Asymmetric Carbamate Derivatives Containing Secondary Nitramine, 2,2,2-Trinitroethyl, and 2-Fluoro-2,2-dinitroethyl Moieties

In this work, the syntheses of 2,2,2-trinitroethyl-(2-nitro-2-azapropyl)carbamate (5), its analogue 2-fluoro-2,2-dinitroethyl(2-nitro-2-azapropyl)carbamate (6), and the corresponding 2,2,2-trinitroethyl(2-nitro-2-azapropyl)nitrocarbamate (7) and 2-fluoro-2,2-dinitroethyl(2-nitro-2-azapropyl)nitrocarbamate (8) are presented. The compounds were characterized thoroughly by vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, differential scanning calorimetry measurements and single-crystal X-ray diffraction. In addition, the hitherto unknown low-temperature crystal structures of the starting materials 2-nitro-2-azapropyl chloride (1) and 2-nitro-2-azapropyl isocyanate (2) are presented. Owing to the positive oxygen balance of the carbamate derivatives, their suitability as potential oxidizers in energetic formulations with aluminium as the fuel is investigated and discussed. Standard enthalpies of formation were calculated at the CBS-4M level of theory. With these values and the experimental densities from room-temperature pycnometer measurements, several detonation parameters, such as the detonation pressures and velocities of the crude materials as well as the specific impulses of their formulations with aluminium, were computed by using the EXPLO5 (V6.01) computer program and compared with those of the corresponding mixtures with ammonium perchlorate as the oxidizer. Furthermore, the sensitivities towards impact, friction and electrostatic discharge were determined by using the BAM drop-hammer and friction tester as well as a small-scale electrical discharge device.