| The surface chemistry of several classes of catalytically important molecules on palladium single crystals was pursued in this thesis research. The influence of surface structure and composition on reactions involving formation and scission of carbon-carbon and carbon-hydrogen bonds was investigated. These studies were performed under ultrahigh-vacuum (UHV) conditions on single crystals; some reactions, however, were studied at higher pressures on polycrystalline films.;Single-crystal surfaces of palladium were found to catalyze the dehydrogenation of organosilanes. For example, silacyclohexane chemisorbed on Pd(110) underwent dehydrogenation upon thermal desorption to form silabenzene.;Chemisorption studies of thiophene, 3-methylthiophene, and 2,5-dimethylthiophene were performed on clean and sulfided palladium single crystals. Desulfurization products were observed in the thermal desorption spectra of these molecules.;Mechanisms of carbon-hydrogen bond scission were investigated for a variety of methylsubstituted benzenes. The use of selectively labeled molecules revealed some degree of regiospecificity in C-H bond scission.;Reactions of acetylene on Pd(111), Pd(100) were studied using thermal desorption spectroscopy, chemical displacement reactions, and isotopic labeling techniques. Palladium single crystals were found to catalyze several reactions of acetylene, including trimerization to benzene, hydrogenation to ethylene, and hydrosilation with trimethylsilane. Several atoms such as Si, P, S, and Cl were found to have a profound influence on the catalytic activity of these surfaces.;Several reactions of unsaturated hydrocarbons were also investigated at higher pressures (10('-2) torr) on polycrystalline palladium films. A remarkable correspondence between these studies and UHV studies was observed. |
