Dissertation/Thesis Abstract

Primary Isotope Dependence of the Near and Remote Secondary Kinetic Isotope Effects in Hydride Transfer Reactions in Solution
by Jafari, Shabnam, M.S., Southern Illinois University at Edwardsville, 2016, 103; 10160596
Abstract (Summary)

Many observations in hydrogen (H-) transfer reactions cannot be explained by the classical transition state theory. Rather, these reactions take place by H-tunneling effect in terms of H’s non-classical wave property. The transferring isotopes (1°) have different wave property and this difference can have an effect on the 2° kinetic isotope effect (KIE). Previous 1°/2° Hydrogen coupled motion theory cannot explain the deflated 2° KIE (as compared to the classically predicted value) in the case of D-tunneling. A new theory that can explain the observation uses the concept that the donor-acceptor distance (DAD) for D-tunneling is shorter than that for H-tunneling and thus D-tunneling has a more crowded reaction site. The latter crowding effect likely restricts the 2° H’s vibration and causes a deflation in 2° KIE. Thus our hypothesis is that H- and D-tunneling have tunneling ready structures that have different DADs, and the 1° isotope effect on 2° KIEs should be more pronounced in tunneling systems that are sterically hindered. Our group has designed several hydride transfer reactions in solution to test this hypothesis by studying the 1° isotope effect on the α- and β-2° KIEs and the results support it. This thesis work studies the 1° isotope dependence of both the near (α- and β-) and remote (ϵ-) 2° KIEs in the designed hydride transfer systems. The results are consistent with the previous observations further supporting the isotopically different DAD concept.

Indexing (document details)
Advisor: Lu, Yun
Commitee: Khazaeli, Sadegh, Luesse, Sarah, O'Brien, Leah
School: Southern Illinois University at Edwardsville
Department: Chemistry
School Location: United States -- Illinois
Source: MAI 56/01M(E), Masters Abstracts International
Subjects: Biology, Biochemistry
Keywords: H-tunneling, Hydride transfer, KIE limits
Publication Number: 10160596
ISBN: 978-1-369-15503-7
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