Combination of 1,2,4‐Oxadiazole and 1,2,5‐Oxadiazole Moieties for the Generation of High‐Performance Energetic Materials

Salts generated from linked 1,2,4‐oxadiazole/1,2,5‐oxadiazole precursors exhibit good to excellent thermal stability, density, and, in some cases, energetic performance. The design of these compounds was based on the assumption that by the combination of varying oxadiazole rings, it would be possible to profit from the positive aspects of each of the components. All of the new compounds were fully characterized by elemental analysis, IR spectroscopy, ¹H, ¹³C, and (in some cases) ¹⁵N NMR spectroscopy, and thermal analysis (DSC). The structures of 2 – 3 and 5 ‐ 1 ?5 H₂O were confirmed by single‐crystal X‐ray analysis. Theoretical performance calculations were carried out by using Gaussian 03 (Revision D.01). Compound 2 ‐ 3 , with its good density (1.85 g cm^?3), acceptable sensitivity (14 J, 160 N), and superior detonation pressure (37.4 GPa) and velocity (9046 m s^?1), exhibits performance properties superior to those of 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX).     

Synthesis of Amino,Azido, Nitro,and Nitrogen‐Rich Azole‐Substituted Derivatives of 1H‐Benzotriazole for High‐Energy Materials Applications

The amino, azido, nitro, and nitrogen‐rich azole substituted derivatives of 1H‐benzotriazole have been synthesized for energetic material applications. The synthesized compounds were fully characterized by ¹H and ¹³C NMR spectroscopy, IR, MS, and elemental analysis. 5‐Chloro‐4‐nitro‐1H‐benzo[1,2,3]triazole ( 2 ) and 5‐azido‐4,6‐dinitro‐1H‐benzo[1,2,3]triazole ( 7 ) crystallize in the Pca2₁ (orthorhombic) and P2₁/c (monoclinic) space group, respectively, as determined by single‐crystal X‐ray diffraction. Their densities are 1.71 and 1.77 g cm^?3, respectively. The calculated densities of the other compounds range between 1.61 and 1.98 g cm^?3. The detonation velocity (D) values calculated for these synthesized compounds range from 5.45 to 8.06 km s^?1, and the detonation pressure (P) ranges from 12.35 to 28 GPa.     

Energetic Salts Based on Furazan‐Functionalized Tetrazoles: Routes to Boost Energy

Based on the backbone of the furazan‐tetrazole structure, routes were developed to improve the properties of energetic materials. Two types of high‐density energetic salts were designed, prepared, and fully characterized. Single‐crystal X‐ray analyses support the structural characteristics for two amino salts. A majority of the salts exhibited good detonation properties, high thermal stabilities, and relatively low impact and friction sensitivities. Hydroxylammonium and hydrazinium salts, 1 – 3 and 1 – 4 , which have relatively high densities (1.84 and 1.74 g cm^?3,, respectively), acceptable impact and friction sensitivities (14 J, 160 N and 28 J, 360 N), and good detonation pressures (38.3 and 32.2 GPa) and velocities (9323 and 9094 m s^?1), have performance properties superior to 1,3,5‐trinitro‐1,3,5‐triazinane (RDX) and triaminotrinitrobenzene (TATB).     

Theoretical Study of the N-NO2 Bond Dissociation Energies for Energetic Materials with Density Functional Theory

The N-NO2 bond dissociation energies （BDEs） for 7 energetic materials were computed by means of accurate density functional theory （B3LYP, B3PW91 and B3P86） with 6-31G＊＊ and 6-311G＊＊ basis sets. By comparing the computed energies and experimental results, we find that the B3P86/6-311G＊＊ method can give good results of BDE, which has the mean absolute deviation of 1.30kcal/mol. In addition, substituent effects were also taken into account. It is noted that the Hammett constants of substituent groups are related to the BDEs of the N-NO2 bond and the bond dissociation energies of the energetic materials studied decrease when increasing the number of NO2 group.     

3-氨基-4-硝基氧化呋咱含能化合物的设计合成研究

在氧化呋咱环上引入氨基或硝基等功能基团,可提高含能化合物的能量密度和爆炸性能。为了获得更高能量密度的新型含能化合物,本文利用密度泛函理论（DFT）和单、双激发的耦合簇（CCSD）方法探索了以3-酰基叠氮基-4硝基氧化呋咱为起始材料,在二氧六环和水混合溶剂中合成3-氨基-4硝基氧化呋咱的反应机理,给出了反应的势能曲线。结果表明,该反应主要分为两个阶段：3-酰基叠氮基-4硝基氧化呋咱脱N₂后进行Curtious重排产生异氰酸酯;异氰酸酯经水解、羟基扭转、CO₂的脱离形成产物。反应的决速步为CO₂的脱离,能垒为44kcal/mol。因此,加热是实现该合成反应的必要条件。水既绿色环保,又参与反应,是该反应的最佳溶剂。这些结果为3-氨基-4-硝基氧化呋咱的实验合成提供了必要的理论依据。     

Kinetic Stability and Propellant Performance of Green Energetic Materials

A thorough theoretical investigation of four promising green energetic materials is presented. The kinetic stability of the dinitramide, trinitrogen dioxide, pentazole, and oxopentazole anions has been evaluated in the gas phase and in solution by using high‐level ab initio and DFT calculations. Theoretical UV spectra, solid‐state heats of formation, density, as well as propellant performance for the corresponding ammonium salts are reported. All calculated properties for dinitramide are in excellent agreement with experimental data. The stability of the trinitrogen dioxide anion is deemed sufficient to enable synthesis at low temperature, with a barrier for decomposition of approximately 27.5 kcal mol^?1 in solution. Oxopentazolate is expected to be approximately 1200 times more stable than pentazolate in solution, with a barrier exceeding 30 kcal mol^?1, which should enable handling at room temperature. All compounds are predicted to provide high specific impulses when combined with aluminum fuel and a polymeric binder, and rival or surpass the performance of a corresponding ammonium perchlorate based propellant. The investigated substances are also excellent monopropellant candidates. Further study and attempted synthesis of these materials is merited.     

Triazole‐Substituted Nitroarene Derivatives: Synthesis,Characterization, and Energetic Studies

A series of dense and energetic polynitroaryl‐1,2,4‐triazoles were synthesized through the nitration of aryl‐1,2,4‐triazoles. The Cu‐catalyzed/base‐mediated coupling reactions of haloarenes with 1,2,4‐triazoles delivered N‐aryl‐1,2,4‐triazoles. These new nitro‐rich‐aryltriazoles were characterized by analytical and spectroscopic methods. The solid‐state structures of most of these compounds were established by X‐ray diffraction analysis. Their thermal properties were determined by differential scanning calorimetry–thermogravimetric analysis. Their heats of formation (HOFs) and crystal densities were also calculated. The densities of the synthesized compounds ranged from 1.40 to 1.85 g cm^?3. Some of these newly synthesized compounds exhibited high positive HOFs, good thermal stabilities, high densities, and reasonable detonation velocities and pressures.     

Enhancing Energetic Properties and Sensitivity by Incorporating Amino and Nitramino Groups into a 1,2,4‐Oxadiazole Building Block

A single nitrogen‐rich heterocyclic ring with many energetic groups is expected to exhibit excellent detonation performance. We report an effective approach for the synthesis of 3‐amino‐5‐nitramino‐1,2,4‐oxadiazole, which has nitramino and amino groups in the same building block. The single‐crystal X‐ray structure shows layered hydrogen‐bonding pairs as well as the presence of a water molecule which ensure insensitivity. Through incorporation of a cation, the hydrazinium or hydroxylammonium salts exhibit good energetic performance and acceptable sensitivities.     

含能材料的密度、爆速、爆压和静电感度的理论研究

用密度泛函理论(DFT) B3LYP方法, 在6-31G*基组水平下, 全优化计算了系列硝胺类和硝基芳烃类爆炸物的几何构型, 用Monte-Carlo方法和自编程序, 基于0.001 e•bohr^－3等电子密度面所包围的体积空间求得分子平均摩尔体积(V)和理论密度(ρ). 用Kamlet-Jacobs方程基于理论密度(ρ)和PM3计算生成焓(ΔH_f)估算标题物的爆速(D)和爆压(p), 发现多环硝胺类化合物的爆轰性能优于芳烃硝基类化合物, 故此, 在寻求高能量密度材料(HEDM)时, 我们应特别关注多环硝胺化合物. 与ρ和D文献值比较, 表明本理论计算方法和结果是适用可靠的. 将爆速(D)和爆压(p)计算值与静电感度实验值(E_ES)进行比较和关联, 发现: 若对化合物进行细致分类讨论, 则它们之间存在较好的线性关系. 据此建议, 在含能材料分子设计中, 可通过理论计算爆轰性质(D或p)去预估难以定量求得或尚未合成的含能材料的静电火花感度值(E_ES). 此外, 我们还讨论了取代基对ρ, D和p的影响, 也有助于分子设计.     

Energetic salts based on dipicrylamine and its amino derivative

Energetic salts based on dipicrylamine and its amino derivative were synthesized. All salts were fully characterized by multinuclear NMR spectroscopy ((1)H, (13)C), vibrational spectroscopy (IR), and elemental analysis. Ethylenediammonium di-DPA (DPA=dipicrylamine) and 1,3-diaminoguanidinium DPA were further confirmed by single-crystal X-ray diffraction. These salts exhibit reasonable physical properties, such as high densities (1.71-1.81 g cm(-3)), good thermal stabilities (T(d) =155-285 °C), and low solubilities in water. The impact sensitivity of 1-methyl-3,4,5-triamino-1,2,4-triazolium DPA is lower than that of 2,4,6-trinitrotoluene (TNT), and for some other energetic salts their impact sensitivities are comparable to that of TNT. Based on experimental densities and theoretical calculations carried out by using the Gaussian 03 suite of programs, all the salts have calculated detonation pressures (22.5-27.8 GPa) and velocities (7226-7917 m s(-1)) that exceed those of conventional TNT. The toxicities of these salts measured by luminescent bacteria toxicity tests are much lower than that of TNT, and two binary eutectic mixtures with melting points that fall between 70 and 100 °C were identified.     

Comparative Study of Various Pyrazole‐based Anions: A Promising Family of Ionic Derivatives as Insensitive Energetic Materials

In the design of advanced energetic materials, high‐density explosophores play a pivotal role because of their remarkable enhancement of both density and molecular stability. Using diversified functionalization strategies, a comparative study involving various nitropyrazole anions shows that these are crucially important in determining performance and stability. A promising family of pyrazole‐based energetic ionic derivatives were synthesized and characterized by NMR and IR spectroscopies, and elemental analysis. Among them, 7 , 8 , 11 – 13 exhibit favorable overall performance as energetic materials.     

Dimethoxycarbonyl Groups Surrounding a Symmetric Diaminobistetrazole Ring: Exploring New Green Energetic Materials

A novel oxygen‐containing dimethoxycarbonyl diaminobistetrazole ( 1 ) was synthesized via a facile strategy. The sodium salt ( 2 ) based on this ligand was prepared and these two compounds were fully characterized by using elemental analysis, IR and mass spectrometry and single‐crystal X‐ray diffraction. Their density, heats of formation, thermal stability and sensitivity, as well as the energetic properties from EXPLO5 code were investigated. These newly synthesized compounds possess high positive heats of formation and detonation heats. Compound 1 exhibits good detonation performance and acceptable stability, and might be a potential eco‐friendly alternative of lead azide. The present study contributes to the development of tetrazole derivatives as new energetic materials.     

Furazans with Azo Linkages: Stable CHNO Energetic Materials with High Densities,Highly Energetic Performance,and Low Impact and Friction Sensitivities

Various highly energetic azofurazan derivatives were synthesized by simple and efficient chemical routes. These nitrogen‐rich materials were fully characterized by FTIR spectroscopy, elemental analysis, multinuclear NMR spectroscopy, and high‐resolution mass spectrometry. Four of them were further confirmed structurally by single‐crystal X‐ray diffraction. These compounds exhibit high densities, ranging from 1.62 g cm^?3 up to a remarkably high 2.12 g cm^?3 for nitramine‐substituted azofurazan DDAzF ( 2 ), which is the highest yet reported for an azofurazan‐based CHNO energetic compound and is a consequence of the formation of strong intermolecular hydrogen‐bonding networks. From the heats of formation, calculated with Gaussian 09, and the experimentally determined densities, the energetic performances (detonation pressure and velocities) of the materials were ascertained with EXPLO5 v6.02. The results suggest that azofurazan derivatives exhibit excellent detonation properties (detonation pressures of 21.8–46.1 GPa and detonation velocities of 6602–10 114 m s^?1) and relatively low impact and friction sensitivities (6.0–80 J and 80–360 N, respectively). In particular, they have low electrostatic spark sensitivities (0.13–1.05 J). These properties, together with their high nitrogen contents, make them potential candidates as mechanically insensitive energetic materials with high‐explosive performance.     

Energetic nitrogen-rich salts and ionic liquids

Energetic salts offer many advantages over conventional energetic molecular compounds. The use of nitrogen containing anions and cations contributes to high heats of formations and high densities. Their low carbon and hydrogen content gives rise to a good oxygen balance. The decomposition of these compounds is predominantly through the generation of dinitrogen which makes them very promising candidates for highly energetic materials for industrial or military applications.     

Bis(4‐nitraminofurazanyl‐3‐azoxy)azofurazan and Derivatives: 1,2,5‐Oxadiazole Structures and High‐Performance Energetic Materials

Bis(4‐nitraminofurazanyl‐3‐azoxy)azofurazan ( 1 ) and ten of its energetic salts were prepared and fully characterized. Computational analysis based on isochemical shielding surface and trigger bond dissociation enthalpy provide a better understanding of the thermal stabilities for nitramine‐furazans. These energetic compounds exhibit good densities, high heats of formation, and excellent detonation velocity and pressure. Some representative compounds, for example, 1 (v_D: 9541 m s^?1; P: 40.5 GPa), and 4 (v_D: 9256 m s^?1; P: 38.0 GPa) exhibit excellent detonation performances, which are comparable with current high explosives such as RDX (v_D: 8724 m s^?1; P: 35.2 GPa) and HMX (v_D: 9059 m s^?1; P: 39.2 GPa).     

A Theoretical Study on the Structure,Intramolecular Interactions,and Detonation Performance of Hydrazinium Dinitramide

The structures of hydrazinium dinitramide (HDN) in the gas phase and in aqueous solution have been studied at different levels of theory by using quantum chemistry. The intramolecular hydrogen‐bond interactions in HDN were studied by employing the quantum theory of atoms in molecules (QTAIM), as well as those in ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), and ammonium nitroformate (ANF) for comparison. The results showed that HDN possessed the strongest hydrogen bonds, with the largest hydrogen‐bond energy (?47.95 kJ mol^?1) and the largest total hydrogen‐bond energy (?60.29 kJ mol^?1). In addition, the charge transfer between the cation and the anion, the binding energy, the energy difference between the frontier orbitals, and the second‐order perturbation energy of HDN were all the largest among the investigated compounds. These strongest intramolecular interactions accounted for the highest decomposition temperature of HDN among all four compounds. The IR spectra in the gas phase and in aqueous solution were very different and showed the significant influence of the solvent. The UV spectrum showed the strongest absorption at about 253 nm. An orbital‐interaction diagram demonstrated that the transition of electrons mainly happened inside the anion of HDN. The detonation velocity (D=8.34 km s^?1) and detonation pressure (P=30.18 GPa) of HDN were both higher than those of ADN (D=7.55 km s^?1 and P=24.83 GPa). The composite explosive HDN/CL‐20 with the weight ratio w_CL?20/w_HDN=0.388:0.612 showed the best performance (D=9.36 km s^?1, P=39.82 GPa), which was close to that of CL‐20 (D=9.73 km s^?1, P=45.19 GPa) and slightly better than that of the composite explosive ADN/CL‐20 (w_CL?20/w_ADN=0.298:0.702, D=9.34 km s^?1, P=39.63 GPa).     

3,6‐Dinitropyrazolo[4,3‐c]pyrazole‐Based Multipurpose Energetic Materials through Versatile N‐Functionalization Strategies

A family of 3,6‐dinitropyrazolo[4,3‐c]pyrazole‐based energetic compounds was synthesized by using versatile N‐functionalization strategies. Subsequently, nine ionic derivatives of the N,N′‐(3,6‐dinitropyrazolo[4,3‐c]pyrazole‐1,4‐diyl)dinitramidate anion were prepared by acid‐base reactions and fully characterized by infrared, multinuclear NMR spectra, and elemental analysis. The structures of four of these compounds were further confirmed by single‐crystal X‐ray diffraction. Based on their different physical and detonation properties, these compounds exhibit promising potential as modern energetic materials and can be variously classified as green primary explosives, high‐performance secondary explosives, fuel‐rich propellants, and propellant oxidizers.