Energetic N-trinitroethyl-substituted mono-, di-, and triaminotetrazoles

Energetic Methylene-Bridged Furoxan-Triazole/Tetrazole Hybrids

Design and synthesis of new energetic materials retains its urgency in chemistry and materials science. Herein, rational construction and regioselective synthesis of a series of energetic compounds comprising of a methylene-bridged combination of 1,2,5-oxadiazole and nitrogen-rich azoles (1,2,4-triazole and tetrazole) enriched with additional explosophoric functionalities (nitro and azo moieties) is presented. All target materials were thoroughly characterized using IR and multinuclear NMR (1H, 13C, 14N, 15N) NMR spectroscopy, high-resolution mass spectrometry, X-ray diffraction, and differential scanning calorimetry. All synthesized energetic substances showed good thermal stability (up to 239 °C) and low mechanical sensitivity, while their performance reached or exceeded the level of TNT.

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.

Synthesis and thermal stability of a novel polyfunctional pyridine-based derivative featuring amino, nitro, and guanidine groups

A new pyridine derivative 1-(4-amino-3,5-dinitropyridin-2-yl) guanidine (ADG) was synthesized through nitration and substitution reaction using 4-amino-2-cholopyridine as raw material. Its structure was characterized by spectroscopy, nuclear magnetic resonance, and mass spectrometry. The crystal of ADG is monoclinic, space group Pbca with crystal parameters of a = 7.23 Å, b = 14.56 Å, c = 17.93 Å, α = β= γ= 90 Å, V = 1911 Å3, μ = 0.143 mm−1, and Z = 8. This new molecule exhibits moderate density ( ρ= 1.677 g cm−3), good thermal stability with a decomposition temperature of 217 °C, and moderate detonation property with detonation pressure of 20.83 GPa and detonation velocity of 7.00 km s−1. The Hirshfeld surface analysis revealed a significant contribution of weak interactions to the packing forces for molecules. Electron localization function analysis indicates that there is substantial electron localization in regions of C–H, N–H, and N–O covalent bond sites.

Imino-bridged N-rich energetic materials: C4H3N17 and their derivatives assembled from the powerful combination of four tetrazoles

Imino-bridged symmetric N-rich energetic materials with high energetics and good stability.

Recent Advances in Synthesis and Properties of Nitrated-Pyrazoles Based Energetic Compounds

Nitrated-pyrazole-based energetic compounds have attracted wide publicity in the field of energetic materials (EMs) due to their high heat of formation, high density, tailored thermal stability, and detonation performance. Many nitrated-pyrazole-based energetic compounds have been developed to meet the increasing demands of high power, low sensitivity, and eco-friendly environment, and they have good applications in explosives, propellants, and pyrotechnics. Continuous and growing efforts have been committed to promote the rapid development of nitrated-pyrazole-based EMs in the last decade, especially through large amounts of Chinese research. Some of the ultimate aims of nitrated-pyrazole-based materials are to develop potential candidates of castable explosives, explore novel insensitive high energy materials, search for low cost synthesis strategies, high efficiency, and green environmental protection, and further widen the applications of EMs. This review article aims to present the recent processes in the synthesis and physical and explosive performances of the nitrated-pyrazole-based Ems, including monopyrazoles with nitro, bispyrazoles with nitro, nitropyrazolo[4,3-c]pyrazoles, and their derivatives, and to comb the development trend of these compounds. This review intends to prompt fresh concepts for designing prominent high-performance nitropyrazole-based EMs.

The strategy for improving the stability of nitroform derivatives-high-energetic oxidant based on hexanitroethane

To develop high-energetic stability nitroform compounds, three types of nitroform derivatives based on hexanitroethane structure are designed. The guidelines for selecting these compounds are based on (1) constructing a flexible molecule and weakening the external force by elastic deformation and (2) forming negative ion or introducing electron-rich group to eliminate the electron-deficient situation. The conformations and some important properties of them are calculated at B3LYP/6-311 + G(d) level. Based on the bond order and bond dissociation enthalpy analysis, C-NO₂ bond is considered to be the most unstable position, and both of the methods can improve the stability of designed compounds. Based on molecular energy gap (HOMO-LUMO) and density of state (DOS) analysis, it is found that introducing of bridge atoms is helpful to lower the sensitivity, while the construction of anions changes both HOMO-LUMO and DOS which shows obvious ionic properties. A further study on the electrical potential surface shows that the probability for extreme values of designed compounds decreases which is beneficial for high stability. Finally, the explosive properties and impact sensitivity of them are calculated. Results show that their explosive performances are obviously better than current energetic oxidants and some of them maintain low sensitivity.

Amino-tetrazole functionalized fused triazolo-triazine and tetrazolo-triazine energetic materials

In this study, two insensitive energetic compounds using fused triazolo-triazine and tetrazolo-triazine as the framework, one amino and one tetrazole as functional groups, were prepared through a two-step reaction.

An interesting ring cleavage of a 1,2,4-oxadiazole ring

Ring-opening reaction: owing to the instability of the 1,2,4-oxadiazole ring under acidic conditions, unexpected compounds 2 and 3 were obtained. Compound 2 exhibits an oxygen balance of zero, density of 1.89 g cm⁻¹ and detonation velocity of 9307 m s⁻¹ as well as impact sensitivity of 20 J.

An interesting 1,4,2,5-dioxadiazine-furazan system: structural modification by incorporating versatile functionalities

An N-trinitroethylamino derivative and amminonium salt based on the 1,4,2,5-dioxadiazene-furazan system are synthesized and characterized. Due to their layer-by-layer structure, these two compounds show good thermal stabilities and low sensitivities.

Dancing with Energetic Nitrogen Atoms: Versatile N-Functionalization Strategies for N-Heterocyclic Frameworks in High Energy Density Materials

Nitrogen-rich heterocycles represent a unique class of energetic frameworks featuring high heats of formation and high nitrogen content, which have generated considerable research interest in the field of high energy density materials (HEDMs). Although traditional C-functionalization methodology of aromatic hydrocarbons has been fully established, studies on N-functionalization strategies of nitrogen-containing heterocycles still have great potential to be exploited by virtue of forming diverse N-X bonds (X = C, N, O, B, halogen, etc.), which are capable of regulating energy performance and the stability of the resulting energetic compounds. In this sense, versatile N-functionalization of N-heterocyclic frameworks offers a flexible strategy to meet the requirements of developing new-generation HEDMs. In this Account, the role of strategic N-functionalization in designing new energetic frameworks, including the formation of N-C, N-N, N-O, N-B and N-halogen bonds, is emphasized. In the family of N-functionalized HEDMs, energetic derivatives, by virtue of forming N-C bonds, are the most widely used type due to the good nucleophilic capacity of most heterocyclic backbones. Although introduction of carbon tends to decrease energetic performance, significant improvement in material sensitivity makes this strategy attractive for safety concerns. More importantly, most "explosophores" can be readily introduced into the N-C linkage, thus providing a promising route to various HEDMs. Formation of additional N-N bonds typically gives rise to higher heats of formation, implying the potential enhancement in detonation performance. In many cases, the increased hydrogen bonding interactions within N-N functionalized heterocycles also improve thermal stability accordingly. Introduction of a single N,N'-azo bridge into several azole moieties leads to an extended nitrogen chain, demonstrating a new strategy for designing high-nitrogen compounds. The strategy of N-O functionalization has become an increasingly efficient tool for exploring new HEDMs with both high energy and low sensitivity. As a highly dense building block, introduction of oxygen not only improves density significantly but also gives rise to a better oxygen balance. Furthermore, the N-O functionalized strategy is highly suitable for a broad variety of N-heterocycles including five-membered azoles and six-membered azines. Newly explored N-halogen and N-B functionalization strategies have endowed the resulting HEDMs with some new energetic characteristics. Typical examples include the N-halogenated fused triazole and FOX-7 as potential hypergolic oxidizers with very short ignition delay times. In addition, some exploratory studies of N-B functionalized heterocycles have expanded energetic applications as hypergolic ionic liquids, green pyrotechnic colorants, and high-oxygen carriers. Overall, flexible N-functionalization methodologies involving different N-X bond formation have not only provided an efficient approach to diverse energetic ingredients but also expanded the application scope of energetic materials. Discussion and perspectives of N-functionalized protocols are given to summarize possible structure-property correlations, thus providing efficient guidelines for future design of new HEDMs.

Oxygen-rich anion based energetic salts with high detonation performances

Novel energetic salts based on 2,2,2-trinitroethyl nitrocarbamate anion were synthesized, which exhibited promising detonation performances (detonation pressure: 29.4 to 33.1 GPa; detonation velocity: 8213 to 8596 m s⁻¹).

High performance 5-aminotetrazole-based energetic MOF and its catalytic effect on decomposition of RDX

The energetic compound [Ag₂(5-ATZ)(N₃)] (1) features a compacted 3D framework structure, remarkable thermostability above 300 °C and perfect detonation performance. Remarkably, 1 can accelerate effectively the thermal decomposition of RDX.

Energetic dinitromethyl group functionalized azofurazan and its azofurazanates

Incorporating explosophore groups such as nitro, dinitromethyl, and azo into furazan results in potential candidates for energetic materials applications.

Nitrogen-rich energetic salts of 1H,1′H-5,5′-bistetrazole-1,1′-diolate: synthesis, characterization, and thermal behaviors

A series of nitrogen-rich heterocyclic 1H,1′H-5,5′-bistetrazole-1,1′-diolate salts with excellent thermal stabilities, impact sensitivities and promising detonation performances was synthesized.

Studies on the synthesis and properties of polynitro compounds based on esteryl backbones

Four polynitro esters were derived from 2,2,2-trinitroethanol with multi-nitrobenzoic acids by transesterification.

Copper-based energetic MOFs with 3-nitro-1H-1,2,4-triazole: solvent-dependent syntheses, structures and energetic performances

Three energetic compounds assembled with 3-nitro-1H-1,2,4-triazole have exemplified that coordinated solvent molecules may have a vital effect on the detonation properties.

Nitrogen-rich salts of 1-aminotetrazol-5-one: oxygen-containing insensitive energetic materials with high thermal stability

Energetic ionic salts based on ATO exhibit a good balance between low sensitivity and high detonation performance.

N-Trinitroethyl-substituted azoxyfurazan: high detonation performance energetic materials

An N-nitrated trinitroethylamino azoxyfurazan derivative reported here possesses oxygen balance of near zero (+2.5%) and exhibits outstanding properties (Δ_fH_m, 962.1 kJ mol⁻¹; D, 9458 m s⁻¹; P, 41.2 GPa).

The nitration pattern of energetic 3,6-diamino-1,2,4,5-tetrazine derivatives containing azole functional groups

A study of nitration patterns was conducted on 3,6-diamino-1,2,4,5-tetrazines derivatives, revealing the specificity of their nitration, as well as the stability of the formed nitramines towards hydrolysis.

Versatile polyiodopyrazoles: synthesis and biocidal promise

An efficient synthetic route provides ready access to polyiodopyrazoles, including 3,4,5-triiodopyrazole; further introduction of the diiodo-methyl group increases the iodine concentration which gives rise to anti bioagent detonation products I₂ and HI, making these iodo compounds promising candidates as ingredients in agent defeat weapons (ADWs).

New thermally stable energetic materials: synthesis and characterization of guanylhydrazone substituted furoxan energetic derivatives

The synthesis and characterization of guanylhydrazone substituted furoxan energetic derivatives with good thermal stabilities and detonation performance are now reported.

3,4-Diamino-1,2,4-triazole based energetic salts: synthesis, characterization, and energetic properties

A series of energetic salts based on 3,4-diamino-1,2,4-triazole with promising detonation performances have been synthesized using a metathesis reaction method or a protonation reaction method.

Theoretical study on the tautomerization of 1,5-diaminotetrazole (DAT)

The tautomerization pathways and kinetics of 1,5-diaminotetrazole (DAT) have been investigated by means of second-order Møller-Plesset perturbation theory (MP2) and coupled-cluster theory, with single and double excitations including perturbative corrections for triple excitations (CCSD(T)). Five possible tautomers, namely 4-hydro-1-amino-5-imino-tetrazole (a), 2,5-diamino-tetrazole (b), 1,5-diamino-tetrazole (c), 2-hydro-1-imino-5-amino-tetrazole (d), and 2,4-dihydro-1,5-diimino-tetrazole (e) were identified. The structures of the reactants, transition states, and products along with the tautomerism pathways were optimized by the MP2 method using the 6-311G** basis set, and the energies were refined using CCSD(T)/6-311G**. The minimum-energy path (MEP) information for DAT was obtained at the CCSD(T)/6-311G**//MP2/6-311G** level of theory. Therein, reaction 2 (c → b) is an amino-shift reaction, while reaction 1 (c → a), reaction 3 (c → d), reaction 4 (a → e), and reaction 5 (d → e) are reactions of hydrogen-shift tautomerization. The calculated results show that 2,5-diaminotetrazole (b) with the minimum energy (taking c as a standard) among five tautomers, is the energetically preferred tautomer of DAT in the gas phase. In addition, the energy barrier of reaction 2 is 71.65 kcal · mol(-1) in the gas phase, while reaction 1 takes place more easily with an activation barrier of 61.53 kcal · mol(-1) also as compared to 63.71 kcal · mol(-1) in reaction 3. Moreover, the tautomerization of reaction 4 requires the largest energy barrier of 83.29 kcal · mol(-1), which is obviously bigger than reaction 5 with a value of 73.78 kcal · mol(-1). Thus, the hydrogen-shift of c to a is the easiest transformation, while the tautomerization of a to e is the hardest one. Again, the rate constants of tautomerization have been obtained by TST, TST/Eckart, CVT, CVT/SCT, and CVT/ZCT methods in the range 200-2500 K, and analysis indicated that variational effects are small over the whole temperature range, while tunneling effects are significant in the lower temperature range.

Theoretical studies on the structures and detonation properties of nitro derivatives of symmetric benzo-dicycloureas

The nitro derivatives of symmetric benzo-dicycloureas were designed and optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G** level. The theoretical molecular density, heat of formation, detonation velocity, and detonation pressure, estimated using Kamlet–Jacobs equations, showed that the detonation properties of compound 7 were excellent, while compounds 8 and 9 were unstable, and the molecular symmetry, steric hindrance, and hydrogen bonds were considered to be the three main factors contributing to molecular stability. These results provide basic information for the molecular design and synthesis of novel high energy density compounds.

Structure and properties of 1-amino-2-nitroguanidinium nitrate

A nitrogen-rich energetic material 1-amino-2-nitroguanidinium nitrate was fully investigated.

Synthesis and Characteristics of Energetic Materials Based on 1,2-Dinitroguanidine

A series of energetic salts based on 1,2-dinitroguanidine were successfully synthesised and fully characterised using 1H NMR, 13C NMR, and IR spectroscopy, mass spectrometry, elemental analysis, and differential scanning calorimetry. The results show that all the salts possess higher detonation properties (detonation pressures and velocities ranging from 24.8 to 30.3 GPa and 7665 to 8422 m s–1, respectively) than those of trinitrotolouene (TNT, 2,4,6-trinitromethylbenzene). The thermal stability and thermal kinetic parameters were also investigated to give a better understanding of the physical and chemical properties of these energetic salts.