INTRAMOLECULAR PROTON-TRANSFER DIRECT DYNAMICS IN THE GLYCOLATE ANION- ISOTOPE EFFECTS

We studied the dynamics of intramolecular proton transfer in the glyco late anion, and of the analogous processes in the deuterated and triti ated derivatives, by means of variational transition state theory with various multidimensional semiclassical models of tunneling. Rate cons tants were obtained directly from MP2/6-31++G* ab initio results scal ed so that the height of the barrier coincided with the value given by QCISD/6-31++G* calculations, 3.81 kcal/mol. In this kind of system, the effective barrier height can be significantly lower for the lighte r isotope. Analysis of the kinetic isotope effects (k(H)/k(D) and k(H) /k(T)) showed them reduced by tunneling but favored by certain vibrati onal modes. (C) 1997 American Institute of Physics.