The Chemical Catalysis Program supports Professor Robert J. Madix at Harvard University for a research project that will develop the fundamental basis for simple, novel heterogeneously catalyzed reactions for the transformation of amides, imines, nitriles and aziridines over copper, silver and gold surfaces through understanding of the kinetics and mechanism of the surface reactions of nitrogen-containing molecules. The proposed studies are based on fundamental principles of surface reactivity discovered and developed in previous NSF-supported work. Amidization, iminization, nitrilation and aziridination reactions facilitated by these group IB metals will be studied utilizing well defined single crystal surfaces. This research will provide a molecularly based understanding of the elementary reaction steps of these complex synthesis reactions. They have the potential for transforming existing technologies into more energy efficient and environmentally benign processes.
With the support of the Chemical Catalysis Program in the Chemistry Division at the National Science Foundation, Dr. Madix will perform research that will have a significant impact on important chemical transformations for the industrial sector with significant outcomes of improved catalyst selectivity, reduced waste, and potentially lower energy consumption. The proposed research is important to the development of processes critical to maintaining leadership in the multibillion dollar chemical industry in the United States and to the reduction in energy use. Broader impacts of the research has as an outcome the training and professional development of postdoctoral students and the training of both women and minority students. Professor Madix will include undergraduates in his research through the REU program at Harvard and will conduct coordinated activities with local high schools to stimulate the interest of minority high school students in physical science. Harvard University's existing partnerships with both The Engineering School at the Hyde Park Educational Complex in Boston and the Cambridge Rindge and Latin School will be utilized.
The production of basic chemicals to useful materials over the surfaces of solids is known as heterogeneous catalysis and is an essential link in the production of nearly all chemicals. The research conducted under this grant has addressed the use of new catalytic materials, namely, alloys of silver and gold, in the synthesis of species that require the coupling of separate molecular species. We have examined the basic pathways to the oxygen-assisted synthesis of mixed amides and esters over silver, gold and silver/gold alloy surfaces. The results show that the formation of atomic oxygen on the surface due to dissociation of dioxygen in the gas phase leads to a sequence of reactions involving specific adsorbed intermediates, each of which has been identified. For example, couplling of formaldehyde with dimethyl amine first involves the activation of the N-H bond in the amine to form dimethyl amide attached to the surface. This amide is attacked by the aldehyde to form a hemiaminal, which then eliminates hydrogen to product the amine. Knowledge of these reaction steps leads to the generalization of reaction pattern that afford the prediction of many similar synthesese beyond the reactions studied. It has also been shown that relatively weak intermolecular interactions, previously ignored for such processes, actually determine the prevelant surface reaction pathways for competing processes. The result of these studies, which are fundamental in nature, have direct applicability to practical catalytic implementation of the materials studied.
