Ce mémoire décrit l'utilisation de la spectrométrie de masse en mode électrospray pour l'étude mécanistique de réactions catalytiques.Dans le premier chapitre, le mécanisme de la réaction de Wacker est étudié ; l'implication d'espèces dinucléaires en palladium, dans le cas de l'utilisation de la benzoquinone comme oxydant, est mise en évidence. La réoxydation du palladium avant la décomplexation du produit a également été établie.Le deuxième chapitre est consacré à l'étude mécanistique de l'oxydation de l'allylphénole en milieu aqueux. La détection d'un intermédiaire epoxyde confirme un mécanisme en cascade : isomérisation, epoxydation et solvolyse.L'étude du mécanisme de réactions de type Heck déshydrogénant représente le dernier chapitre, quatre intermédiaires clefs du cycle catalytique proposé, ont été détectés. / This thesis describes the use of electrospray spectrometry for mechanistic studies of catalytic reactions. The mechanism of the Wacker reaction has been studied in the first chapter ; the implication of dinuclear palladium species, using benzoquinone as oxidant, has been demonstrated. The reoxidation of the palladium before the decoordination of the product has also been established. The second chapter focuses on the mechanism study of the oxidation of allylphenol in aqueous media. The detection of an epoxyde as intermediate corroborates the proposed mechanism : isomerisation, epoxydation solvolysis. The mechanism of a Dehydrogenative Heck reaction is described in the last chapter. Four key intermediates of the catalytic cycle have been identified.

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Arsenic is a widespread environmental contaminant whose toxicity depends on its valence and its chemical form. Arsenic species have been typically determined using high pressure liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICPMS), however ICPMS cannot differentiate the co-eluting arsenic species. This thesis explores the use of electrospray mass spectrometry (ESI-MS) with HPLC separation for arsenic speciation and demonstrates applications of various HPLC-ESI-MS methods for the determination of toxicologically and environmentally relevant arsenic compounds. The trivalent arsenicals, such as arsenite (AsIII) and its metabolites monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) are not easily detected using ESI-MS due to their poor ionizability, but they are known to have high affinity for thiols. Thus, the easily ionizable dithiol dimercaptosuccinic acid (DMSA) was used to derivatize the trivalent arsenicals prior to ESI-MS. Selection of the derivatizing reaction was based on studies of arsenic-thiol interactions. An HPLC-ESI-MS/MS method was developed for the detection of derivatized AsIII, DMAIII and MMAIII and underivatized arsenate (AsV), monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV), and was used to analyze multiple types of samples including urine, plasma and water. One set of groundwater samples from the site of a former pesticide manufacturing plant contained concentrations of MMAIII as high as 3.9-274 mg/L, the highest ever observed in the environment. Another HPLC-ESI-MS/MS method, without the need of derivatization, was developed for the detection of the toxic thio-arsenicals dimethylmonothioarsinic acid (DMMTAV) and monomethylmonothioarsonic acid (MMMTAV). DMMTAV was present in rat plasma and human urine and both DMMTAV and MMMTAV were detected in rat urine. The method of derivatization and ESI-MS/MS detection was extended to the speciation of inorganic SbIII and SbV. The use of the HPLC-ESI-MS/MS method using DMPS derivatization enabled the speciation of SbIII and SbV in water samples from mine waste.

Nano-ESI mass spectrometry is an attractive analytical technique due to its high sensitivity and small sample consumption, which is especially important for research areas such as proteomics. However, current nano-ESI emitters become a bottleneck for nano-ESI to be widely applied because of problems such as clogging, poor robustness, large flow resistance, and poor spray efficiency for highly aqueous solutions. The objective of this thesis study is to address the problems associated with tapered emitters and provide alternative solutions by developing advanced nano-ESI emitters. Two strategies that were explored to improve the clogging resistance and robustness while maintaining comparable electrospray performances include the development of emitters with larger apertures and multiple channels. Following these strategies, five types of emitters were fabricated without tapering either internal or external diameters, which include a roughened open tubular emitter, a porous membrane-assisted emitter, a microstructured multiple channel photonic crystal fiber (MSF) emitter, a packed ODS bead emitter, and an entrapped ODS bead emitter. The successful transformation of MSF fibers to nanoelectrospray emitters demonstrates a new practical approach to expand the application of nano-ESI because of its availability, compatibility, precisely controlled channel dimensions, variety of channel patterns, and feasibility for surface modification. The fundamental mechanism of non-tapered emitters was studied at nano flow rates. The fact that a plume of mist, instead of single Taylor cone, is generated from multiple channel emitters at nano flow rates suggests multiple Taylor cones may be formed. The calculated sensitivity gains from a MSF emitter compared to a single-tip tapered emitter are related to the number of the orifices containing on a MSF emitter. The characterization of impacts of operational parameters on nanoelectrospray performances shows that non-tapered emitters are more robust and less dependent on the emitter’s fine positioning. It was also found that unlike tapered emitters, non-tapered emitters can be positioned ten times further from the orifice of a mass spectrometer, which is greatly beneficial to online sample manipulation and purification. Furthermore, the electrospray efficiency of spraying highly aqueous solutions (e.g. 90%) was greatly improved through the hydrophobic modification of a MSF emitter exit. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-09-17 19:07:12.847

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Electricity supply industries (ESI) around the world are subject to structural and regulatory change. The environmental implications of these changes will depend, largely, on future investment within cleaner technologies. As developing countries (Des) increase levels of electricity supply, the incentives for investment in clean technologies is particularly important. Policy-makers wishing to promote renewable electricity technologies (RETs) in Des need to understand the nature of technological change in large technical systems (LTS). Broadly this thesis adopts the view that technological change is the outcome of the complex interaction of technical, economic and political factors. Initially technological change in LTS is shaped by social and political factors. As the system increases in both size and complexity driven by economies of scale and scope, and through co-evolution of technical and institutional features, it exhibits 'momentum,' whereupon technological change tends to be 'incremental' and autonomous. Through problem-solving activities to address 'reverse salients' the system evolves on a 'technological trajectory,' its path confined by technological and economic boundaries defined by the prevailing 'techno-economic' paradigm. Subsequently new technologies such as RETs, with characteristics different to those of the 'Traditional Electricity System Trajectory' (TEST) are unlikely to be favoured. Restructuring the electricity system provides a discontinuity in its momentum, allowing the drivers and interactions of different stakeholders to be more transparent. During such periods of instability there are important opportunities for systemic change through meaningful policy input. The socio-economic importance of electricity supply in Des further increases the 'technoinstitutional complexity' within the electricity system, and so resistance to restructuring. The thesis argues that restructuring of the ESI is a necessary, but not sufficient requirement for commercialisation of RETs. Rather policies supported by legislation should ensure that conservative techno-institutional mechanisms are replaced by ones that encourage a 'Balanced Electricity System Trajectory.' The BEST framework incorporates 'economies of the system' as a driver and is characterised by distributed technologies including small-scale and modular generation and sophisticated control technologies. As well as being characterised by flexible control in the technical sense, the BEST model is also characterised by flexible institutional arrangements.

Electrospray ionization mass spectrometry (ESI-MS) has been applied to the real time study of air-sensitive homogenous organometallic catalytic reactions due to its soft ionization properties. Therefore, fragile molecules and complexes in these reactions were characterized. The kinetic studies of these reactions have also been done by following the relative abundance of different species including starting material(s), products, by-product(s) as well as intermediates. Based on the results, reaction pathways and mechanisms were proposed and numerical models were built to accurately mimic the reactions under specific condition. In order to make the reactions detectable by ESI-MS, many charged ESI-MS friendly substrates were synthesized as tracking tags, including 1-allyl-1-(prop-2-yn-1-yl)piperidin-1-ium hexafluorophosphate(V), 1-allyl-1-(prop-2-yn-1-yl)pyrrolidin-1-ium hexafluorophosphate(V), (4-ethynylbenzyl)triphenylphosphonium hexafluorophosphate(V), hex-5-yn-1-yltriphenylphosphonium hexafluorophosphate(V) etc. The method for continuously monitoring water- and oxygen-sensitive reactions in real time named pressurized sample infusion (PSI) was developed, optimized and applied throughout all the projects in the thesis. These techniques were applied to detailed studies of the intramolecular Pauson-Khand reaction (PKR) with Co2CO8 under different temperatures. The kinetic study results gave the entropy and enthalpy of the reaction and evidence suggested that the ligand dissociation step was the rate-determining step of the reaction. Hydrogenation of alkynes with Wilkinson’s catalyst and Weller’s catalyst were also studied using PSI. The behaviour of starting materials and products were tracked, then various reactions were carried out by using different temperatures and concentrations. Furthermore, competition reaction and kinetic isotope effect study, mechanisms were proposed based on experimental results, numerical models were built, and rate constants for each step were estimated. Different Si-H activation reactions were studied including hydrolysis of silanes, hydrosilation, dehydrocoupling of silanes, alcoholysis of silane and silane redistribution by using (3-(methylsilyl)propyl)triphenylphosphonium hexafluorophosphate(V). A variety of collaborative projects were also carried out including hydroacylation, fast-activating Pd catalyst precursor, catalyst analysis for Cu-mediated fluorination, CdSe - NiDHLA analysis, Ru catalyzed propargylic amination reaction, Zn catalyzed lactide polymerization, and Fe4S4 clusters. / Graduate / jingwei@uvic.ca