Addition reaction of azoles to acetone-d6: NMR and computational studies

Abstract

The reactivity of imidazole, pyrazole, 1,2,4-triazole, 1,2,3-triazole, and tetrazole with acetone (propan-2-one) has been studied by ¹H and ¹³C NMR using acetone-d₆ as solvent at temperatures ranging from 173 to 300 K at 10 K intervals. Simultaneously, the reaction has been theoretically calculated at the B3LYP/6-311++G(d,p) level, and experimental and theoretical results have been compared. The equilibrium constants between azoles and adducts α,α-dimethyl-azole-methanol were analyzed, assuming that the straight part of the plots –R ln K_e vs. 1/T can be used to determine ΔH and ΔS. Calculated and experimental data are related, but the theoretical values are proportionally higher. The tautomerism of triazoles and tetrazole has been considered in order to discuss the reactions.