An experimental (NMR) and theoretical (GIAO) study of the tautomerism of benzotriazole in solution
The 1H, 13C and 15N chemical shifts of benzotriazole and its adducts with acetone have been measured. Using dynamic 13C NMR spectroscopy in the +30/−90°C range, the barrier to prototropy in benzotriazole has been determined (10.8 kcal mol−1 at 294 K). The thermodynamic parameters corresponding to the equilibria between benzotriazole and its two acetone adducts have been measured. GIAO calculations (B3LYP/6-311++G∗∗) have been carried out on 1H-benzotriazole tautomer: they provide a sound basis for signal assignment of all the nuclei.