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.

The synthesis of novel energetic compounds for the development of propellants and powders with significantly improved characteristics is an important and complex task. The combination of little- studied hydrogen-containing explosophoric groups and high nitrogen heterocycles is a powerful strategy for creating the compounds needed to address this challenge. A number of energetic substituted furazans, bearing a rare 1,3-dinitro-1,3-diazabutyl group, were synthesized and their properties were thoroughly studied. The resulting (1,3-dinitro-1,3-diazabutyl)furazans 1b–f have good thermal stability (onset decomposition temperatures 124–160 °C), high experimental enthalpies of formation (947–1528 kJ/kg) and acceptable densities (1.60–1.70 g/cm3). In terms of detonation performance, all synthesized compounds (detonation velocities D = 8.0–8.3 km/s, detonation pressures PC–J = 27–30 GPa) are comparable with pentaerythritol tetranitrate (PETN) (D = 8.3 km/s, PC–J = 31 GPa). For novel compounds "structure-property" relationships have been revealed that will allow predicting the key energetic characteristics of hypothetical compounds containing 1,3-dinitro-1,3-diazabutyl explosophoric group.

Fused nitrogen heterocycles emerged recently as promising scaffolds for the design of small-molecule energetic materials. Herein, we present the synthetic route to a series of new furazano[3,4-e][1,2,4]triazolo[4,3-a]pyrazines demonstrating outstanding thermal stability (the decomposition onset above 300 °C) and low mechanical sensitivity. Moreover, a favorable combination of high crystal densities (1.68-1.84 g cm-3) and high enthalpies of formation (240-960 kJ mol-1) results in decent detonation parameters of the synthesized compounds (7.1-8.5 km s-1) unveiling new prospects in smart materials design.

A set of new energetic materials composed of 1,2,5-oxadiazole moieties coupled with the 4-amino-3,5-dinitrophenyl scaffold through the 1,2,4-oxadiazole linker was designed and synthesized. Synthesized energetic substances exhibit high densities (1.66-1.74 g cm-3), positive enthalpies of formation (17-572 kJ mol-1), and high combined nitrogen-oxygen content (61-67%). Advantageously, newly prepared materials showed high thermal stability (up to 251 °C) and complete insensitivity to friction while retaining good detonation velocities (6.9-7.2 km s-1). Overall, fine modulation of oxadiazole and nitroaromatic scaffolds represents a good strategy for an assembly of balanced and heat-resistant energetic materials.

Pyrazine 1,4-dioxide (PZDO) is a chemical frequently employed as a coformer in cocrystal design. It has two N-oxide fragments that signify potential hazards, but we found no information about it in prior literature. Therefore, we investigate the thermal behavior, thermochemical properties, and mechanical sensitivity of the title compound. We demonstrate that the material explodes in standard impact tests at a certain drop energy. By the level of its computed energetic potential, PZDO approaches benchmark trinitrotoluene. We screened ten energetic materials for cocrystal formation with PZDO using thermal analysis methods and predicted three novel cocrystals. However, we failed to grow the X-ray quality crystals by the conventional approach due to significantly differing solubility of PZDO and other components in common solvents. Two suitable coarse cocrystals of 3,4-dinitropyrazole/PZDO and 3,5-dinitropyrazole/PZDO were finally prepared by resublimation (vacuum recondensation of preformed comelt), and its X-ray structure is reported. Overall, we characterize PZDO as an energetic material and highlight the potential risks associated with the compound. The preparation of cocrystals via the gas phase route, although laborious, may be effective when the traditional (via solution) approach fails.

The evolution of energetic materials science presents new challenging tasks associated with the creation of advanced technologies for sustainable development of the future. In this work, a set of new heat-resistant high-energy materials incorporating the polynitrophenyl-1,2,5-oxadiazole scaffold enriched with azo/azoxy moieties have been designed and synthesized. Due to a smart combination of explosophoric groups and 1,2,5-oxadiazole rings, the prepared high-energy substances have excellent thermal stability (up to 300 degrees C), good densities (up to 1.75 g cm-3), high enthalpies of formation (340-538 kJ mol-1), and high combined nitrogen-oxygen content (63-68%). In-depth structural analysis revealed the presence of strong intra- and intermolecular hydrogen bonds in aminodinitrophenyl derivatives, which in combination with the small deviation of electrostatic potential values explains the low mechanical sensitivity of these materials. At the same time, trinitrophenyl-1,2,5-oxadiazoles incorporating three adjacent non-coplanar nitro groups demonstrated higher sensitivity to impact, albeit retaining complete insensitivity to friction. The overall performance of the thus prepared high-energy substances exceeds that of the known heat-resistant explosive hexanitrostilbene. Therefore, the newly synthesized family of energetic polynitrophenyl-1,2,5-oxadiazoles provides a fruitful foundation for the creation of the advanced heat-resistant energetic materials of the future.

New promising energetic materials comprised of 1,2,4-triazole and furoxan rings and bearing explosophoric nitro group were rationally designed and synthesized. All newly prepared compounds were thoroughly characterized and their physicochemical properties were estimated. In the newly synthesized series, (1,2,4-triazolyl)furoxan 4 is completely insensitive to impact and friction and possesses good detonation performance (D = 8.4 km s-1; P = 33 GPa) enabling its further exploration as a promising high-energy material. New energetic (1,2,4-triazolyl)furoxans were synthesized and their physicochemical properties were estimated. The obtained results serve as an evidence that an alliance of 1,2,4-triazole and furoxan rings may constitute a suitable platform for the construction of promising energetic materials. image

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Mechanical stress is an important trigger of reactions in chemicals. Historically, the standard testing protocols for impact and friction sensitivity have been developed mainly for energetic materials and explosives. As a result, the structure-mechanical safety data is available for common explosives and is constantly reported for newly synthesized energetic compounds. The present work is motivated by the widely held among practitioners idea of high variability of mechanical sensitivity data, the advancements of new heterocyclic and high-nitrogen chemistry, and clear need in benchmark reference data set for QSPR modeling. We started from literature analysis and have already noted that many chemical papers lack the details required to replicate their findings regarding mechanical sensitivity. Next, we prepared over 100 species that have been previously synthesized and whose sensitivity had been reported by other researchers. The scatter within the literature and present study's results is illustrated and analyzed. Finally, we proposed a data set of 83 chemicals, which have the most reliable mechanical sensitivity data. This benchmark data set is recommended to be used for modeling of mechanical hazards of reactive chemicals. The logics of how this data set can be expanded in future is given; it might involve the collaborative efforts by different groups.

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.

The preparation of multipurpose high-energy materials for space technologies remains a challenging task and such materials usually require special precautions and fine tunability of their functional properties. To unveil new opportunities en route to high-performance energetic materials, novel potential melt-castable explosives and energetic plasticizers incorporating a (1,2,3-triazolyl)furazan scaffold enriched with nitro and nitratomethyl explosophoric functionalities were synthesized. The successful implementation of the regiodivergent approach enabled the preparation of regioisomeric (nitratomethyltriazolyl)furazans that possessed significantly different physicochemical properties classifying the target materials as melt-castable substances or energetic plasticizers. Hirshfeld surface calculations supported by energy framework plots were also performed to better understand the relationship between the molecular structure and sensitivity. All the prepared (1,2,3-triazolyl)furazans show high nitrogen-oxygen contents (76-77%), good experimental densities (up to 1.72 g cm-3) and high positive enthalpies of formation (180-318 kJ mol-1) resulting in good detonation performances (D = 7.1-8.0 km s-1; P = 21-29 GPa). Overall, this work unveils novel strategies for the construction of balanced energetic melt-castable substances or plasticizers for various applications.

Известно, что чувствительность к удару не является исключительно внутренним свойством соединения, а зависит от множества факторов, определяемых химическими и физическими свойствами образца, а также типом прибора и условиями измерения. Поэтому сравнение данных по чувствитель- ности, полученных на различных приборах и по разным методикам, затруднено. Более того, даже при использовании однотипных приборов, но разными лабораториями расхождения могут быть суще- ственными. Основываясь на исследованиях, выполненных почти 90 лет назад, в работе предложена относительно простая, но универсальная методика с использованием копра типа BAM (Bundesanstalt fur Materialforschung), модифицированного для измерения скорости падения и отскока груза. Комбинируя результаты холостых опытов и опытов с образцом энергетического материала (ЭМ) получены абсолютные значения величины энергии, передаваемой образцу и поглощаемой им при энергии удара, соответству- ющей порогу инициирования. Получаемый во время испытаний энергетический баланс показывает важность своевременного технического обслуживания прибора, так как величина энергии, поглоща- емая испытательным прибором, имеющим даже незначительные механические поломки, может сильно возрасти по сравнению с исправным состоянием. Предлагаемая методика позволяет оценить разницу между полной энергией груза, принимаемой в качестве характеристики чувствительности, и реальными значениями энергии, переданной образцу при ударе и поглощенной образцом. Сделан вывод о том, что полученные значения энергии, поглощенной образцом на пороге инициирования, являются более реле- вантными характеристиками материалов, чем величина полной энергии груза, соответствующая 50%-ной вероятности инициирования реакции в образце.

A number of new high-performing energetic materials possess explosophoric functionalities, high nitrogen content, and fused heterocyclic blocks. Two representatives of these materials have been synthesized recently, namely, 1,2,9,10-tetranitrodipyrazolo[1,5-d:5',1'-f][1,2,3,4]-tetrazine (1) and 2,9-dinitrobis([1,2,4]triazolo)[1,5-d:5',1'-f][1,2,3,4]tetrazine (2). The thermal stability of these energetic materials bearing the N-N-N = N-N-N fragment and three closely related compounds has been investigated for the first time. The thermal decomposition process of analyzed compounds was complicated by the appearance of the liquid phase, sublimation of the material, and autocatalysis by reaction products. In contrast to the traditional approach to the kinetic modeling based on data from either TGA or DSC, we use both signals' data measured at the same time and perform the joint kinetic analysis using the model-fitting technique to obtain the pertinent kinetic description of the process. Of the analyzed materials, 1 and 2 show the lowest thermal stability in melt with a characteristic rate constant of 2.6 × 10-3 s-1 at 250 °C. The kinetic parameters and calculated detonation performance data were used in the model to describe the mechanical sensitivity. The model output and the experimental friction sensitivity data show a respectable agreement, but more data are required to draw firm conclusions. In general, the provided thermal stability and kinetic data can be used for thermal response and storage modeling of these new N6-type energetic materials. The developed thermokinetic approach, joint model-fitting of several thermal analysis signals, can be applied to other complex thermally induced processes to increase the value and credibility of the kinetic findings.

Impact sensitivity of energetic material is considered to be not an intrinsic property of the compound, but to depend on multiple variables, including, in addition to chemical nature of the substance, both the powder and the instrument-depending factors. Therefore, the comparison of the sensitivity data obtained using different impact machines and measurement protocols, and even by the same ones but in the different laboratories is difficult. Based on the works carried out almost 90 years ago, we propose a relatively simple but versatile technique using the modified standard fallhammer to measure the drop weight speed in downward and upward directions. The combination of the tests without sample and with sample of energetic material (both for the "triggered" and "not-triggered" cases) allows obtaining the energy transferred to and absorbed by the sample at the weight-height load, corresponding to the reaction threshold. An energy balance during the impact event is calculated to show the importance and the maintenance-dependency of the energy losses stored in test machine, and to illustrate the difference between the full energy value and the actual energy absorbed by the sample. One of the outputs of the suggested procedure are the values of energy absorbed by the sample at reaction threshold. These values are obtained in the course of standard testing protocol, in addition to the nominal drop energy value, corresponding to 50% probability of the reaction initiation. The suggested "real" energy values represent more relevant measure of mechanical hazard than usually reported nominal drop energy values.

A number of new energetic compounds were synthesized based on a combination of pyrazole, furazan, and 1,2,4-oxadiazole. Density, temperature of decomposition, and mechanical sensitivity of the compounds obtained were experimentally determined. Their detonation parameters were calculated.

A convenient method to access the above perchlorates has been developed, based on the cyclocondensation of 3-aminofurazans with 1,3-diketones in the presence of HClO4. All compounds were fully characterized by multinuclear NMR spectroscopy and X-ray crystal structure determinations. Initial safety testing (impact and friction sensitivity) and thermal stability measurements (DSC/DTA) were also carried out. Energetic performance was calculated by using the PILEM code based on calculated enthalpies of formation and experimental densities at r.t. These salts exhibit excellent burn rates and combustion behavior and are promising ingredients for energetic materials.

For the first time, complex geometry combustible structures of an ammonium perchlorate–polylactic acid composite have been successfully printed using fused deposition modeling (FDM). The structural and energetic capabilities of the printed structures are demonstrated. Combined with the ability to be produced by FDM printing, these combustible elements could afford many practical applications.

A reliable kinetic description of the thermal stability of energetic materials (EM) is very important for safety and storage-related problems. Among other pertinent issues, autocatalysis very often complicates the decomposition kinetics of EM. In the present study, the kinetics and decomposition mechanism of a promising energetic compound, 5-amino-3,4-dinitro-1H-pyrazole (5-ADP) were studied using a set of complementary experimental (e.g., differential scanning calorimetry in the solid state, melt, and solution along with advanced thermokinetic models, accelerating rate calorimetry, and evolved gas analysis) and theoretical techniques (CCSD(T)-F12 and DLPNO-CCSD(T) predictive quantum chemical calculations). The experimental study revealed that the strong acceleration of the decomposition rate of 5-ADP is caused by two factors: the progressive liquefaction of the sample directly observed using in situ optical microscopy, and the autocatalysis by reaction products. For the first time, the processing of the non-isothermal data was performed with a formal Manelis-Dubovitsky kinetic model that accounts for both factors. With the aid of quantum chemical calculations, we have rationalized the autocatalysis present in the formal kinetic models at the molecular level. Theory revealed an unusual primary decomposition channel of 5-ADP, viz., the two subsequent sigmatropic H-shifts in the pyrazole ring followed by the C-NO2 bond scission yielding a pyrazolyl and nitrogen dioxide radicals as simple primary products. Moreover, we found the secondary reactions of the latter radical with the 5-ADP to be kinetically unimportant. On the contrary, the substituted pyrazolyl radical turned out to undergo a facile addition to 5-ADP, followed by a fast exothermic elimination of another ˙NO2 species. We believe the latter process to contribute remarkably to the observed autocatalytic behavior of 5-ADP. Most importantly, the calculations provide detailed mechanistic evidence complementing the thermoanalytical experiment and formal kinetic models.

A series of novel, structurally diverse 1,2,4- and 1,2,5-oxadi- azole assemblies was synthesized from readily available furoxanyl precursors. Experimentally determined physico-chemical properties and calculated detonation parameters showed an application potential of the prepared nitrogen-oxygen molecular systems as promising energetic materials.