Theoretical study of synthetic reaction of tetrazole and tetrazolate anion

Tetrazole (H 2 CN 4 ) and tetrazolate anion (HCN \documentclass{article}\pagestyle{empty}\begin{document}$_{4}^{-}$\end{document} ) are high‐energy compounds with a five‐membered ring‐type structures, which can be easily synthesized by HCN and HN 3 and by HCN and N \documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{-}$\end{document} , respectively, in an irreversible reaction. The ab initio methods including MP2/6‐31G**, B3LYP/6‐31G**, B3LYP/6‐311+G(2d,p), and CBS/QB3 from Gaussian 98 program are employed to study the thermochemistry and reaction mechanism. The transition states of both HCN + HN 3 → H 2 CN 4 and HCN + N \documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{-}$\end{document} → HCN \documentclass{article}\pagestyle{empty}\begin{document}$_{4}^{-}$\end{document} reaction are investigated, and it is found that the latter reaction is more favored than the former one in view of the chemical kinetics and thermodynamics, thus indicating that tetrazole (H 2 CN 4 ) and tetrazolate anion (HCN \documentclass{article}\pagestyle{empty}\begin{document}$_{4}^{-}$\end{document} ) are formed more easily in an alkali environment than in other systems. Pentazole (HN 5 ) is an unknown high‐energy compound and has not yet been synthesized. For comparison, HN 5 and N \documentclass{article}\pagestyle{empty}\begin{document}$_{5}^{-}$\end{document} , both which have similar type of synthetic reactions to the above‐mentioned reactions, are studied. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 27–37, 2000