Synthesis, Characterization, and Properties of Di- and Trinitromethyl-1,2,4-Oxadiazoles and Salts

The syntheses of 3-trinitromethyl-(1,2,4-oxadiazol-5-one), its N-methyl derivative, and 5-methyl-3-trinitromethyl-1,2,4-oxadiazole are described. The synthetic strategy initially involved a ring-closing step to afford the oxadiazole acetic acid ethyl esters. The saponification of these compounds led to the formation of the acetic acid derivatives, which were nitrated in a mixture of acids to yield the trinitromethyl derivatives. The three energetic compounds showed good detonation performance [detonation velocity (V-Det): 8779-8804ms(-1)] as well as good specific impulses (I-s: 244-262s). Furthermore, by starting from the 1,2,4-oxadiazole ethyl esters, we were able to prepare the potassium, barium, and ammonium salts of various dinitromethyl-1,2,4-oxadiazoles. All compounds were comprehensively characterized by vibrational spectroscopy (IR, Raman), NMR spectroscopy, differential thermal analysis (DTA), elemental analysis, and single crystal X-ray diffraction.