Combinations of furoxan and 1,2,4-oxadiazole for the generation of high performance energetic materials†
Several energetic materials, which are composed of furoxan and 1,2,4-oxadiazole backbones, were synthesized by nitrating 3,3′-bis(5-amino-1,2,4-oxadiazol-3-yl)-4,4′-azofuroxan (2) under 100 wt% HNO3 or 100 wt% HNO3/Ac2O followed by a cation metathesis. All synthesized compounds were fully characterized by multinuclear NMR spectroscopy, IR spectroscopy, and elemental analysis, while 3,3′-bis(1,2,4-oxadiazol-5(4H)-one-3-yl)-4,4′-azofuroxan (3) and diammonium 3,3′-bis(5-nitramino-1,2,4-oxadiazole-3-yl)-4,4′-azofuroxan (4a) were confirmed by single crystal X-ray diffraction. The physicochemical and energetic properties of these compounds including density, thermal stability and sensitivity were investigated. Compounds 3 and 4 have high densities (3: 1.90 g cm−3, 4: 1.92 g cm−3), which are comparable to that of HMX (1.91 g cm−3). All energetic compounds show relatively high calculated heat of formation in the range from 504.79 kJ mol−1 to 1405.62 kJ mol−1. Their detonation properties were evaluated by EXPLO5 code using the measured density and calculated heat of formation. Among them, compounds 3 and 4 have good detonation performance (3: D = 8891 m s−1, P = 34.7 GPa, 4: D = 9505 m s−1, P = 41.3 GPa) and acceptable sensitivities (3: IS = 10 J, 4: IS = 4 J), which indicate their potential applications as high-performance energetic materials.