Diazotization of o-Aminoamidoximes for the Preparation of Energetic 6,5,6-Fused 1,2,3-Triazine-3-oxides

Two 6,5,6-fused 1,2,3-triazine-3-oxides (4 and 6) were designed and synthesized via the reaction of o-aminoamidoximes with sodium nitrite. In addition, the ring-opening products (5, 7, and 8) derived from 1,2,3-triazine-3-oxides were isolated and characterized. A comprehensive exploration of the reaction mechanism governing the ring-opening process was performed through a combination of theoretical and experimental studies. Notably, compound 4 exhibited commendable detonation properties and low sensitivity, demonstrating its promising potential as an energetic material.

Chemical Descriptors for a Large-Scale Study on Drop-Weight Impact Sensitivity of High Explosives

The drop-weight impact test is an experiment that has been used for nearly 80 years to evaluate handling sensitivity of high explosives. Although the results of this test are known to have large statistical uncertainties, it is one of the most common tests due to its accessibility and modest material requirements. In this paper, we compile a large data set of drop-weight impact sensitivity test results (mainly performed at Los Alamos National Laboratory), along with a compendium of molecular and chemical descriptors for the explosives under test. These data consist of over 500 unique explosives, over 1000 repeat tests, and over 100 descriptors, for a total of about 1500 observations. We use random forest methods to estimate a model of explosive handling sensitivity as a function of chemical and molecular properties of the explosives under test. Our model predicts well across a wide range of explosive types, spanning a broad range of explosive performance and sensitivity. We find that properties related to explosive performance, such as heat of explosion, oxygen balance, and functional group, are highly predictive of explosive handling sensitivity. Yet, models that omit many of these properties still perform well. Our results suggest that there is not one or even several factors that explain explosive handling sensitivity, but that there are many complex, interrelated effects at play.

Imidazole-Based Energetic Materials: A Promising Family of N-Heterocyclic Framework

Imidazole represents a fascinating class of explosophoric units with exciting structures and unique properties. As compared to other nitrogen-rich heterocycles, imidazole demonstrates great potential applications due to economic effectiveness and superior energetic performances. The field of traditional chemistry has been extensively explored for imidazole, and thus established bond-building methods and functionalization strategies promote further development as high-energy density materials (HEDMs). This review addresses the development of energetic imidazole compounds in the past decade, summarizes their physiochemical properties, and is divided into three parts (explosives, propellants, and energetic biocides) according to application requirements. Various synthetic strategies for these energetic molecules are highlighted, including the construction of heterocyclic frameworks and following functionalization. The selected and discussed reactions illustrate the versatility of imidazole in energetic applications as building blocks for the future design of new HEDMs.

Synthesis and Characterization of Binary, Highly Endothermic, and Extremely Sensitive 2,2'-Azobis(5-azidotetrazole)

2,2'-Azobis(5-azidotetrazole) (C₂N₁₆, 3), a highly energetic nitrogen-rich binary CN compound was obtained in a three-step synthesis through the formation of 5-azidotetrazole (1), subsequent amination using O-tosylhydroxylamine to give 2-amino-5-azidotetrazole (2), and oxidative azo coupling of 2 using tBuOCl as an oxidant in MeCN. A nitrogen:carbon ratio of 8:1, eight nitrogen atoms in a row, and a nitrogen content of over 90% was unknown for a binary heterocyclic compound until now. The successful isolation was confirmed through X-ray diffraction as well as by vibrational and ¹³C NMR spectroscopy. C₂N₁₆ can explode instantly and shows mechanical sensitivities far higher than quantitatively measurable. Nevertheless, it features interesting energetic performances, which were calculated using different quantum-chemical methods.

Novel polynitro azoxypyrazole-based energetic materials with high performance

Novel polynitro azoxypyrazole-based energetic compounds 1,2-bis (4-nitro-1H-pyrazol-5-yl) diazene 1-oxide (3) and 1,2-bis (1,4-dinitro-1H-pyrazol-3-yl) diazene 1-oxide (4) were synthesized from 5-amino-pyrazole-4-carbonitrile by optimized reactions. Their structures were characterized by elemental analysis and single-crystal X-ray diffraction techniques. Compound 3 exhibits high thermal stability (239 °C), low mechanical sensitivity (IS = 22 J, FS = 240 N) and moderate detonation performance (D_v = 8272 m s^-1, P = 28.1 GPa). Compound 4 shows moderate thermal stability (161 °C), decent mechanical sensitivity and higher detonation performance (D_v = 9228 m s^-1, P = 38.7 GPa) compared to that of RDX. These newly developed strategies for constructing novel energetic compounds enrich the content of the ever-expanding energetic materials.

Synthesis and properties of azamonocyclic energetic materials with geminal explosophores

Diversity-oriented synthesis of energetic pyrimidine structures with geminal explosophoric groups of geminal dinitro and azido-nitro groups via a novel reductive cleavage and oxidative coupling strategy is reported. Fluorine has also been introduced for the first time based on the nucleophilic coupling process. The obtained energetic pyrimidines are investigated via X-ray diffraction and theoretical techniques of electrostatic potential and proton affinity calculations. Both experimental and calculation results showed impressive detonation performances and good application prospects of the energetic pyrimidine structures. Among them, DNNC exhibited great promise as a green oxidant in solid propellant formulations to replace ammonium perchlorate (AP). TNHA (ρ = 1.79 g cm-3, D = 8537 m s-1, P = 32.69 Gpa) and TNHF (ρ = 1.85 g cm-3, D = 8517 m s-1, P = 32.64 Gpa) proved to be ideal candidates for high explosives due to their high densities and detonation properties. Moreover, TNHA could also be applied as a potential underwater explosive owing to its great heat of formation.

Modern trends in “Green” primary energetic materials

The evergrowing demand for cleaner, high-performing energetic materials (EMs) has led to a quest for replacement of currently used toxic metal-based traditional energetic compounds such as lead azide and lead styphnate.

3-R-4-(5-Methyleneazide-1,2,4-oxadiazol-3-yl)furazan and its ionic salts as low-sensitivity and high-detonation energetic materials

3-R-4-(5-Methyleneazide-1,2,4-oxadiazol-3-yl)furazan compounds as low-sensitivity and high-detonation energetic materials.

Properties and Promise of Catenated Nitrogen Systems As High-Energy-Density Materials

The properties of catenated nitrogen molecules, molecules containing internal chains of bonded nitrogen atoms, is of fundamental scientific interest in chemical structure and bonding, as nitrogen is uniquely situated in the periodic table to form kinetically stable compounds often with chemically stable N-N bonds but which are thermodynamically unstable in that the formation of stable multiply bonded N₂ is usually thermodynamically preferable. This unique placement in the periodic table makes catenated nitrogen compounds of interest for development of high-energy-density materials, including explosives for defense and construction purposes, as well as propellants for missile propulsion and for space exploration. This review, designed for a chemical audience, describes foundational subjects, methods, and metrics relevant to the energetic materials community and provides an overview of important classes of catenated nitrogen compounds ranging from theoretical investigation of hypothetical molecules to the practical application of real-world energetic materials. The review is intended to provide detailed chemical insight into the synthesis and decomposition of such materials as well as foundational knowledge of energetic science new to most chemists.

N-(2-Fluoro-2,2-dinitroethyl)azoles: a novel assembly of diverse explosophoric building blocks for energetic compound design

The first protocol forN-(dinitrofluoroethyl)ation of azoles has been created.