Quantum Mechanical Dynamics of Hydride Transfer in Polycyclic Hydroxy Ketones in the Condensed Phase

We have used correlated electronic structure calculations and direct dynamics methods, including variational transition state theory with multidimensional semiclassical methods for calculating tunneling probabilities, to predict kinetic isotope effects (KIEs) and activation energies for hydride transfer in a polycyclic hydroxy ketone in the gas phase and aqueous solution. The need to include tunneling in the calculation of the KIEs has been shown, and the enhanced tunneling arising from a multidimensional model, compared to the one-dimensional Wigner treatment, has been demonstrated. The effect of solvent on the multidimensional tunneling contributions to the KIEs is significant and partly cancels the other contributions of the solvent to the KIEs. We also examined structural features on the kinetics for three other polycyclic hydroxy ketones by using conventional transition state theory and a Wigner tunneling approximation.