Hydride Transfer and Rates of Transport Across Synthetic Membranes

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This project by Dr. Maurice Kreevoy within the Organic Dynamics Program is aimed at a better understanding of an important organic reaction known as hydride transfer. The problem will be approached theoretically by calculation of the detailed reaction pathway, and also experimentally by the measurement of reaction rates. This work is quite significant in that the reaction to be studied is a prototype for enzyme catalyzed oxidation-reduction reactions. With the aid of the Truhlar POLYRATE program, a multi-dimensional potential surface will be generated for the hydride transfer reaction. Using variational transition state theory with least-action tunneling, it will be used to mimic the experimentally observed relationship between rate and equilibrium constants, the magnitude of primary and secondary hydrogen isotope effects, and the relation between primary isotope effects and equilibrium constants. In the second part of this project, the solvent dependence of the rate constant, primary kinetic isotope effect, and equilibrium constant of the model hydride transfer reaction between 1-benzyl-3-cyano- quinolinium ion and 10-methyl-9,10-dihydroacridine will be studied. The object of this investigation is as follows: to establish and test a model for the reaction that will facilitate the identification of dynamic solvent effects on reactivity; to determine a parameter proportional to such effects; and to compare it with current theory and other experimental measures of dynamic solvent effects. Dynamic solvent effects are those that are not accounted for in conventional, quasi-equilibrium, transition state theory.