Rapid Kinetics by Stopped-Flow NMR

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Funding from the Analytical and Surface Chemistry Program supports the efforts of Professor Clark Landis of the University of Wisconsin at Madison to study fast chemical reaction kinetics using nuclear magnetic resonance (NMR) spectroscopy. The research merges the information-rich nature of NMR spectroscopy with fast kinetics capabilities by exploring all critical elements of a stopped-flow NMR technique: theory, computational modeling, probe construction and evaluation, and application to chemical reactions. Probe construction activities focus on combining stopped-flow reaction technology with flow NMR capabilities. Both Helmholtz coil and toroid cavity resonators are being developed with the goal of lowering the range of accessible reaction half-lives from ca. 100 seconds to a few milliseconds. Both types of flow probe will be fitted with practical drive systems and the ability to handle air sensitive reagents. Practical realization of stopped-flow NMR capabilities requires understanding of how the spectra are affected by reaction kinetics and various artifacts. Computational procedures for simulation and fitting of experimental data according to any arbitrary kinetic model are being developed, verified, and disseminated. The power of stopped-flow NMR is illustrated by kinetic studies of fast catalytic processes such as metal-catalyzed alkene polymerization.Because the NMR method can be applied generally, impact of the proposed research spans diverse kinetic processes such as protein folding, catalytic transformations (such as enzymatic, organometallic, or organocatalytic), and other chemical reactions. Products of this research include (1) publications that educate the research community on the capabilities of NMR for studying fast reactions, (2) software methods for simulating NMR spectra of fast reactions, (3) detailed plans and performance evaluations of new NMR probes based on adaptation of flow probes or construction of new toroid cavities, and (4) new classroom materials concerning chemical kinetics and NMR methods. The development of human resources, primarily undergraduate and postdoctoral researchers, results from intimate exposure to an unusually broad array of research issues, ranging from electronics to flow dynamics and chemical catalysis.