Valence bond mixing and curve crossing diagrams in chemical reactivity and bonding

This chapter discusses the reactivity paradigms; the Valence Bond (VB) mixing diagrams that have been developed to answer a fundamental question of chemical reactivity: “What are the origins of the barrier in a chemical reaction, and what is the mechanism of transition state formation?” If a mechanism of barrier formation exists, the structure and energy of the transition state can be analyzed, and relationships that may exist between the transition state and properties of its precursor and successor reactants and products can be predicted. This chapter provides an overview of the current knowledge on the qualitative applications and quantitative implementations of the VB mixing ideas. It also describes the key elements of the VB mixing diagrams and their principles of applications to chemical problems. Most of the applications are within the domain of chemical reactivity, but some problems of bonding and structure, which can be couched as chemical transformations bearing similarity to a chemical reaction, are also discussed. © 1995 Academic Press Inc.