Etude de l'équilibre dans les oxazolo[2,3-e], thiazolo[2,3-e] et isoxazolo[2,3-d]tétrazoles. II. Etude de l'effet de la température par dipolemetrie et résonance magnétique nucléaire

Abstract

The equilibrium constant in dioxane between azido and tétrazole isomers has been obtained for five heterocyclic azides (2-azido thiazoles, benzothiazole, benzoxazole, and 3-azido isoxazole) by proton nmr and dipole moment- studies. The last method involves a comparison between experimental and calculated (INDO, CNDO/2, CNDO/S) dipole moments. The CNDO/S method gives the best equilibrium constants and entropy factor (ΔS ∼ 50 J K−1 mol−1). A value of 114° for the C—N—N angle is found to account satisfactorily for certain properties (energy, dipole moment, photoelectron spectra) of aromatic azides. The heterocyclic azidoimines prefer the Z conformation.