PROPELLANS – PERSPECTIVE FRAME COMPOUNDS FOR THE CREATION OF HIGH-ENERGY SUBSTANCES

Гетероциклические соединения вызывают большой интерес у исследователей как потенциальные соединения в создании биологически активный веществ или веществ с высокой энергией. 3,7,10-Триоксо-2,4,6,8,9,11-гексааза[3.3.3]пропеллан (ТНАР) состоит из трех конденсированных колец, соединенных одинарной связью C1-C5 является новым, малоизученным веществом, синтезированным во втором десятилетии XXI века. Теоретические расчеты энергий нитропроизводных пропелланов с пятью или шестью атомами азота показали перспективность использования в качестве высокоэнергетических веществ. Целью работы было проведение квантово-химических расчетов теплоты образования и сгорания, а также длины пропеллановой связи нитро- и ацетилпроизводных 3,7,10-триоксо-2,4,6,8,9,11-гексааза[3.3.3]пропеллана и его восстановленного аналога 2,4,6,8,9,11-гексааза[3.3.3]пропеллана (НАР) с различным количеством заместителей. В результате исследовательской работы была выявлена следующая закономерность: последовательное введение нитрогрупп в изучаемую структуру увеличивает теплоты образования получаемых производных, тогда как для ацетильных групп тенденция противоположная. Оказалось, что гексанитропроизводное ТНАР по термодинамической стабильности сравнимо с гексанитробензолом, а восстановленный пропеллан НАР с шестью нитрогруппами сравним с CL-20. Поведение длины пропеллановой связи C1-C5 при последовательном замещении соединения ТНАР нитро- и ацетильными группами. Накопление ацетильных групп вызывает монотонное укорочение этой связи, вплоть до обычной длины C(sp3)-C(sp3). В случае нитрогрупп тенденция более сложная: сначала укорочение, а затем значительное удлинение, до 1.67 Å для шести нитрогрупп в 3,7,10-триоксо-2,4,6,8,9,11-гексанитро-2,4,6,8,9,11-гексааза[3.3.3]пропеллане. Гексаазапропеллан (НАР), несмотря на нежесткую структуру, имеет 22 стабильных конформера, тогда как у ТНАР их 2, и более короткие связи, что вероятно в дальнейшем позволит синтезировать его гексанитро производное. Heterocyclic compounds are of great interest to researchers as potential compounds in the creation of biologically active substances or substances with high energy. 3,7,10-Trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane (THAP) consists of three condensed rings connected by a single C1-C5 bond, is a new, poorly studied substance synthesized in the second decade of the 21st century. Theoretical calculations of the energies of nitro-derivatives of propellanes with five or six nitrogen atoms have shown that they are promising for use as high-energy substances. The aim of the work was to carry out quantum-chemical calculations of the heats of formation and combustion, as well as the length of the propellane bond of nitro- and acetyl derivatives of 3,7,10-trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane, as well as its reduced analogue 2,4,6,8,9,11-hexaaza[3.3.3]propellane (HAP) with a different number of substitutes. As a result of the research work, the following regularity was revealed: the successive introduction of nitro groups into the structure under study increases the heats of formation of the resulting derivatives, while the trend is opposite for acetyl groups. It turned out that the hexanitro derivative of THAP is comparable in thermodynamic stability to hexanitrobenzene, and the reduced propellane (HAP) with six nitro groups is comparable to CL-20. Behavior of the C1-C5 propellane bond length upon successive substitution of THAP compound with nitro- and acetyl groups. The accumulation of acetyl groups causes a monotonic shortening of this bond, up to the usual length of C(sp3)-C(sp3). In the case of nitro groups, the trend is more complex: first, shortening and then significant lengthening, up to 1.67 Å for six nitro groups in 3,7,10-trioxo-2,4,6,8,9,11-hexanitro-2,4,6, 8,9,11-hexaaza[3.3.3]propellane. Hexaazapropellane (HAP), despite its non-rigid structure, has 22 stable conformers, whereas THAP has two, and shorter bonds, which is likely to make it possible to synthesize its hexanitro derivative in the future.

Lower Heating Value of Jet Fuel from Hydrocarbon Class Concentration Data and Thermo-Chemical Reference Data: An Uncertainty Quantification

A detailed assessment is presented on the calculation and uncertainty of the lower heating value (net heat of combustion) of conventional and sustainable aviation fuels, from hydrocarbon class concentration measurements, reference molecular heats of formation, and the uncertainties of these reference heats of formation. Calculations using this paper’s method and estimations using ASTM D3338 are reported for 17 fuels of diverse compositions and compared against reported ASTM D4809 measurements. All the calculations made by this method and the reported ASTM D4809 measurements agree (i.e., within 95% confidence intervals). The 95% confidence interval of the lower heating value of fuel candidates that are comprised entirely of normal- and iso-alkanes is less than 0.1 MJ/kg by the method described here, while high cyclo-alkane content leads to 95% confidence bands that approach 0.2 MJ/kg. Taking a possible bias into account, the accuracy and precision of the method described in this work could be as high as 0.23 MJ/kg for some samples.

Design and Selection of Pyrazolo[3,4-d][1,2,3] Triazole-based High-energy Materials

In this study, we design a series of bridged energetic compounds based on pyrazolo[3,4-d][1, 2, 3]triazole to screen potential energetic materials with excellent detonation properties and acceptable sensitivities. The electronic structures, heats of formation, detonation velocity, detonation pressure, and impact sensitivity of the designed compounds were calculated using density functional theory. The results showed that the designed compounds have high positive heats of formation in the range of 1035.4 (A7) to 2851.4 kJ mol−1 (D2). Moreover, the designed compounds have high crystal densities and heats of detonation, which significantly enhance detonation pressures and velocities. The detonation pressures and velocities are in the ranges of 6.23 (A1) to 9.65 km s−1 (D3) and 15.7 to 43.9 GPa (E8), respectively. The impact sensitivity data also suggest that the designed compounds have impact sensitivities in an acceptable range. Considering detonation pressures, detonation velocities, and impact sensitivities, six compounds (C3, C5, D3, D5, E3, and F3) were screened as potential materials with high energy density, excellent detonation properties, and low impact sensitivities. Finally, the electronic structures of the screened compounds were simulated to provide further understanding on the physicochemical properties of these compounds.

Theoretical design of high-nitrogen energetic molecules: Performance prediction of pentazole-based derivatives

High nitrogen energetic compounds have always been a hot spot in energetic materials. In this work, we provide a new approach for the design of promising energetic molecules containing pentazole. Attractive energetic compounds include 5-amino-3-nitro-1H-1,2,4-triazole (ANTA) and 5-nitro-1,2,4-triazol-3-one(NTO) are used to effectively combine with pentazole to form a series of pentazole derivatives. Then, the NH2, NO2 or NF2 groups were introduced into the system to further adjust the property. Herein, the structures and densities of designed compounds as well as the heats of formation, detonation properties and impact sensitivities were predicted based on density functional theory (DFT). The results show that all ten designed molecules have excellent densities (1.81 g/cm3 to 1.97 g/cm3) and high heats of formation (621.66 kJ/mol to 1374.63 kJ/mol). Furthermore, detonation performances of compounds A3 (P = 41.16 GPa and D = 9.45 km/s) and A4 (P = 43.90 GPa and D = 9.69 km/s) are superior to 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and lower impact sensitivity than HMX. It exhibited that they could be taken as promising candidates of high-energy density materials. This work provides a worthy way to explore the energetic compounds with excellent performance based on pentazole.

Towards Computational Screening for New Energetic Molecules: Calculation of Heat of Formation and Determination of Bond Strengths by Local Mode Analysis

The reliable determination of gas-phase and solid-state heats of formation are important considerations in energetic materials research. Herein, the ability of PM7 to calculate the gas-phase heats of formation for CNHO-only and inorganic compounds has been critically evaluated, and for the former, comparisons drawn with isodesmic equations and atom equivalence methods. Routes to obtain solid-state heats of formation for a range of single-component molecular solids, salts, and co-crystals were also evaluated. Finally, local vibrational mode analysis has been used to calculate bond length/force constant curves for seven different chemical bonds occurring in CHNO-containing molecules, which allow for rapid identification of the weakest bond, opening up great potential to rationalise decomposition pathways. Both metrics are important tools in rationalising the design of new energetic materials through computational screening processes.