3,3'-Bi(1,2,4-oxadiazoles) featuring the fluorodinitromethyl and trinitromethyl groups.

Here we report on the preparation of two hydrogen atom free 3,3'-bi(1,2,4-oxadiazole) derivatives. 5,5'-Bis(fluorodinitromethyl)-3,3'-bi(1,2,4-oxadiazole) was synthesised by fluorination of diammonium 5,5'-bis(dinitromethanide)-3,3'-bi(1,2,4-oxadiazole). For our previously reported analogue 5,5'-bis(trinitromethyl)-3,3'-bi(1,2,4-oxadiazole), a new synthetic route starting from new 3,3'-bi(1,2,4-oxadiazolyl)-5,5'-diacetic acid was developed. In this course also hitherto unknown 5,5'-dimethyl-3,3'-bi(1,2,4-oxadiazole) was isolated. The compounds were characterised by multinuclear NMR spectroscopy, IR and Raman spectroscopy, elemental analysis as well as mass spectrometry. X-ray diffraction studies were performed and the crystal structures for the 5,5'-dimethyl and 5,5'-(fluorodinitromethyl) derivatives are reported. The energetic 5,5'-(fluorodinitromethyl) and 5,5'-(trinitromethyl) compounds do not contain any hydrogen atoms and show remarkable high densities. Furthermore, the thermal stabilities and sensitivities were determined by differential scanning calorimetry (DSC) and standardised impact and friction tests. The heats of formation were calculated by the atomisation method based on CBS-4M enthalpies. With these values and the room-temperature X-ray densities, several detonation and propulsion parameters, such as the detonation velocity and pressure as well as the specific impulse of mixtures with aluminium, were computed using the EXPLO5 code.