data, all other decomposition channels of DAT isomers turned out to be kinetically unimportant. Apart from this, a new primary decomposition channel yielding N2, cyanamide, and 1,1-diazene was found for some H-bonded dimers of DAT. We also determined a reliable and mutually consistent set of thermochemical values for DAT (Δ f H solid0 = 74.5 ± 1.5 kcal·mol-1) by combining theoretically calculated (W1 multilevel procedure along with an isodesmic reaction) gas phase enthalpy of formation (Δ f H gas0 = 100.7 ± 1.0 kcal·mol-1) and experimentally measured sublimation enthalpy (Δ sub H0 = 26.2 ± 0.5 kcal·mol-1).

Asymmetric nitrogen-rich energetic materials resulting from the combination of tetrazolyl, dinitromethyl and (1,2,4-oxadiazol-5-yl)nitroamino groups with furoxan.

Three classes of nitrogen-rich energetic compounds 7-9 (combination of tetrazolyl, dinitromethyl and furoxan), 12-17 (combination of tetrazolyl, (1,2,4-oxadiazol-5-yl)nitroamino and furoxan) and 20-22 (combination of dinitromethyl, (1,2,4-oxadiazol-5-yl)nitroamino and furoxan) were obtained by selected reactions with 3,4-dicyano-furoxan. All the new compounds were thoroughly characterized by IR, NMR [1H, 13C{1H}], elemental analysis, and differential scanning calorimetry (DSC). Compounds 7, 13, 20 and 22 were also further characterized with single-crystal X-ray diffraction studies. Heats of formation and detonation performances for nine compounds were determined using Gaussian 03 and EXPLO5 v6.01 programs, showing that 15 as a secondary explosive is superior to 1,3,5-trinitrotriazacyclohexane (RDX) and 20 is a promising green primary explosive.

Prediction of enthalpies of sublimation of high-nitrogen energetic compounds: Modified Politzer model

In the framework of the Politzer approach, the improved electrostatic potential model for estimating enthalpies of sublimation of nitrogen-rich energetic compounds is proposed on the basis of reliable experimental enthalpies of sublimation for 185 compounds. The accuracy of predicted values is estimated to be within ±20kJ/mol. The model was applied to estimate the solid phase enthalpies of formation of some tetrazole-, tetrazine-, furazan-, and furoxan-based energetic compounds.