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Dissertation/Thesis Abstract

Study of the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Hydride Transfer Reactions in Solution
by Ma, Li, M.S., Southern Illinois University at Edwardsville, 2018, 111; 10843728
Abstract (Summary)

It has been accepted that hydrogen-transfer reactions take place through a quantum mechanical tunneling mechanism, where H tunnels through its classical energy barrier in light of its wave form. There are several H-tunneling models proposed, including the contemporary Marcus-like H-tunneling model, which explains that the donor-acceptor distance (DAD) in the tunneling ready state (TRS) is shorter for a heavier isotope (e.g. deuterium (D)) then a lighter isotope (e.g., protium (H)). This model has been used to explain the kinetic isotopic effect observations in H-tunneling processes to provide mechanistic role of protein in enzyme catalysis. The purpose of the research is to test the hypothesis of “isotopically different DAD” concept by studying the hydrogen/deuterium-transfer reactions in solutions, given that hydride-transfer reactions account for over 50% of biological reactions. Our group’s previous results showed that the steric hindrance and hydrogen-bonding effect played a significant role in the different hydrogen vs deuterium tunneling-ready states. In general, the shorter DAD creates more spatial crowding effect which will affect the 2° C-H vibrations and decrease the 2° KIEs. In this thesis, different reaction systems were designed to test these effects by studying the 1° isotope dependence of 2° KIEs at the near and remote positions from the reaction center. It was found that the results are consistent with the hypothesis of the “isotopically different TRS structures”.

Indexing (document details)
Advisor: Lu, Yun
Commitee: Shaw, Michael, Tucker, Kevin
School: Southern Illinois University at Edwardsville
Department: Chemistry
School Location: United States -- Illinois
Source: MAI 58/01M(E), Masters Abstracts International
Subjects: Chemistry
Keywords: Donor-acceptor distance, H-tunneling, Hydride transfer reactions, Primary isotope dependence, Secondary kinetic isotope effects, Steric hindrance
Publication Number: 10843728
ISBN: 978-0-438-35203-2
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