Carbonyl Coupling Reactions Probe Oxide Surfaces

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This research examines the active site requirements for carbonyl coupling reactions on titania surfaces. The goals are to identify the active sites for ketonization of carboxylic acids, aldol condensation, and carbonyl metathesis, and to develop these reactions as probes of the chemical and physical properties of metal oxides. The influence of surface structure on reactivity is examined on both stable and metastable oxide surfaces. New oligomerization reactions that can be carried out even under ultrahigh vacuum are explored, thereby demonstrating the application of surface-science approaches, including electron and ion spectroscopies, to oligomerization, polymerization, and metathesis catalysts. Site requirements for intramolecular coupling reactions analogous to observed intermolecular reactions are probed using difunctional carboxylic acids, alcohols, and aldehydes. Structures of reactive surfaces and associated adsorbates are imaged by scanning tunneling microscopy. Although this effort addresses fundamental questions, it should improve understanding of many important industrial processes, ranging from Ziegler-Natta polymerization (used to make polyethylene and polypropylene) to the synthesis of complex biomolecules. The results could also have a major impact on the design of sensor and separation devices.