5-Nitrotetrazol and 1,2,4-Oxadiazole Methylene-Bridged Energetic Compounds: Synthesis, Crystal Structures and Performances

A new structural type for melt cast materials was designed by linking nitrotetrazole ring with 1,2,4-oxadiazole through a N-CH2-C bridge for the first time. Three N-CH2-C linkage bridged energetic compounds, including 3-((5-nitro-2H-tetrazol-2-yl) methyl)-1,2,4-oxadiazole (NTOM), 3-((5-nitro-2H-tetrazol-2-yl)methyl)-5-(trifluoromethyl)-1,2,4 -oxadiazole (NTOF) and 3-((5-nitro-2H-tetrazol-2-yl)methyl)-5-amine-1,2,4-oxadiazole (NTOA), were designed and synthesized through a two-step reaction by using 2-(5-nitro-2H-tetrazole -2-yl)acetonitrile as the starting material. The synthesized compounds were fully characterized by NMR (1H, 13C), IR spectroscopy and elemental analysis. The single crystals of NTOM, NTOF and NTOA were successfully obtained and investigated by single-crystal X-ray diffraction. The thermal stabilities of these compounds were evaluated by DSC-TG measurements, and their apparent activation energies were calculated by Kissinger and Ozawa methods. The crystal densities of the three compounds were between 1.66 g/cm3 (NTOA) and 1.87 g/cm3 (NTOF). The impact and friction sensitivities were measured by standard BAM fall-hammer techniques, and their detonation performances were computed using the EXPLO 5 (v. 6.04) program. The detonation velocities of the three compounds are between 7271 m/s (NTOF) and 7909 m/s (NTOM). The impact sensitivities are >40 J, and the friction sensitivities are >360 N. NTOM, NTOF and NTOA are thermally stable, with decomposition points > 240 °C. The melting points of NTOM and NTOF are 82.6 °C and 71.7 °C, respectively. Hence, they possess potential to be used as melt cast materials with good thermal stabilities and better detonation performances than TNT.

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.

Epoxides of DADNE Isomers - A DFT Study

Diaminodinitroethylene (DADNE) has three constitutional isomers; cis, trans and geminal. In the present study, epoxides of these isomers are considered within the restrictions of density functional theory at the level of UB3LYP/6-31G(d,p). Certain geometrical and quantum chemical properties of them are computed. The homolytic dissociation energy for C-NO2 bond in each case has been calculated at the level of UB3LYP/6-311++G(d,p). Based on the calculations performed, certain predictions are made for the impact sensitivities and specific impulse values of these epoxide derivatives of DADNE isomers.

Synthesis, characterization and properties of a novel energetic ionic salt: dicarbohydrazide bis[3-(5-nitroimino-1,2,4-triazole)]

DCBNT, a new compound, exhibits low friction and impact sensitivities, good thermal stability, and promising detonation pressure and detonation velocity.