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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

An investigation of enzyme mechanisms using substrate analogues

Potter, Barry V. L. January 1980 (has links)
The synthesis of several fluorinated analogues of thiamine and precursors has been undertaken, all of which exhibit weak activity against E.Coli. A route to 3-fluoro-(R)-alanine has been explored. The first synthesis of the enantiomeric fluorosuccinic acids has been accomplished, and a stereochemical analysis has shown that synthesis via esterified malate precursors using diethylamino- sulphurtrifluoride gives inversion of configuration, whereas prep- aration via aspartic acid and polyhydrogen fluoride in pyridine gives retention of configuration. The circular dichroism spectra of the fluorosuccinic acids are anomalous, being the first example of such behaviour in a-substituted carboxylic acids and derivatives. A previously assigned configuration of a Pseudomonal metabolite ( + )- fluorosuccinic acid has been corrected. The fluorosuccinic acids are not substrates for malic enzyme, but are potent inhibitors of fumarase. Using (2S)-fluorosuccinic acid as a mechanistic probe the fumarase reaction is identified as a bimolecular E2 elimination. A stereochemical analysis of enzymic phosphoryl transfer reactions using CD spectroscopy has been investigated, and a new synthesis of inorganic pyrophosphate used to prepare P<sub>1</sub>=[(S)- <sup>16</sup>0, <sup>17</sup>0, <sup>18</sup>0]-pyrophosphate whose <sup>31</sup>P n.m.r. spectrum is discussed. The first example of 31 p- 17 o coupling as observed by 31 P n.m.r. is demonstrated.- The magnitude of the <sup>31</sup>P- <sup>18</sup>0 isotope shift is dependent on the nature of the phosphorus to oxygen bond. An elegant method for establishing the isotopic configuration of oxygen chiral phosphates by n.m.r. has been developed, requiring the synthesis of D-glucose-6[(S) - <sup>16</sup>0, <sup>17</sup>0, <sup>18</sup>0]-phosphate, adenosine-5'- [(S)- <sup>16</sup>0, <sup>17</sup>0, <sup>18</sup>0]-phosphate, and their six membered cyclic phosphate triesters. Chemical cyclisation of these molecules occurs both with racemisation and inversion of configuration at phosphorus. The chemical synthesis of adenosine-5'[ (S) - <sup>16</sup>0, <sup>17</sup>0, <sup>18</sup>0]- triphosphate has been achieved and exploited to demonstrate that hexokinase phosphoryl transfer proceeds with inversion of config- uration at phosphorus. Pyruvate kinase phosphoryl transfer from 2 [(S)- <sup>16</sup>0, <sup>17</sup>0, <sup>18</sup>0]-phospho- (R)-glycerate also proceeds with inversion of configuration, as does phosphofructokinase phosphoryl transfer from sn-glycerol-3[ (5)- <sup>16</sup>0, <sup>17</sup>0, <sup>18</sup>0]-phosphate.
32

Free-radical approaches to new fluorocarbon derivatives

Swales, Alan Peter January 1989 (has links)
This thesis is concerned with the free-radical addition of nitrogen, silicon and oxygen containing compounds to fluoroalkenes and the chemistry of some of the adducts produced. Free-radical adducts of many amines cannot be produced directly since nucleophilic attack on the fluoroalkene is often the preferred reaction pathway. An alternative route to primary and secondary mono-amine adducts via N-trimethylsilylamines has been developed. An alternative synthesis of di-amine adducts via amides has met with some success. Free-radical additions of organosilicon compounds to fluoroalkenes have produced a variety of fluorosilicon adducts. The chemistry of some of these adducts has been investigated. Work with mono- and di-oxygen functional compounds has provided information on the scope and limitations of this type of free-radical addition reaction. The dehydrofluorination of ether/hexafluoropropene mono- and di-adducts has been investigated and some novel dienes have been produced. Polymers containing amide or ether groups added to hexafluoropropene under free-radical conditions. The use of a solvent dramatically increased the degree of this incorporation. The electrochemical fluorination of cyclic ether/hexafluoropropene di-adducts has been investigated. Good recoveries of highly fluorinated products were obtained, indicating that these types of adducts are good starting materials for electrochemical fluorination.
33

The generation and chemistry of some novel perfluorinated dienes

Mullins, Steven John January 1992 (has links)
The work contained in this thesis is divided into three sections detailing the formation of fluorinated dienes and some aspects of their chemistry: a) Through cyclic voltammetry, an electrochemical investigation was carried out to determine the reduction potentials of several easily accessible perfluorinated alkenes. Following this, sodium amalgam was successfully used as a single electron transfer agent in order to reduce a number of these fluoroalkenes by means of selective defluorination. This has enabled a series of perfluorinated alkadienes to be prepared cleanly in good yield. A study of a variety of other means of defluorination was also investigated. b) These dienes have been subjected to attack by mono- and bi functional nucleophiles in high yielding reactions. This has enabled an unusual perfluorinated diepoxide to be synthesised which displays remarkable thermal stability. A number of novel pyrrole and pyrrolo-quinoline derivatives have also been made from a series of substituted anilines and these are discussed within a mechanistic framework in order to justify the product distributions. Finally, the reaction between potentially bi- functional carbon nucleophiles and these perfluorinated dienes has been used as a means of synthesising a series of poly(perfluoroalkyl)- substituted cyclopentadienyl anions including the pentakis(trifluoromethyl)-cyclopentadienyl anion, the formation of which could proceed by an unusual cyclisation and elimination mechanism. c) Charge transfer salts have been prepared by complexation of decamethylferrocene with various fluorinated dienes. These salts have been the subject of X-ray crystallographic and molecular magnetic susceptibility studies. No signs of organic ferromagnetism were observed.
34

Superconducteurs ioniques de structure fluorine : a) Mesure de la conductivité ionique du SrF à haute température : b) Etude des propriétés thermodynamiques du CaF par simulation numérique /

Evangelakis, Georges. January 1989 (has links)
Th. Univ.--Physique--Nancy 1, 1989. / Résumé en anglais. Bibliogr. p. 105-111.
35

New analytical methods for florine ...

Allen, Nelson, January 1933 (has links)
Thesis (Ph. D.)--Princeton University, 1933.
36

The effect of prior acid etch on the rate of Sn₃F₃PO₄ formation subsequent to topical SnF₂ treatment

Nordquist, William Dean. January 1973 (has links)
Thesis (M.S.)--University of Louisville, 1973. / Typescript (Xerox copy). Department of Oral Biology. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 87-100).
37

The effect of prior acid etch on the rate of Sn₃F₃PO₄ formation subsequent to topical SnF₂ treatment

Nordquist, William Dean. January 1973 (has links)
Thesis (M.S.)--University of Louisville, 1973. / Typescript (Xerox copy). Department of Oral Biology. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 87-100).
38

Studies on fluorine as a factor in the value of mineral phosphates in animal nutrition

Lamb, Alvin Romaine. January 1930 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1930. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 67-68).
39

The absorption spectra of fluorine and hydrogen fluoride in the vacuum ultraviolet

Iczkowski, Raymond Peter, January 1958 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 79-83.
40

The thermodynamics of fluorine-chlorine exchange reactions

Hood, George Clement, January 1951 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 92-94.

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