A computational study on the 5-substituted 1H-tetrazoles: Structure, stability and aromaticity

The tetrazole moiety exhibits a wide and growing number of applications. This nitrogen-rich system is used in propellants, explosives and pharmaceuticals.A tetrazole molecule has prepared via [3+2] cycloaddition reaction starting from nitrile and sodium azide.The mechanism of tetrazole formation was studied theoretically by Barry Sharpless.In the present paper, the stabilization energy values of 5-substituted 1H-tetrazoles have been computed by the application of density functional theory (DFT) method by proper isodesmic reactions. Total energies, nucleus-independent chemical shift (NICS) and HOMO-LUMO gaps values have been calculated in order to determination of the stability, aromaticity and reactivity for the 5-substituted 1H-tetrazoles. an‎d also, the geometrical parameters have been used for confirmation of observations.The isodesmic reactions revealed that tetrazoles containing electron-donating substituents have great stabilization energies, while the molecules containing electron-withdrawing substituents have low stabilization energies. It is deduced from the NICS data that the aromaticity of molecules decreases with increasing the interference of ring current. The HOMO-LUMO gaps calculation showed that 5-nitro-1H-tetrazole is more reactive than other tetrazole derivatives.