Chemical Kinetics in Theory
One way to approach the theoretical study of chemical reactions is to bring the reactants together in well-defined crossed molecular beams. Then energy allocations to reactant and product molecules can be calculated with a kinematic analysis, as will be shown in Sec. 11.1 and in the program Newton. Beneath the kinematics lies reaction dynamics and its principle theoretical tool, the potential energy surface. A simple method for constructing potential energy surfaces is described in Sec. 11.2, and the program Leps displays graphical representations. The course of a reaction is traced as a path on the potential energy surface, up the valley of the reactants, through a pass at the head of that valley, and down the valley of the products. The configuration of the reacting system at the saddle point in the pass defines the activated complex, which often behaves as if it were in equilibrium with reactant molecules. If so, a statistical method for estimating rate constants introduced by Eyring is applicable. Rudiments of Eyring’s theory are sketched in Sec. 11.3 and implemented for unimolecular and bimolecular reactions in the programs Eyring1 and Eyring2. Some features of the further theory of unimolecular reactions are mentioned in Sec. 11.4 and illustrated with the programs Beyer, Rrkm, and Whitten. We saw many examples of steady-state conditions in Chapter 10. Usually, as the name implies, steady states are stable, but not always.
KeywordsPotential Energy Surface Chemical Kinetic Bimolecular Reaction Unimolecular Reaction Calculate Rate Constant
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