Reaction surface description of intramolecular hydrogen atom transfer in malonaldehyde

Abstract

Intramolecular H atom transfer in malonaldehyde is described using a reaction surface Hamiltonian. This model utilizes two large amplitude, reaction-coordinate-like degrees of freedom—i.e., a surface in the 3N–6 dimensional configuration space of an N atom system—with the remaining 3N–8 degrees of freedom being local harmonic motion away from this 2D surface. The two reaction surface degrees of freedom are chosen to be the two OH bond lengths, i.e., the bond being broken and the bond being formed. The present methodology is developed using 3N–6 internal coordinates, in contrast to our earlier reaction surface model [J. Chem. Phys. 81, 3942 (1984)] that utilized the 3N Cartesian coordinates. From our calculations we conclude that the bare barrier (i.e., with no zero point vibrational corrections) for the H atom transfer is between 6 and 7 kcal/mol.