The mechanism and kinetics of decomposition of 5-aminotetrazole

Abstract

The pathway and ab initio direct kinetics of the decomposition 5-aminotetrazole (5-ATZ) to HN₃ and NH₂CN was investigated. Reactant, products and transition state were optimized with MP2 and B3LYP methods using 6–311G** and aug-cc-pVDZ basis sets. The intrinsic reaction coordinate curve of the reaction was calculated using the MP2 method with 6–311G** basis set. The energies were refined using CCSD(T)/6–311G**. Rate constants were evaluated by conventional transition-state theory (CVT) and canonical variational transition-state theory (TST), with tunneling effect over 300 to 2,500 K. The results indicated that the tunneling effect and the variational effect are small for the calculated rate constants. The fitted three-parameter expression calculated using the CVT and TST methods are ${\text{k}}\left( {\text{T}} \right) = 4.07 \times 10^{11} \times {\text{T}}^{0.84} \times {\text{e}}^{\left( {{{ - 2.42 \times 10^4 } \mathord{\left/ {\vphantom {{ - 2.42 \times 10^4 } {\text{T}}}} \right. \kern-\nulldelimiterspace} {\text{T}}}} \right)} {\text{s}}^{ - 1}$ and ${\text{k}}\left( {\text{T}} \right) = 2.09 \times 10^{11} \times {\text{T}}^{0.89} \times {\text{e}}^{\left( {{{ - 2.36 \times 10^4 } \mathord{\left/ {\vphantom {{ - 2.36 \times 10^4 } T}} \right. \kern-\nulldelimiterspace} T}} \right)} {\text{s}}^{ - 1}$ , respectively.