Reaction dynamics study on the tunneling effects of a microsolvated E2 reaction: FO-(H2O)+C2H5Cl -> HOF(H2O)+C2H4+Cl-

Dual-level variational transition state theory with semiclassical tunneling (VTST/ST) calculation has been performed on the gas-phase microsolvated E2 reaction of FO-(H2O) + C2H5Cl. The high-level data are obtained using corr elated extended-basis-set electronic structure calculations and the low-lev el potential energy surface is based on a PM3-SRP method. The classical bar rier of the reaction is estimated to be 3-5 kcal/mol. The rate constants an d the kinetic isotope effects (KIEs) were calculated from 200 to 800 K. Tun neling effects are found to contribute significantly to the rate constants at low temperatures in most cases. Interestingly, the tunneling effects con tribute very inversely to the calculated KIEs at lower temperatures. The so lvent kinetic isotope effects (SKIEs) are also calculated as a function of temperature at different barrier heights in the estimated barrier range. It is found that tunneling contributes normally to the inverse SKIEs. The res ults from the current study suggest that the tunneling effects in E2 reacti ons make both KIEs and SKIEs less pronounced at lower temperatures.