Theoretical studies of the equilibria between two enolic forms of asymmetric β‐diketones

Abstract

17O NMR chemical shifts of two frozen enols in hydrogen tautomerizations for asymmetric β-diketones were calculated at the Hartree–Fock and density functional B3LYP levels of theory using various basis sets. From the theoretical 17O chemical shifts of frozen enols, the equilibrium constants for the enol–enol equilibria were estimated and used for comparison with previous experimental results based on model shifts for the pure enol forms. The results show that our theoretical method can complement some inadequacies in the experimental NMR techniques in evaluating equilibrium constants of systems undergoing rapid dynamic equilibrium. Copyright © 2001 John Wiley & Sons, Ltd.