RUI: Isotopically Different Tunneling-Ready-State Structures in Hydride Transfer Reactions in Solution

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In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professors Yun Lu, James E. Eilers, and Kevin R. Tucker of the Department of Chemistry at Southern Illinois University Edwardsville are investigating how reactions in the human body work. Hydrogen transfer reactions are common in chemistry and biology. About 50% of the biological reactions in the body involve hydrogen transfer. This project may help scientists understand these biological processes. The project involves expertise in three different areas of chemistry (organic, analytical and computational). The chemistry department at Southern Illinois University Edwardsville (SIUE) holds workshops that target high school teachers in the St. Louis Metro-East area, which has a large African-American population living below the poverty line. This program provides an opportunity for the research teams to involve the high school teachers and their students in the project, preparing them for college and a STEM career. The project investigates a new concept in the contemporary models for hydrogen (H)-wave transfer, i.e., H-tunneling. The new concept is that H-tunneling and its heavier isotope (deuterium (D) or tritium (T))-tunneling have different donor-acceptor distance (DAD) at the tunneling-ready-state (TRS) structures due to different masses thus different wave properties. Since a heavier isotope possesses shorter wavelength, its transfer requires a shorter donor-acceptor distance (DAD). The confirmation of the concept could change the traditional views about the H-transfer chemistry and the theory of the kinetic isotope effects (KIE). The investigators use physical organic mechanistic analysis methods to distinguish the isotopically different TRS structures for various hydride- vs. deuteride-transfer reactions in solution. They plan to study the primary isotope dependence of the secondary KIEs to distinguish the isotopically different TRS conformations. They also investigate the primary isotope dependence of Hammett correlations to differentiate the isotopically different TRS electronic structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.