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.
|Commitee:||O'Brien, Leah, Shaw, Michael|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 55/03M(E), Masters Abstracts International|
|Keywords:||Hydride-transfer reaction, Kinetic isotope effects, Steric isotopes|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be