Transition States for Surface Reactions

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

This research project, carried out at Carnegie Mellon University in the laboratory of Professor Andrew Gellman, is supported in the Analytical and Surface Chemistry Program. It is focussed on the understanding and thermodynamic characterization of the transition state for surface catalyzed reactions. Using substituent effects on organic reactants, the nature and thermodynamic stability of the surface reaction transition state is probed for a series of test reactions. Varying degrees of fluorine substitution affects the activation energy and stability of the transition state for probe reactions including dechlorination of chlorofluorocarbons, deprotonation of carboxylic acids, and O-H bond cleavage in alcohols. Experimentally measured energetics are compared with the results of high level electronic structure calculations to interpret the nature of the surface reaction transition state. A detailed understanding of the transition state in surface catalyzed chemical reactions is useful in catalyst design and process optimization. By using physical organic concepts such as substituent effects on reaction rates, Professor Gellman and his coworkers are probing the nature of the surface transition state for a series of probe reactions. Results from these measurements are compared with calculations, in order to develop a general understanding of the nature of the surface reaction transition state.