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Dissertation/Thesis Abstract

Primary Isotope Dependence of Secondary Kinetic Isotope Effects in a Hydride-Transfer Reaction in Solution
by Lefton, Jonathan, M.S., Southern Illinois University at Edwardsville, 2015, 96; 10013990
Abstract (Summary)

The Lu group at SIUE recently proposed a hypothesis in which H- and D-tunneling reactions have tunneling ready structures with different donor-acceptor distances (DADs) and a pronounced 1° isotope effect on 2° KIEs should be observed in tunneling systems that are sterically hindered. Previously, the hypothesis was tested by studying the 1° isotope dependence of α- and β-type 2° KIEs for a series of hydride transfer reactions in acetonitrile and found the 2° KIE at the sterically accessible γ-2° CH3/CD3 is more sensitive to the 1° isotope effect than that at the sterically inaccessible ?-2° H/D groups. Primary isotope dependence was explained using the concept of isotopically different tunneling-ready state structures. D-tunneling has a crowded environment that stiffens the N-CH3 vibrations decreasing the 2° KIE. However, the literature study of the hydride transfer reaction between 5-methyl-5,6-dihydrophenanthridine (MPH) and 10-methylacridinium (MA +) showed that the γ-2° KIE at the 9-H/D position of MA + was significantly affected by the 1° isotope. The work described in this thesis reinvestigated the 1° isotope effect on the 2° KIEs for the reaction in both the solvent that those authors used and that we use. We found that no effect could be observed in both solvents. We also determined the 1° isotope dependence of the γ-2° KIE at the 5-N-CH3/CD3 position of MPH and found a significant effect, which also supports our hypothesis. The γ-2° KIEs bear large errors, which are likely attributed to possible decomposition of reactants, as the measurements were made several months after the other measurements.

Indexing (document details)
Advisor: Lu, Yun
Commitee: O'Brien, Leah, Shaw, Michael
School: Southern Illinois University at Edwardsville
Department: Chemistry
School Location: United States -- Illinois
Source: MAI 55/03M(E), Masters Abstracts International
Subjects: Biochemistry
Keywords: Hydride-transfer reaction, Kinetic isotope effects, Steric isotopes
Publication Number: 10013990
ISBN: 978-1-339-48265-1
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