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.

Chemistry and structures of hexakis(halogenomethyl)-, hexakis(azidomethyl)-, and hexakis(nitratomethyl)disiloxanes.

An investigation of the structures and chemistry of substituted hexamethyl disiloxanes ((XCH2)3Si)2O; X=F, Cl, Br, I, N3 , and ONO2) is reported. New synthetic routes to the precursor hexakis(chloromethyl)disiloxane are presented. The products with X=Cl, Br, I, and N3 were characterized by NMR, IR, and Raman spectroscopy. In addition, the single-crystal structures of the products with X=Cl, Br, and I are discussed in detail. The compounds with X=F and ONO2 were not obtained in their pure form; instead investigations of the decomposition products revealed their conversion into intermediates. Theoretical calculations of the gas-phase structures at the B3LYP/cc-pVDZ, B3LYP/3-21G, MP2/6-31G*, and MP2/3-21G levels of theory are used to explain the chemical and physical behavior of the compounds with X=Cl, Br, I, N3, and ONO2. A new decomposition pathway of hexakis(nitratomethyl)disiloxane is presented and is used to explain their remarkable instability. The energetic properties and values of the nitrate and azide derivatives were calculated at the CBS-4M level of theory by using the improved EXPLO5 computer code version 6.01.