Rapid Kinetics by Stopped-Flow NMR

分析和表面化学项目的资金支持威斯康星大学麦迪逊分校的克拉克·兰迪斯教授利用核磁共振光谱研究快速化学反应动力学的努力。这项研究通过探索停流核磁共振技术的所有关键要素：理论、计算模型、探针构造和评估以及在化学反应中的应用，将核磁共振光谱的信息丰富特性与快速动力学能力相结合。探测器建造活动的重点是将停流反应技术与流动核磁共振能力相结合。亥姆霍兹线圈和环形腔谐振器都在开发中，目标是将可到达的反应半衰期从大约100秒降低到几毫秒。这两种类型的流动探头都将配备实用的驱动系统，并能够处理空气敏感试剂。实际实现停流核磁共振能力需要了解光谱如何受到反应动力学和各种伪影的影响。根据任意动力学模型对实验数据进行模拟和拟合的计算程序正在开发、验证和传播。停流核磁共振通过对金属催化的烯烃聚合等快速催化过程的动力学研究来说明其威力。由于核磁共振方法可以普遍应用，因此所提出的研究的影响跨越了不同的动力学过程，如蛋白质折叠、催化转化(如酶、有机金属或有机催化)和其他化学反应。这项研究的产品包括：(1)向研究界介绍核磁共振研究快速反应的能力的出版物；(2)模拟快速反应的核磁共振谱的软件方法；(3)基于流动探头的改装或新环腔的构建的新核磁共振探针的详细计划和性能评估；以及(4)关于化学动力学和核磁共振方法的新课堂材料。人力资源的发展，主要是本科生和博士后研究人员的密切接触，导致了对从电子学到流动动力学和化学催化等一系列异常广泛的研究问题的密切接触。

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.