Decomposition Mechanism of 5,5′-Bis(tetrazole)-1,1′-diolate(TKX-50) Anion Initiated by Intramolecular Oxygen Transfer

Abstract

Density functional theory calculations at the B3LYP/6-31+G** and B3LYP/6-311++G** levels were performed on thermal decomposition of 5,5′-bis(tetrazole)-1,1′-diolate(TKX-50) anion with an intramolecular oxygen transfer being an initial step. The results show that the intramolecular oxygen transfers are the rate-limiting steps for the decomposition of title anion with activation energies being in the range of 287–328 kJ/mol. Judged by the nucleus- independent chemical shift values, the formation of antiaromatic ring in transition state or the decrease of aromaticity of the tetrazole ring of the reactant makes somewhat contribution to the high potential energies of the rate-limiting transition states. However, the activation energies of the following N2 elimination through various pathways are in a low range of 136–166 kJ/mol. The tetrazole ring acts as an electron donor or acceptor in different pathways to assist the bond rupture or group elimination. The rate constants in a temperature range of 500–2000 K for all the intramolecular oxygen transferring reactions were obtained. The corresponding linear relationships between lnk and 1/T were established.