UC Santa Barbara

In this paper we compare a recently presented approach to the determination of symmetry rules for chemical reactions based on adiabatic electronic states to earlier work in which a quasiadiabatic representation was used. The adiabatic approach is shown not to lead directly to Woodward–Hoffmann symmetry rules, and a number of the conclusions of the adiabatic work are shown to be incorrect and inconsistent. An indirect approach for deriving the Woodward–Hoffman rules in the adiabatic representation is presented which uses the connection between the adiabatic and quasiadiabatic representations to relate barrier height to the quasiadiabatic electronic matrix elements.