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<P> Fluorine-18 labeled 6-fluoro-3, 4-dihydroxy-phenyl-L-alanine (6-FDOPA) has been used in conjunction with Positron Emission Tomography (PET) to study the dopamine metabolism in the living human brain and also to monitor gastrointestinal carcinoid tumors. Elemental fluorination of L-DOPA in anhydrous HF (aHF) or aHF/BF3 has been shown to be an efficient method for the synthesis of 6-fluoro-L-DOPA. Utilization of aHF, however, is not desirable in a hospital environment owing to its hazardous nature. This work has consequently focused on the development of new methodologies for the direct electrophilic fluorination of aromatic amino acids, which circumvent the use of aHF. </p> <p> The present work has shown that the reactivity and selectivity of F2 towards L-DOPA in CF3S03H is comparable to that in aHF. The discovery and versatility of this new synthetic procedure has led to the production of 6-[18F]fluoro-L-DOPA, 6[18F]fluoro-D-DOPA, 4-[18F]fluoro-L-m-tyrosine (4-FMT) and 6-(8F]fluoro-L-m-tyrosine (6-FMT) in high radiochemical yields that are not only suitable for small animal imaging, but are also suitable for clinical use in human subjects. Because of the low volatility of CF3S03H, its removal from the reaction mixture was accomplished by use of an anion exchange resin in acetate form. The syntheses of2-, 4-and 6-FMT were also achieved by the direct fluorination of m-tyrosine (MT) in H20. The effect of temperature on the fluorination of MT was investigated and it was shown that, unlike CF3S03H, optimal conditions in H20 were attained at elevated reaction temperatures. </p> <p> There have been several reports relating to the formation of [18F]OF2 as a major byproduct (up to 20%) in the gas phase nuclear reaction, 180(p,n)18F. This reaction is used for the routine production of [18F]F2 which, in tum, is utilized for the syntheses of PET tracers such as radiofluorinated aromatic amino acids. Because the reactivity of OF2 has been reported to be similar to that of F2, its selectivity as a fluorinating agent towards aromatic amino acids was investigated. The effect of solvent acidity on the fluorination of MT using OF2 was studied and it was shown that, in contrast with the reactivity of F2 in superacids, OF2 is a more efficient fluorinating agent in less acidic solvent media. The use of H20 as the solvent medium for fluorination ofMT resulted in the formation of 19FFMT isomers in 4.35 ±0.04% yield. Consequently, the potential use of OF2 as a fluorinating agent for aromatic amino acids was also investigated for L-phenylalanine, 3nitro-L-tyrosine, 4-nitro-DL-phenylalanine, L-DOPA, 3-0-methyl-L-DOPA, 3,4dimethoxy-L-phenylalanine, m-, p-and a-tyrosine. In these studies, the only aromatic system fluorinated by OF2 was MT, indicating that the presence of [18F]OF2 as a byproduct resulting from the nuclear reaction, 180(p,n)18F, does not have a significant impact on the syntheses of radio fluorinated aromatic amino acids that have applications in PET imaging. </p> / Thesis / Master of Science (MSc)

Both bromodeprotonation and bromodesulphonation occur during aqueous bromination of sodium p-methoxybenzenesulphonate, A, and potassium l-methylnaphthalene-4-sulphonate, B. Extensive kinetic studies reported here suggest that bromodesulphonation of A proceeds by a two-step process with Br2 as the brominating species, but do not completely exclude Br+ (or H2OBr+) acting in either a one- or two-step process. For B, the kinetic data can be interpreted by either a one- or two-step process with Br2 as the brominating species. Kinetic sulphur isotope effects have been measured for the bromodesulphonation of A and B and found to vary with bromide-ion concentration, thus strongly supporting the two-step process involving molecular bromine. The kinetic results for the bromodeprotonation of A cannot distinguish between a one- and two-step process involving Br2l the two-step mechanism has been confirmed by the observation of a variation in kinetic hydrogen isotope effect with bromide-ion concentration. / Thesis / Doctor of Philosophy (PhD)

by Jian Wang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (p. 154-171). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 193-221). Also available in electronic format on the Internet.

Yip, Ho-yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 181-201). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Contents --- p.vi / List of Figures --- p.x / List of Tables --- p.xvii / Abbreviations --- p.xix / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Polycyclic aromatic hydrocarbons (PAHs) --- p.1 / Chapter 1.1.1 --- Characteristics of PAHs --- p.1 / Chapter 1.1.2 --- Sources of PAHs --- p.2 / Chapter 1.1.3 --- Environmental fates of PAHs --- p.3 / Chapter 1.1.4 --- Effects of PAHs on living organisms --- p.5 / Chapter 1.1.4.1 --- General effects --- p.5 / Chapter 1.1.4.2 --- Effects on plants --- p.6 / Chapter 1.1.4.3 --- Effects on invertebrates --- p.7 / Chapter 1.1.4.4 --- Effects on fishes --- p.7 / Chapter 1.1.4.5 --- Effects on reptiles and amphibians --- p.8 / Chapter 1.1.4.6 --- Effects on birds --- p.9 / Chapter 1.1.4.7 --- Effects on mammals --- p.9 / Chapter 1.2 --- PAH contamination in Hong Kong --- p.10 / Chapter 1.3 --- Treatments of PAH contamination --- p.12 / Chapter 1.3.1 --- Physical treatments --- p.12 / Chapter 1.3.2 --- Chemical treatments --- p.13 / Chapter 1.3.3 --- Biological treatments --- p.14 / Chapter 1.4 --- Advanced oxidation processes (AOPs) --- p.16 / Chapter 1.5 --- Summary --- p.24 / Chapter 2. --- Objectives --- p.27 / Chapter 3. --- Materials and Methods --- p.28 / Chapter 3.1 --- Chemicals --- p.28 / Chapter 3.2 --- Photocatalytic reactor --- p.30 / Chapter 3.3 --- Determination of PAHs concentrations --- p.30 / Chapter 3.3.1 --- Extraction of PAHs --- p.30 / Chapter 3.3.2 --- Quantification of PAHs --- p.32 / Chapter 3.4 --- Optimization of physico-chemical conditions for PCO --- p.37 / Chapter 3.4.1 --- Determination of the reaction time for optimization of PCO --- p.37 / Chapter 3.4.2 --- Effect of titanium dioxide (Ti02) concentration and light intensity --- p.38 / Chapter 3.4.3 --- Effect of initial pH and hydrogen peroxide (H2O2) concentration --- p.38 / Chapter 3.4.4 --- Effect of initial PAHs concentration --- p.39 / Chapter 3.5 --- Toxicity analysis --- p.39 / Chapter 3.5.1 --- Microtox® test for acute toxicity --- p.39 / Chapter 3.5.2 --- Mutatox® test for genotoxicity --- p.42 / Chapter 3.6 --- Determination of total organic carbon (TOC) removal in optimized PCO --- p.43 / Chapter 3.7 --- Determination of degradation pathways --- p.43 / Chapter 3.7.1 --- Extraction of intermediates and/or degradation products --- p.45 / Chapter 3.7.2 --- Identification of intermediates and/or degradation products --- p.45 / Chapter 4. --- Results --- p.49 / Chapter 4.1 --- Determination of PAHs concentrations --- p.49 / Chapter 4.2 --- Optimization of extraction method --- p.49 / Chapter 4.3 --- Optimization of physico-chemical conditions for PCO --- p.49 / Chapter 4.3.1 --- Determination of the reaction time for optimization of PCO --- p.49 / Chapter 4.3.2 --- Effect of Ti02 concentration and light intensity --- p.60 / Chapter 4.3.3 --- Effect of initial pH --- p.88 / Chapter 4.3.4 --- Effect of initial H2O2 concentration --- p.99 / Chapter 4.3.5 --- Effect of initial PAHs concentration --- p.104 / Chapter 4.3.6 --- Improvements on removal efficiency (RE) after optimization --- p.113 / Chapter 4.4 --- Toxicity analysis --- p.122 / Chapter 4.4.1 --- Microtox® test for acute toxicity --- p.122 / Chapter 4.4.2 --- Mutatox® test for genotoxicity --- p.122 / Chapter 4.5 --- Determination of TOC removal in optimized PCO --- p.129 / Chapter 4.6 --- Determination of degradation pathways --- p.129 / Chapter 5. --- Discussion --- p.150 / Chapter 5.1 --- Determination of PAHs concentrations --- p.150 / Chapter 5.2 --- Optimization of extraction method --- p.150 / Chapter 5.3 --- Optimization of physico-chemical conditions for PCO --- p.151 / Chapter 5.3.1 --- Determination of the reaction time for optimization of PCO --- p.151 / Chapter 5.3.2 --- Effects of Ti02 concentration and light intensity --- p.152 / Chapter 5.3.3 --- Effects of initial pH --- p.160 / Chapter 5.3.4 --- Effects of initial H202 concentration --- p.163 / Chapter 5.3.5 --- Effects of initial PAHs concentration --- p.165 / Chapter 5.3.6 --- Improvements on RE after optimization --- p.167 / Chapter 5.4 --- Toxicity analysis --- p.169 / Chapter 5.4.1 --- Microtox® test for acute toxicity --- p.169 / Chapter 5.4.2 --- Mutatox® test for genotoxicity --- p.170 / Chapter 5.5 --- Determination of TOC removal in optimized PCO --- p.171 / Chapter 5.6 --- Determination of detoxification pathways --- p.172 / Chapter 6. --- Conclusion --- p.177 / Chapter 7. --- References --- p.181 / Chapter 8. --- Appendix I --- p.202

published_or_final_version / Chemistry / Master / Master of Science

published_or_final_version / Chemistry / Master / Master of Science

No description available.

No description available.