Insights into the mechanisms of chemical reactions. Reaction paths for chemical reactions

Abstract

The concept of a reaction path which continuously describes the transformation of reactants to products is firmly embedded in the lore of chemistry. A formal definition of the reaction path for a general molecular system was proposed by Fukui in 1970 as the path of steepest descent in mass-weighted cartesian coordinates from the transition state to reactants in one direction and to products in the other. In 1980 Miller, Handy and Adams advanced a formal theory of reaction dynamics based on harmonic fluctuations about the reaction path. We report reaction paths for two prototypical chemical reactions: Li + HF, an electron-transfer reaction, and OH + H₂, an abstraction reaction. In the first we consider the connection between the energetic terms in the reactions path Hamiltonian and the electronic changes which occur upon reaction. In the second reaction we consider the treatment of vibrational effects in chemical reactions in the reaction-path formalism.