DIRECT AND COMPLEX-FORMING COLLISIONS IN A COLLINEAR MODEL FOR THE BARRIERLESS PROTON-TRANSFER REACTION CH3OH+-OCH3-]CH3O-+HOCH3

A simplified collinear model for the title reaction is studied using classical trajectory methods. By treating the methoxy groups as united atoms, we reduce the reaction to a three-body heavy-light-heavy system. At low collision energies, both long-lived, complex-forming collisions and 'direct' collisions are observed. The reaction probability for direct collisions is considerably lower than the statistical value 0.5 found for complex trajectories. The observed behavior is analyzed in terms of the phase space structure of the collinear heavy-light-heavy system.