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|Title:||Nitrogen-14 Nuclear Quadrupole Resonance Studies of Pyrimidine and Purine Derivatives|
|Author(s):||Mccullen, William Lynwood|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The classical and quantum mechanical descriptions of nuclear quadrupole resonance (nqr) are reviewed. Fundamental principles of nuclear spin thermodynamics are introduced to explain double resonance via level crossing (drlc), the experimental technique employed to detect ('14)N nqr resonances.
Two double irradiation techniques are described which enhance spectral intensity and resolution. The first technique, "sensitivity enhancement", which was previously reported in the literature, affords a means of selectively enhancing the intensity of inherently weak (nu)(,-)resonances. The second technique, "pre-saturation", provides a method of resolving two intense, overlapping resonances which arise from different nitrogen sites.
A simple model is developed from non-degenerate perturbation theory to describe the 'solid effect'. The model qualitatively accounts for the characteristic line shapes associated with various types of nitrogen sites and the unresolved fine structure associated with resonances arising from the nitrogens of primary amine groups.
Finally, the ('14)N nqr parameters for a number of pyrimidines and purines are reported. A Townes-Dailey model is presented which relates the nqr parameters with the relative nitrogen atom hybrid orbital populations for the sp('2) orbitals of the cyclic amino, cyclic imino, exocyclic amino nitrogen sites. The population trends are discussed in terms of intramolecular resonance and inductive effects, and intermolecular bonding interactions. The ('14)N nqr spectra were obtained for several diamagnetic metal-pyrimidine compounds. With the exception of dichlorouracilcadmium, unambiguous assignment of these spectra was not possible.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
|Date Available in IDEALS:||2014-12-13|