Carbonyl Coupling Reactions Probe Oxide Surfaces

这项研究考察了二氧化钛表面上的羰基偶联反应的活性中心要求。目标是确定羧酸的酮化、羟醛缩合和羰基歧化的活性中心，并将这些反应发展为金属氧化物的化学和物理性质的探针。考察了稳定和亚稳态氧化物表面结构对反应活性的影响。探索了即使在超高真空下也可以进行的新的齐聚反应，从而展示了包括电子和离子光谱在内的表面科学方法在齐聚、聚合和歧化催化剂中的应用。使用双官能团的羧酸、醇和醛探讨了类似于观察到的分子间反应的分子内偶联反应的位置要求。利用扫描隧道显微镜对反应表面和相关的吸附体结构进行了成像。尽管这项工作解决了根本问题，但它应该会提高人们对许多重要工业过程的理解，从Ziegler-Natta聚合(用于制造聚乙烯和聚丙烯)到复杂生物分子的合成。这一结果也可能对传感器和分离设备的设计产生重大影响。

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.