Thesis (M.Sc.)--York University, 2006. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 89-97). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19645

Allylic substitution is an important procedure for carbon-carbon, carbon-nitrogen and carbon-oxygen bond formation, and palladium-mediated allylic substitution reactions have previously been employed in the synthesis of a range a physiologically active and natural products. 2,5-Dicarbon substituted 2,5-dihydrofurans have not to date been synthesised by palladium-mediated allylic substitution reactions. It was found in the first part of the work that allylic substitution reactions of 2,5-diacetoxy-2,5-dihydrofuran with a tertiary carbon nucleophile did not result in the desired mono-substitution product due to the elimination of acetic acid from the product, to form the aromatised furan derivative. In an attempt to differentiate between the two potential leaving groups on the dihydrofuran, one of the acetate groups was displaced in a palladium-mediated allylic substitution reaction. This approach was also intended to inhibit the aromatisation reaction. The desired product 2-acetoxy-5-phenoxy-2,5-dihydofuran was obtained. The palladium-mediated allylic substitution reactions of this product with a range of tertiary carbon nucleophiles provided the desired mono-substituted dihydrofuran products in good yield with minimal by-products being detected. The substitution of the phenoxy-leaving group with a carbon nucleophile, however, was not achieved under a range of reaction conditions. Other more electrondeficient phenol derivatives were used in the initial substitution reactions but due to time constraints the work could not be completed in the current study. This would hopefully have increased the leaving group ability of the phenoxy group and the desired disubstituted dihydrofuran would have been achieved, and this will be the subject of further work in this regard. Milder reaction conditions were applied to 2,5-diacetoxy-2,5-dihydrofuran in its reaction with a tertiary carbon nucleophile. The desired mono-substituted mono acetoxy products were obtained in reasonable yields when column chromatography was performed at –15 °C and the silica was neutralised with Et3N. These mono-acetoxy products were reacted with a range of tertiary carbon nucleophiles and the desired disubstituted dihydrofurans could be prepared in reasonable yields. One-pot reactions were investigated by using three equivalents of nucleophile and in most cases the desired symmetrical dihydrofuran was achieved. This result prompted the investigation into the synthesis of disubstituted dihydrofurans in a one-pot reaction by successive addition of two carbon nucleophiles with 2,5- diacetoxy-2,5-dihydrofuran. The disubstituted dihydrofurans were isolated in higher yields than the two-pot procedure and the complex purification procedure developed was not necessary. This study, therefore, allowed for the synthesis of a range of symmetrical and unsymmetrical dicarbon substituted dihydrofurans. This methodology will later be applied to the synthesis of a range of natural products. / Prof. D.B.G. Williams

Adsorption combined with aqueous phase electrochemical regeneration has been shown by researchers at The University of Manchester (UoM) to offer an alternative approach to the removal of organics from waters and wastewater's. The process, based on a regenerable graphite intercalation compound (GIC) adsorbent, produces no secondary waste, is energy efficient and chemical free. A company, Arvia Technology Ltd., was set up in 2007 to commercialise the technology. As part of a growth and development strategy Arvia investigated other possible applications of the technology and found that odour removal from gas streams might be a good fit with technology features. This Engineering Doctorate (EngD) was a direct investigation into both this technology fit and into the market opportunity for technologies treating odours and volatile organic compounds (VOCs) in gas streams. The research conducted demonstrated that the technology in its different applied forms had certain process drawbacks. Where mass transfer, adsorption and regeneration were combined in a single unit, enhanced transfer as a result of higher pollutant Henry's coefficient was offset by lower adsorbate affinity which varied with hydrophobicity. This relation between affinity and hydrophobicity was different for oxygen functionalised aromatic molecules than for the aliphatic molecules studied. Where adsorption occurred in the gaseous phase and regeneration in the aqueous phase, disadvantages such as short adsorbent packed bed lifetimes and lower current efficiencies of oxidation as a result of adsorbate desorption were shown to be an issue. When the above process challenges were set against the challenging market environment and relatively small market opportunity (approx. £52 million in Europe, 2012) it was difficult to recommend further broad research into the technology. However it was concluded that the concept might still be usefully applied to odour and VOC abatement and that further work should focus on a two phase system with a gas phase adsorbent regeneration technique. The relation observed between adsorbate affinity, hydrophobicity and structure allowed the demonstration of the preferential removal of phenol from solutions containing significantly higher concentrations of aliphatic molecules. This finding is considered the most important project output as it highlights an opportunity to develop Arvia's water treatment technology into a targeted water treatment system for the removal of specific, industrially important, organic contaminants.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Ethylene (C₂H₄) production was monitored in twelve desert soils incubated moist at constant temperature for various incubation periods. In all but two soils with high organic matter content, C₂H₄ production was low. Statistical analysis showed a good correlation between organic matter content and C₂H₄ production. Minimum levels of C₂H₄ were observed in saline and sodic soils. Adding ethanol, glucose, glycerol and methionine to soil samples significantly increased C₂H₄ formation. Methionine induced the highest level of C₂H₄ in all soils tested. Increased concentrations of methionine resulted in further significant increases in C₂H₄ production possibly indicating its role as a precursor for C₂H₄. Chloramphenicol did not have a significant effect except in a saline soil suggesting that bacterial C₂H₄ production is of less significance in the other soils. The addition of salts to the high C₂H₄ producing soils suppressed C₂H₄ production most likely because of a direct effect on C₂H₄ producing microorganisms through toxic salt levels, high osmotic pressure and/or increased pH. Leaching of four saline soils and subsequent incubation resulted in significant increases in C₂H₄ in two soils. Ethylene producers, previously inhibited by salinity, were probably reactivated when the salts were removed. A Fusarium isolate obtained from the highest C₂H₄ producing soil, produced the most C₂H₄ in pure culture followed by isolates belonging to the genera Aspergillus, Penicillium, Curvillaria, and Rhizopus. In a comparative study, a number of species, some of which were known to produce C₂H₄, were tested in culture media. Nine species produced C₂H₄ in varying amounts of which Penicillium digitatum produced the highest concentration. A sterilized saline soil produced significant C₂H₄ when inoculated with spores of Mucor hiemalis and the Fusarium isolate, 5 to 14 times that in non-sterilized soil probably indicating an originally low population of C₂H₄ producing organisms. The amounts of C₂H₄ produced in sterilized inoculated mollisol and garden soils were only a fraction of that produced in non-sterilized samples probably indicating the involvement of a number of species in the production of C₂H₄ in these soils.

The sorption of five chlorinated benzenes and sixteen other organic solutes was investigated by determining the extent of sorption and the sorption rates in a series of 40 batch and 139 column experiments using surface-modified silica of known chemical composition. These surfaces were used to represent important functional groups in soil, and consisted of porous silica with patchy surface coatings of aliphatic chains (C₁, C₈, and C₁₈), and other substituent groups (phenyl, amine, alcoholic, and carboxylic). Three possible rate-limiting steps were examined: diffusion through immobile pore fluid, diffusion through bound organic matter, and the chemical binding and release rate. First-order desorption rate coefficients were observed to be 10⁻¹ to 10⁻² s⁻¹ on unbonded, and C₈, C₁₈, amine, and alcoholic modified surfaces, and 10⁻³ to 10⁻⁵ s⁻¹ on C₁ and phenyl-polymer modified surfaces. Diffusion through immobile pore fluid had only a minor effect on the sorption rate, as evidenced by similar rates on organic-bound porous and solid particles. The diffusion rate through the bound organic layer is not rate limiting due to the small organic layer thickness. The observed slow desorption on the phenyl-polymer surface is consistent with the rate limiting step being the chemical binding and release rate. The changes in the rate with temperature and within a series of chlorinated benzenes support this conclusion. The free energies for sorption onto the phenyl-polymer surface ranged from -4.0 kcal mol⁻¹ for chlorobenzene to -6.9 kcal mol⁻¹ for pentachlorobenzene, which are within the range expected for van der Waals interactions. The observed sorption energies are slightly stronger than predicted for hydrophobic surfaces, possibly reflecting strong binding due to multiple pi-pi electron interactions on the phenyl-polymer surface. Hydrophobic solute partitioning onto natural soils, as observed by others, is less than that observed on aliphatic and phenyl hydrophobic surfaces in this study, but greater than on amine or alcoholic modified surfaces. The sorption of di-, tri-, and tetra-chlorobenzenes onto the phenyl-polymer surface is apparently driven by the overall sorption enthalpy (ΔH° = -3.9 to -4.9 kcal mo1⁻¹) and to a lesser extent by the entropy (TΔS° = 0.5 to 1.5 kcal mol⁻¹). As equilibrium of the reactions observed in this study are reached within hours, these reactions are important at small field scales where residence times are hundreds of hours or less.

Helium tracer experiments were conducted to characterize conservative tracer behavior in a wedge-shaped lysimeter containing alternating layers of unsaturated silty sand, and clay loam. Experiments were conducted with trichloroethylene and 1,1,1-trichloroethane to determine if air stripping in unsaturated soil could be characterized by mass transfer from the sorbed to the liquid to the vapor phase. Batch experiments were conducted to measure liquid--vapor mass transfer. Solid-liquid-vapor mass transfer was characterized by measuring the vapor phase re-equilibration after the air stripping experiment. The Discrete State Compartment model was used to simulate a conservative gas tracer. The results were compared to the helium tracer. Liquid-vapor, and solid-liquid-vapor mass transfer were modeled by fitting simulated data to experimental data. The conservative tracer, and mass transfer models were combined to simulate air stripping in unsaturated soil.

Dissolved organic matter (DOM) is the most dynamic and least understood part of the global oceanic carbon cycle. Furthermore the molecular composition of DOM is largely unknown. This study focused on the distribution pattern, removal processes and molecular characterisation of DOM in a range of estuaries and coastal zones in New Zealand. Doubtful Sound, the longest fjord in Fiordland National Park, South Island, New Zealand was of particular interest, because of the combination of extreme rainfall, enhanced production of DOM within the temperate rainforest which largely appears in the relatively deep ([greater than or equal to] 5 m) low salinity layer (LSL) at the fjord surface. A typical river estuary (Freshwater River) located in Stewart Island, New Zealand was also investigated. Optical water properties such as the UV/Vis absorption coefficient at 355 nm (a[CDOM](355)) and excitation-emission matrix fluorescence (EEM) were determined for samples from freshwater, across the LSL into open ocean water. These optical properties showed a marked decrease with salinity and highest levels of EEM fluorescence and a[CDOM] (355) in the brackish surface water. In addition to the observed changes in the optical properties, ultrahigh resolution Electrospray Ionisation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS) determination of molecular formulae revealed that in the fjord about 20 % of these formulae changed along a vertical salinity gradient across the LSL between the brackish surface water and the saline water at 5 m depth. This trend was even more pronounced along the salinity gradient of the Fresh Water River Estuary in Stewart Island, where 60 % of all assigned molecular masses changed from freshwater over the mixing zone to ocean water. Associated with these changes was a marked increase in aromaticity with increasing salinity. Comparable behaviour with increasing salinity was also observed in estuarine samples from the Cape Fear River system, North Carolina, USA. In contrast, only minor changes were determined in molecular formulae for surface water samples collected along a transect off the Otago Coast and across the Subtropical Convergence (STC) into Subantarctic Water (SAW). However, a comparison of the molecular formulae assigned to the DOM pool for the STC water and a freshwater stream in Doubtful Sound, revealed that 75 % of all the assigned formulae for the open ocean sample were common to these two markedly different types of natural waters. This seemingly refractory DOM contained nearly 600 assigned molecular formulae, which were all very similar (only spaced by two hydrogen and CH₂ groups) and could be explained with only 9 general molecular formulae. However, the comparison of all assigned formulae for the freshwater sample suggested that about 90 % of the assigned molecular formulae for the terrestrially-derived DOM changed as it moved from rivers to the open ocean and that only 10 % remained the same. Singlet oxygen showed a very close relationship with the optical properties such as the absorption coefficients (a[CDOM](355)) and the EEM fluorescence intensities and these results suggested that singlet oxygen steady state concentrations are linked to CDOM. Photodegradation processes were confirmed to be responsible for a significant destruction of CDOM. Samples collected from different salinity waters showed major differences in wavelength-dependent photo-decay of CDOM suggesting that the rate of photodegradation in the UV range decreased with increase in salinity whereas it was enhanced for longer wavelength radiation ([greater than or equal to]400 nm). Additionally, the predominantly unsaturated compounds produced during estuarine mixing were found to be highly photolabile and were either destroyed or new unsaturated compounds were produced within 21 h of solar irradiation.

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