A series of six isomers was synthesized with three nitro groups at various positions on the 3,5-di(pyrazolyl)-1,2,4-oxadiazole framework, providing a representative set for evaluating the effects of positional isomerism on physicochemical properties and performance. These isomers were thoroughly characterized by spectral data. X-ray crystallographic analysis of two isomers was also performed. The physicochemical properties of the isomers, such as density, thermal behavior, enthalpy of formation, and sensitivity towards impact and friction, were compared. The detonation properties were evaluated using the PILEM code. Based on physiochemical properties (density, thermal stability, and sensitivity) and the calculated detonation properties, compound 8 was found to have the best performance among the energetic isomers of this study.

Crystal structure and associated local mechanical properties are considered to be among the factors determining the impact sensitivity of reactive chemicals. However, their contribution can hardly be separated from those stemming from the molecular structure per se (number and presence of explosophores, energy content). In this work, we analyzed a set of structurally diverse energetic compounds to look for possible correlations among the level of response toward impact stimulation (sensitivity), local mechanical properties, and crystal structure. In line with previous literature, a strong correlation with the energy content and impact sensitivity emerges, but the target safety property is also affected by the average elastic modulus of the crystal. Since the mechanical properties of crystalline materials are largely determined by the crystal structure, we investigate the rigidity and anisotropy of intermolecular interactions. We find that an increase in the anisotropy of the intermolecular interactions' network leads to a decrease in impact sensitivity. Our findings on the mechanical properties within a diverse data set of explosives and their correlations with the safety of materials might be used for prediction models and controlled design of future materials.

N-(Het)arylation of isomeric dinitropyrazoles bearing amino group at nitrogen of the ring have been investigated. Isomeric N-(picrylamino)- and N-[(N’-methyl)dinitropyrazolylamino) derivatives were synthesized. These isomers were characterized with respect to their spectral properties and energetic performance. X-ray crystallographic analyses for isomers were also performed. The structure-property relationships for isomers have been analyzed. 3,4-Dinitro-1-(2,4,6-trinitrophenylamino)-1H-pyrazole (2b) was found to have the best performance among the energetic isomers of this study.

Early detection of the thermal and explosion hazards of chemicals is vital for safe handling and manufacturing. While thermal analysis methods using sealed-cell differential scanning calorimetry are commonly used to screen for shock sensitivity via empirical Yoshida-type equations, the reliability of the underlying thermal data and the robustness of this predictive approach require systematic validation. This study investigates the Yoshida approach from thermal analysis and energetic materials perspectives. We compiled a data set of more than 100 reactive compounds, including common reagents and energetic materials, to critically evaluate the variability of decomposition enthalpy and characteristic onset by DSC. Our results reveal significant scatter, up to several times, in reported decomposition heat values, attributable to factors such as gas leakage, calibration inconsistencies, interactions with crucible, and thermal runaway. We establish a correlation between decomposition enthalpy and the thermodynamically estimated maximal heat of explosion for the compound. Furthermore, by comparing original Yoshida and Pfizer-modified equations against experimental mechanical sensitivity data, we demonstrate that the conservative Pfizer adaptation achieves a superior recall (true positive rate) for identifying hazardous compounds. This work underscores the thermodynamic (energy content) and kinetic (onset temperature) foundations of the Yoshida-type equations, highlights the critical need for standardized, high-quality thermal data, and provides practical guidance for enhancing the reliability of early-stage hazard screening tools in chemical research and development.

Energetic materials are essential substances for the development of advanced aerospace technologies and welding applications. In this study, we synthesized new high-nitrogen energetic salts based on linearly linked 1,2,4-triazole, furoxan and N-hydroxytetrazole scaffolds. All the prepared substances were thoroughly characterized using multinuclear NMR spectroscopy, IR spectroscopy and X-ray diffraction analysis. The synthesized energetic compounds exhibited a wide range of thermal stability, ranging from moderately stable guanidinium-based salts (Td: 153-173 degrees C) to highly stable sodium and [1,2,4]triazolo[4,3-b][1,2,4]triazolium salts, respectively (Td: 227-236 degrees C). All synthesized energetic materials had high enthalpies of formation (362-1074 kJ mol-1) resulting in good detonation performance (D: 6.9-8.3 km s-1; P: 19-32 GPa) simultaneously retaining friction insensitivity. Overall, the proposed method for the assembly of triheterocyclic substances offers a promising avenue for the development of nitrogen-rich energetic materials.

Melting often accompanies the thermolysis of crystalline organic compounds and brings additional complexity for the thermokinetic analysis of the decomposition process. As a consequence of this, the kinetic data for the thermolysis of particular compounds both in the solid- and liquid-state are rarely reported and often contradict each other. Herein, we proposed a strategy of dealing with the melting with decomposition case for various types of thermoanalytical experiments (DSC and TGA) and temperature programs (both isothermal and non-isothermal). Furthermore, we proposed to study several related species differing by non-energetic moieties to shift the melting point over a wide temperature range without remarkable changes in the decomposition temperatures. To illustrate the value of the proposed approach, we consider the decomposition kinetics of the three halogenated benzene derivatives bearing a 2-nitrodiazene-1-N-oxide moiety. In all cases, the nonisothermal experimental data are fitted by a first-order reaction paralleled by the autocatalytic process. The isothermal experiments below the melting point of compounds in ramped heating runs still show the formation of liquid. This observation and other findings are explained using the Bawn kinetic model. The activation energies for the liquid-state decomposition of all compounds were found to be 145 ± 3 kJ mol-1. The experiment was complemented by the highly accurate CCSD(T)-F12 quantum chemical calculations. Theory predicts the primary decomposition pathway to be the radical scission of a nitro radical followed by the fast elimination of nitrous oxide. With the suggested approach, we determined the acceleration factor of the rate constant when decomposition commences in the solid or liquid state to be 2-4 times, not orders of magnitude, as was proposed in some previous publications.

Five novel peroxosolvates of 3,4,5-trinitropyrazole salts (KTNP center dot H2O2, KTNP center dot 0.9(H2O2)center dot 0.1(H2O), CsTNP center dot 0.5 (H2O2), CsTNP center dot H2O2, and GuaTNP center dot H2O2) were reported. Crystal structures of obtained adducts (and their starting salts) were determined. In peroxide adducts, metal atoms exhibit irregular coordination polyhedra with CN numbers ranging from 10 to 12 and are bonded with two or three H2O2 ligands. All obtained hydrogen peroxide adducts are stabilized by hydrogen bonding networks between peroxide molecules and organic anions. Potassium derivative KTNP center dot H2O2 is readily obtained from dilute peroxide solutions and shows high thermal stability for peroxide adducts and acceptable impact and friction sensitivities. Periodic DFT calculations show that high stability is a consequence of the significantly higher lattice energy for peroxosolvate than for the unsolvated salt or hydrate.

Polynitro glycoluril derivatives, viz., 1,4-dinitroglycoluril (DINGU) and 1,3,4,6-tetranitroglycoluril (sorguyl, TNGU), are very promising components of energetic formulations because of their good detonation performance, high density, and low sensitivity to mechanical stimuli. However, the data available on the kinetics and mechanism of their thermal decomposition remain very limited. In the present contribution, we employed mutually complementing advanced experimental techniques (DSC and TGA in the solid state both under linear heating and isothermal conditions along with advanced thermokinetic models, optical microscopy, and gas product detection) and predictive quantum chemical calculations (DLPNO-CCSD(T)) to study the thermal stability of the title species. The experimental thermolysis data of DINGU and TNGU including both gravimetric (TGA) and caloric (DSC) datasets were used for building two-step kinetic models that universally describe all DSC and TGA data. More specifically, the first step for both nitroglycolurils is a nucleation-growth reaction described by the Kolmogorov-Johnson-Mehl-Avrami-Erofeev equation (KJMAE), while the second consecutive step obeys flexible Prout-Tompkins and third-order reaction models for DINGU and TNGU, respectively. The experimental findings were complemented by the mechanistic details from DLPNO-CCSD(T) quantum chemical calculations. The radical N-NO2 bond cleavage is the dominant primary decomposition channel with the kinetic parameters Ea = 185.8 kJ mol-1 and log(A/s-1) = 18.6 for DINGU, and Ea = 166.1 kJ mol-1 and log(A/s-1) = 18.7 for TNGU, respectively. Apart from the primary reactions, we also considered a number of uni- and bimolecular secondary decomposition channels. We found that the "bridge" C-C bond unzipping followed by the ˙NO2 radical elimination with activation barriers of ∼120-130 kJ mol-1 are the most energetically favorable unimolecular secondary channels. At the same time, the hydrogen abstraction from an initial reagent molecule by a primary nitramine radical product is the most important bimolecular secondary channel. The reaction mechanism switches from bimolecular to unimolecular C-C bond unzipping at the isokinetic temperatures of 860 K for DINGU and 610 K for TNGU. The reported secondary reactions might also be important in the thermolysis mechanisms of the related energetic secondary nitramines (e.g., RDX, HMX, and CL-20). Apart from this, we also determined a mutually consistent set of thermochemical and phase change data for a series of polynitro glycoluril derivatives.

A direct synthetic route to an assembly of new energetic materials composed of two 1,2,5-oxadiazole 2-oxide (furoxan) rings connected via an azoxy linker and coupled with a 4-nitramino-3,5-dinitrophenyl scaffold was realized. Due to an advanced installation of azoxy and nitramino moieties, synthesized materials showed good densities (1.65-1.74 g cm-3) and an increased oxygen balance. Advantageously, all prepared energetic substances demonstrated good detonation velocities (7.3-7.8 km s-1) and retained acceptable sensitivity to impact, thus elucidating new directions in the construction of balanced high-energy materials.

Isomeric high-energy oxygen- and nitrogen-rich compounds are an attractive and increasingly important family of energetic molecular materials. The introduction of isomerism as a methodology into the practice of designing energetic compounds is not only of fundamental importance, but also expands the possibilities for practical applications. The three explosophoric isomeric N2O2CH3 groups, N-methylnitramide (isomer type A), 1-methoxydiazene 1-oxide (isomer type B), and 2-methoxydiazene 1-oxide (isomer type C), have been demonstrated and are promising building blocks for molecular engineering, providing tuning of properties important for energetic materials, such as density, enthalpy of formation, and sensitivity to external stimuli. Diverse combinations of the above isomeric groups with furazan-based frameworks were synthesized, which led to various molecular architectures that provided an opportunity to consider some structure-properties relationships. The spectral, structural and thermochemical characteristics, as well as impact/friction sensitivities and detonation performance of isomeric analogues illustrate the extent to which explosophoric group isomerism can be used to tune the properties of energetic molecules.

The necessity of novel improved ingredients for peculiar applications like powders and propellants is boosting the research of energetic materials to replace conventional components. This work deals with the design, synthesis and complete characterization of novel energetic furazans 1a–e containing little-studied explosophoric 5-azido-1,3-dinitro-1,3-diazapentyl moiety[–N(NO2)CH2N(NO2)CH2CH2N3]. The simple and concise method for the synthesis of these compounds has been developed on the basis of easily available aminofurazan derivatives. The compounds obtained have good thermal stability (onset decomposition temperatures 115–157 °C), high enthalpies of formation (1459–1914 kJ⋅kg−1) and acceptable densities (1.64–1.73 g⋅cm−3). In terms of detonation performance, all synthesized compounds (detonation velocities D = 8.1–8.3 km⋅s−1, detonation pressures PC–J = 28–31 GPa) are comparable with pentaerythritol tetranitrate (PETN) (D = 8.3 km⋅s−1, PC–J = 31 GPa). Compounds 1a, 1d and 1e, comprising two 5-azido-1,3-dinitro-1,3-diazapentyl units and furazan backbones, due to its physicochemical, energetic and operational properties, are prototypes of an effective energetic filler for future high-performance propellants and powders.

The design and synthesis of advanced energetic non-hydrogen 1,2,5-oxadiazole assemblies were realized. All target azo-1,2,5-oxadiazole assemblies have high densities (1.89-1.90 g cm-3), good thermal stabilities (180-181 °C), high enthalpies of formation (933-955 kJ mol-1), and positive oxygen balance with respect to CO (+7.5%). As a result, these compounds exhibit high detonation velocities (9.0 km s-1), high detonation pressures (38 GPa), and excellent heats of detonation (5.82-5.85 kJ g-1), unveiling new opportunities in the search for next-generation functional organic materials.

A set of novel biheterocyclic energetic materials incorporating the 4-nitroisoxazole scaffold was synthesized. Thus, prepared species demonstrated excellent thermal stability (181-244 °C), good densities (1.71-1.74 g·cm-3), and detonation velocities (7.6-8.3 km s-1), while retaining insensitivity to friction. To the best of our knowledge, this is the first example of an incorporation of the 4-nitroisoxazole scaffold into the structure of high-energy materials.

Nitration of 6-R-4-phenylpyrazolo[3,4-d][1,2,3]triazoles at the phenyl substituent is accompanied by the triazole ring opening to give new 3-R-4-diazo-1-(di)nitrophenylpyrazole-5-nitrimines. Chemical and physicochemical properties of the prepared compounds are reported.

This paper provides the first in-depth study of energetic methoxy-NNO-azoxy compounds. 3-Amino-4-(methoxyNNO-azoxy)furazan (7) is a useful precursor to a number of high-enthalpy substituted (methoxy-NNO-azoxy) furazans enriched with explosophoric functionalities (azofurazan 8, nitrofurazan 9, azoxyfurazan 10 and methylene dinitramine 11). It was shown for the first time that the interaction of nitroso compounds with salts of O-substituted N-nitrohydroxylamines leads to the formation of corresponding azoxy-oxy [N(O)=N-O] compounds, as exemplified by the reaction of 3-amino-4-nitrosofurazan (15) with the ammonium salt of O-methyl-Nnitrohydroxylamine (16) to give 3-amino-4-(methoxy-NNO-azoxy)furazan (7). This novel approach turned out to be the most suitable for the multigram synthesis of aminofurazan 7. The resulting (methoxy-NNO-azoxy)furazans 7-11 have good thermal stability (onset decomposition temperatures 148-238 degrees C), high experimental enthalpies of formation (1435-2750 kJ & sdot;kg- 1) and acceptable densities (1.57-1.75 g & sdot;cm- 3). In terms of detonation performance, all synthesized compounds (detonation velocities D = 7.9-8.5 km & sdot;s- 1, detonation pressures PC-J = 26-32 GPa) lie between 1,3,5-trinitro-1,3,5-triazinane (RDX) (D = 8.9 km & sdot;s- 1, PC-J = 36 GPa) and N-methyl-N-(2,4,6trinitrophenyl)nitramide (Tetryl) (D = 7.6 km & sdot;s- 1, PC-J = 26 GPa). The sensitivity study was performed and the results were compared to those for prevalent energetic materials. We have shown the extent to which introduction of the methoxy-NNO-azoxy group into a molecule can be used to tune the crucial properties of energetic materials (enthalpy of formation and thermal stability).

The synthesis verification of 3-amino-4-azido-1,2,5-oxadiazole and its structural characterization by IR, NMR spectroscopy, X-ray diffraction, and elemental analysis have been carried out. Its thermal behavior (TG-DSC), standard enthalpy of formation, sensitivity to mechanical stimuli, and detonation parameters have been studied. Our study has revealed the broad prospects of 3-amino-4-azidofurazan application as a precursor to novel energetic materials.

The reaction of 1-chloromethoxy-3,3-dimethyltriaz-1-ene 2-oxide with dinitropyrazoles produced the corresponding dinitropyrazolylmethyl-containing diazenium-1,2-diolates, 1-[(dinitro-1H-pyrazol-1-yl)methoxy)]-3,3-dimethyltriaz-1-ene 2-oxides. The obtained compounds were characterized by 1H, 13C, and 14N NMR spectroscopy. The synthesized 3,4- and 3,5-dinitro derivatives were studied by X-ray diffraction. The densities and the decomposition onset temperatures of the new compounds were experimentally determined and their detonation parameters were calculated.

Nitrogen heterocyclic scaffolds retain their leading position as valuable building blocks in material science, particularly for the design of small-molecule energetic materials. However, the search for more balanced combinations of directly linked heterocyclic cores is far from being exhausted and aims to reach ideally balanced high-energy substances. Herein, we present the synthetic route to novel pyrazole-furoxan framework enriched with nitro groups and demonstrate a promising set of properties, viz., good thermal stability, acceptable mechanical sensitivity, and high detonation performance. In-depth crystal analysis showed that the isomers having lower-impact sensitivity values in both types of regioisomeric pairs are those with the exocyclic furoxan oxygen atom being closer to the pyrazole ring. Owing to the favorable combination of high crystal densities (1.83-1.93 g cm(-3)), positive oxygen balance to CO (up to +13.9%), and high enthalpies of formation (322-435 kJ mol(-1)), the synthesized compounds show high calculated detonation velocities (8.4-9.1 km s(-1)) and excellent metal accelerating abilities. The incorporation of the 3-nitrofuroxan moiety increases the thermal stability (by ca. 20 degrees C) and decreases the mechanical sensitivity of target hybrid materials in both types of regioisomeric pairs. Simultaneously, the detonation performance of 3-nitrofuroxans is almost identical to that of 4-nitrofuroxans, highlighting the potential of the regioisomeric tunability in the future design of energetic materials.

Novel energetic materials (EM) often combine two intrinsically counter trends, viz., a high energy density and mediocre safety parameters, like thermal stability and sensitivity toward mechanical stimuli. A rational design of promising EMs requires a proper understanding of their thermal stability at both macroscopic and molecular levels. In the present contribution, we studied in detail the thermal stability of 4,4 '-dinitro-3,3 '-diazenofuroxan (DDF), an ultrahigh-performance energetic material with a reliable experimental detonation velocity being very close to 10 km s-1. To this end, we employed a set of complementary thermoanalytical (DSC and TGA in the solid state along with advanced thermokinetic models, optical microscopy, and gas products detection) and theoretical techniques (DLPNO-CCSD(T) quantum chemical calculations). According to the DSC measurements, the solid-state thermolysis of DDF turned out to be a complex three-step process. The decomposition commences at similar to 85 degrees C and the most intense heat release occurs at similar to 130 degrees C depending on the heating rate. In order to properly describe the kinetics of DDF thermolysis beyond the simple Kissinger and Friedman methods, we applied a "top-down" kinetic approach resulting in the formal model comprised of three independent stages. A flexible Kolmogorov-Johnson-Mehl-Avrami-Erofeev equation was applied for the first decomposition stage along with the extended Prout-Tompkins equation for the second and third processes, respectively. The formal exponent in the former equation turned out to be close to a second order, thus suggesting a two-dimensional nuclei-growth model for the first stage. We rationalized this fact with the aid of optical microscopy experiments tracking the changes in the morphology of a solid DDF sample. Then, we complemented the formal macroscopic kinetics with some mechanistic patterns of the primary decomposition channels from quantum chemical calculations. The three reactions involving all important moieties of the DDF molecule turned out to compete very closely: viz., the nitro-nitrite isomerization, radical C(heterocycle)-N(bridge) bond scission and molecular decomposition comprised of the consequent N-O and C-C bond scissions in a furoxane ring. The DLPNO-CCSD(T) activation barriers of all these reactions were close to similar to 230 kJ mol-1. Most importantly, the calculations provide some mechanistic details missing in thermoanalytical experiment and formal kinetic models. Apart from this, we also determined a mutually consistent set of thermochemical and phase change data for DDF.