The Reactivity of 5-Cyanotetrazole towards Water and Hydroxylamine

Abstract

Sodium 5-cyanotetrazolate sesquihydrate (1) was prepared from sodium azide and two equivalents of sodium cyanide under acidic conditions. Its hydrolysis, when treated with an excess of 6 M nitric acid yields tetrazole-5-carboxamide (4), whereas stoichiometric amounts of 2 M nitric acid yields the free acid 5-cyanotetrazole (2). 5-Cyanotetrazole readily reacts with hydroxylammonium chloride to form the oxime of tetrazole-5-carboxamide (6). Both compounds, the tetrazole-5-carboxamide (4) and its oxime (6), bear an acidic proton, which can be abstracted with bases such as aqueous ammonia or hydroxylamine, to form the respective hydroxylammonium (5, 7) or ammonium salts (8). Also the guanidinium (9) and the triaminoguanidinium salt (10) were prepared using guanidinium and triaminoguanidinium chloride, respectively. All mentioned compounds, including the silver salt of 5-cyanotetrazole (3), were structurally characterized by low-temperature single-crystal X-ray analysis. In additional, the materials were characterized using NMR and vibrational (IR, Raman) spectroscopy as well as mass spectrometry and elemental analysis. The thermal behavior was studied from DSC measurements and the sensitivities of the compounds towards shock, friction, and electrostatic discharge were determined. Moreover, the heats of formation were calculated (atomization method, CBS-4M enthalpies) and several detonation/propulsion parameters computed with the EXPLO5 code.