Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.795640
Title: Spectroscopy at microwave and radio frequencies
Author: Moore, Kenneth W.
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1968
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Abstract:
Part A introduces the origin of proton chemical shifts and coupling constants, and discusses the significance of these quantities for studies of conformation and configuration in organic molecules. The general theories of chemical shifts and coupling constants are then applied to pyranosides and in particular to the high resolution proton magnetic resonance spectra of saturated deuterochloroform solutions of the four compounds: A: methyl 2-acetoxymercuri-2-deoxy-beta-D-glucopyranoside triacetate. B: methyl 2-chIoromercuri-2-deoxy-beta-D-glucopyranoside triacetate. C: methyl 2-chloromereuri-2-deoxy-alpha-D-mannopyranoside triacetate. D: methyl 2-chloromercuri-2-deoxy-alpha-D-talopyranoside triacetate. Compounds containing pyranoside rings exist usually in one of the two possible chair conformations, designated by Reeves as Cl and 1C: other things being equal, the Cl conformation is preferred for most D-hexoses and their derivatives. The spectra of the four compounds have been analysed, fully for the ring proton absorptions, using programs written for the DEUCE and KDF 9 computers in Glasgow University. The chemical shifts and coupling constants resulting from the analyses are given. Interpretation of these chemical shifts and coupling constants has confirmed that the compounds do have the structures and configurations described by A, B, C and D above. This is especially important for compound C, about whose configuration there has been some controversy. The ring proton coupling constants in particular show that compounds A, B, and C in saturated deuterochloroform solution have essentially C1 chair forms, with some distortion, and that compound D exists as a very distorted Cl chair conformer, almost in a half-boat conformation: some of these conclusions are supported by X-ray analyses. Apart from the analysis of the ring proton absorption peaks, the methoxy proton chemical shifts agree well with previous findings concerning this substituent, and the acetoxy proton chemical shifts are not inconsistent with the results of other workers. No spin-spin coupling between mercury isotopes and the protons H(1), H(2) or H(3) has been explicitly observed. The peaks in the spectrum of compound D are broadened slightly relative to the peaks in the spectra of the other compounds. This may be because of kinetic effects involving the presence in low concentration of another conformer in the solution, or to unresolved couplings, perhaps long-range proton-proton couplings. In Part B, nuclear quadrupole resonance (NQR) spoctroaccpy is introduced, and quadrupole resonance is treated theoretically, with special reference to the 14N nucleus. A description is given of the two main types of instrument used to detect NQR: the marginal oscillator and the super-regenerative oscillator. Modulation is discussed. Two complete spectrometer systems for detection of NQR have been designed and constructed, and details of these systems are given. The first system uses a marginal oscillator; the second uses a super-regenerative oscillator which is externally quenched. In Part C, the factors which contribute to the electric field gradient tensor and so to the NQR frequencies in an isolated molecule are analysed. Methods of finding various molecular and atomic parameters which are needed for estimating the contributions of these factors are reviewed and discussed, and a few possible extensions or modifications of some of those methods are suggested. Mathematical techniques for evaluating the integrals which come out of these methods are also briefly reviewed, Intermolecular effects on the electric field gradient tensor are discussed briefly. The results are then given of the application to some simple molecules of the methods described and suggested earlier, with some further discussion of points of important detail. These results seem to be promising enough to justify a proper, more detailed, study of the possibilities of semi-empirical calculations of NQR frequencies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.795640  DOI: Not available
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