Probing Transition States on Metal Surfaces

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An examination of the transition states of surface reactions forms the focus of this research project supported by the Analytical and Surface Chemistry Program and the Office of Multidisciplinary Activities. Professor Gellman and his students at Carnegie Mellon University are addressing the nature and energetics of the transition state in various elementary surface reaction processes including -hydride elimination, alkyl coupling and phenyl coupling reactions on Cu and Ag surfaces. The transition state is probed by fluorine substitution of reactants and the monitoring of reaction kinetics and mechanism using vibrational spectroscopy and thermal desorption spectroscopy. Activation barriers and energetics obtained experimentally will be compared with computational investigations of transition state energetics. The use of the methods of physical organic chemistry to examine transition states in surface reactions is the subject of this research project. Fluorine substitution is used to probe the stability and energetics of the transition state for various hydrogen elimination and coupling reactions occurring on copper and silver surfaces. This information will provide the thermodynamic background essential for an understanding of catalytic chemistry on these surfaces, as well as for similar processes in electrochemical and corrosion environments.