Nitraminoazoles based on ANTA - A comprehensive study of structural and energetic properties

Since 5-Amino-3-nitro-1H-1,2,4-triazole (ANTA) is known to be a thermally very stable secondary explosive, our goal in this contribution was the synthesis of thermally stable but more powerful energetic compounds based on ANTA. Hence, we utilized ANTA to synthesize 5-nitramino-3-nitro-1H-1,2,4-triazole (1) by nitration with a mixture of concentrated sulfuric acid and 100 % nitric acid. ANTA was also methylated with dimethyl sulfate to yield 5-amino-1-methyl-3-nitro-1,2,4-triazole (2), which was then subsequently nitrated by using the method mentioned above to yield 1-methyl-5-nitramino-3-nitro-1,2,4-triazole (3). All three compounds were characterized by IR and Raman as well as multinuclear NMR spectroscopy. Additionally, X-ray crystallographic measurements of 1 and 3 were performed. The decomposition points of the compounds were found to be low for 1 (135 °C) and 3 (108 °C), despite the high thermal stability of ANTA (>220 °C) and 2 (294 °C). In order to increase the thermal stability of the compounds, nitrogen-rich salts of 1 and 3 with the ammonium, hydrazinium, guanidinium, aminoguanidinium, and triaminoguanidinium cations were prepared and fully characterized by means of vibrational and NMR spectroscopy, DSC measurements, and X-ray diffraction measurements. Additionally, the impact as well as friction sensitivities and the sensitivity against electrostatic discharge were determined by using standard BAM techniques. The standard heats of formation were calculated for selected compounds at the CBS-4M level of theory, which reveals high positive heats of formation for all compounds