No description available.

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No description available.

This thesis explores three rare synthetic routes: the synthesis of hydrazines via the aza-Lossen rearrangement, the synthesis of carbamoyl azides from amines, and deprotection reactions using water at elevated temperatures. The aza-Lossen reaction was found to be ideal at “infinite dilution” conditions and could be performed with both aryl and alkyl example. Carbamoyl azides could be synthesized in high yields from both aryl and alkyl amines. The carbamoyl azide reaction was found to be much more efficient with Cs (+1) present. Lastly, water at elevated temperatures conditions was efficient at removing various amine and hydroxyl protecting groups.

We aimed to identify the volatile compounds in inflorescences of Rudbeckia hirta that may be responsible for the olfactory attraction of the crab spider Misumenoides formosipes to this plant. Our approach was to use ultrasonic extraction, separate the extract into fractions using flash chromatography with different solvent systems, and test the attraction of the male spiders to the pooled fractions using a y-tube olfactometer. Ultrasonic extraction is carried out using a mixture of 1:2 hexane/diethyl ether with 10 g of inflorescences for 30 minutes. Bioassay results indicated that male spiders chose the inflorescences, bulk ultrasonic extract, and the pooled 100% dichloromethane fractions over controls. Nuclear magnetic resonance experiments and infrared spectroscopy experiments were carried out on the 100% dichloromethane fractions and these experiments indicated that a long chain hydrocarbon is the main component in the 100% dichloromethane fractions / Chromatographic method and bioassay development method -- M. formosipes olfactory response to R. hirta -- Separation and identification of the possible attractants in the 100% dichloromethane fractions. / Department of Chemistry

Volatile organic compounds (VOCs) are emitted into the atmosphere from biogenic and anthropogenic sources with atmospheric lifetimes ranging from minutes to months, depending on the specific VOC compound considered. It is estimated that biogenic VOCs (BVOCs) (e.g. isoprenes, terpenes) make up 90% of the global atmospheric VOC budget. However, in highly industrialised regions, anthropogenic VOCs (e.g. benzene, toluene, ethylbenzene and xylene, combined abbreviated as BTEX) might dominate. VOCs have various reversible and irreversible effects on human health. They also have environmental impacts that range from changes in the population of terrestrial and aquatic ecosystems to the extinction of vulnerable species. VOCs are precursors for the formation of ozone (O3) during solar radiation initiated reactions in the presence of NOx. Tropospheric O3 is considered a pollutant, with negative impacts on human health, ecosystems and food security. O3 is also a short-lived greenhouse gas. Through reactions with radical species, VOCs lead to the formation of higher molecular weight organic compounds, which produce carbon monoxide (CO), peroxyacytyl nitrate (PAN) and ultimately secondary organic aerosol (SOA) particles. SOA particles impact directly on air quality and visibility, as well as directly and indirectly on the radiation balance of the earth that contributes to the regulation of climate. Notwithstanding the importance of atmospheric VOCs, limited data is available for VOCs in South Africa. In this study, a comprehensive dataset of BVOC and anthropogenic VOC species was obtained at the Welgegund measurement station in the North West Province, South Africa. Measurements were conducted from 9 February 2011 to 4 February 2012. Samples were collected on Tenax-TA and Carbopack-B adsorption tubes twice a week for two hours during day time and two hours during night time. The first 1.25m of the stainless steel sampling inlet was heated to 120ºC to remove O3 that could lead to sample degradation. Analyses of the sampled adsorption tubes were conducted by thermal desorption, cryofocusing, re-desorption, followed by gas chromatography separation and analysis with a mass selective detector (GC-MS). The results indicated that toluene was the most abundant aromatic hydrocarbon and heptane the most abundant alkane. Benzene is currently the only VOC listed as a criteria pollutant in the South African Air Quality Act with an annual average standard of 1.6ppb. The annual median benzene concentration was 0.13 ppb, while the highest daily benzene concentration measured was 8.7 ppb. No distinct seasonal cycles were identified for anthropogenic VOC species measured, i.e. aromatic hydrocarbons and alkanes. However, air mass history analysis indicated that air masses that passed over the Mpumalanga Highveld, the Vaal Triangle and the Johannesburg-Pretoria conurbation (collectively referred to as Area I) had significantly higher concentrations of these anthropogenic VOCs compared to air masses that passed over the western and eastern Bushveld Igneous Complex, and a region over which air masses typically followed an anti-cyclonic movement pattern (collectively referred to as Area II). Anthropogenic VOC levels in air masses that passed over the regional background (areas with no large point sources) had levels similar to air masses that had passed over Area II. Relatively good interspecies correlations (r > 0.8) between most of the aromatic hydrocarbons in air masses that had passed over Area I, with the exception of benzene, indicated that these species had common sources. Benzene, however, correlated well with CO, indicating that sources associated with incomplete combustion were most likely the origin of benzene in air masses that had passed over Area I. The interspecies concentration ratios for plumes passing over Area I indicated that this source region is relatively close to the Welgegund monitoring station and air masses that passed over this source region were substantially influenced by anthropogenic activities. The concentration ratios for plumes that passed over Area II and the Regional Background indicated that these were aged air masses. Furthermore, the concentration ratios of toluene, ethylbenzene and o,m,p-xylene (TEX) to the total aromatic concentration for air masses that passed over the various source regions showed a greater contribution to the total VOC concentration during periods of higher temperature, i.e. summer. This proved that the evaporation of solvents contributes significantly to VOC levels during the months with higher temperatures. The relative contribution of aromatic hydrocarbons to photochemical O3 formation in air masses that passed over the various source regions indicated the highest contribution was observed for air masses that passed over Area I, with Area II and the Regional Background in the same order of magnitude. The annual temporal variations of the measured BVOCs indicated that 2-methyl-3-buten-2-ol (MBO) and isoprene exhibited distinct seasonal patterns, i.e. higher values in summer and lower values in winter. The monoterpenes (MT) and the sesquiterpenes (SQT) did not follow distinct seasonal patterns. BVOC concentrations correlated relatively well to seasonal variations in temperature, photosynthetically active radiation (PAR), rainfall, relative humidity (RH) and CO2 flux. This proved that biogenic activity is responsible for BVOCs emitted. The most abundant MT was -pinene, while -caryophyllene was the most abundant SQT with annual median concentrations of 0.468 ppb and 0.022 ppb, respectively. Pollution roses for isoprene showed a dominance of sources from the north-west to the north-east, as well as the south-east. These directions correlated to areas where pockets of the savannah biome are located. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

Volatile organic compounds (VOCs) are emitted into the atmosphere from biogenic and anthropogenic sources with atmospheric lifetimes ranging from minutes to months, depending on the specific VOC compound considered. It is estimated that biogenic VOCs (BVOCs) (e.g. isoprenes, terpenes) make up 90% of the global atmospheric VOC budget. However, in highly industrialised regions, anthropogenic VOCs (e.g. benzene, toluene, ethylbenzene and xylene, combined abbreviated as BTEX) might dominate. VOCs have various reversible and irreversible effects on human health. They also have environmental impacts that range from changes in the population of terrestrial and aquatic ecosystems to the extinction of vulnerable species. VOCs are precursors for the formation of ozone (O3) during solar radiation initiated reactions in the presence of NOx. Tropospheric O3 is considered a pollutant, with negative impacts on human health, ecosystems and food security. O3 is also a short-lived greenhouse gas. Through reactions with radical species, VOCs lead to the formation of higher molecular weight organic compounds, which produce carbon monoxide (CO), peroxyacytyl nitrate (PAN) and ultimately secondary organic aerosol (SOA) particles. SOA particles impact directly on air quality and visibility, as well as directly and indirectly on the radiation balance of the earth that contributes to the regulation of climate. Notwithstanding the importance of atmospheric VOCs, limited data is available for VOCs in South Africa. In this study, a comprehensive dataset of BVOC and anthropogenic VOC species was obtained at the Welgegund measurement station in the North West Province, South Africa. Measurements were conducted from 9 February 2011 to 4 February 2012. Samples were collected on Tenax-TA and Carbopack-B adsorption tubes twice a week for two hours during day time and two hours during night time. The first 1.25m of the stainless steel sampling inlet was heated to 120ºC to remove O3 that could lead to sample degradation. Analyses of the sampled adsorption tubes were conducted by thermal desorption, cryofocusing, re-desorption, followed by gas chromatography separation and analysis with a mass selective detector (GC-MS). The results indicated that toluene was the most abundant aromatic hydrocarbon and heptane the most abundant alkane. Benzene is currently the only VOC listed as a criteria pollutant in the South African Air Quality Act with an annual average standard of 1.6ppb. The annual median benzene concentration was 0.13 ppb, while the highest daily benzene concentration measured was 8.7 ppb. No distinct seasonal cycles were identified for anthropogenic VOC species measured, i.e. aromatic hydrocarbons and alkanes. However, air mass history analysis indicated that air masses that passed over the Mpumalanga Highveld, the Vaal Triangle and the Johannesburg-Pretoria conurbation (collectively referred to as Area I) had significantly higher concentrations of these anthropogenic VOCs compared to air masses that passed over the western and eastern Bushveld Igneous Complex, and a region over which air masses typically followed an anti-cyclonic movement pattern (collectively referred to as Area II). Anthropogenic VOC levels in air masses that passed over the regional background (areas with no large point sources) had levels similar to air masses that had passed over Area II. Relatively good interspecies correlations (r > 0.8) between most of the aromatic hydrocarbons in air masses that had passed over Area I, with the exception of benzene, indicated that these species had common sources. Benzene, however, correlated well with CO, indicating that sources associated with incomplete combustion were most likely the origin of benzene in air masses that had passed over Area I. The interspecies concentration ratios for plumes passing over Area I indicated that this source region is relatively close to the Welgegund monitoring station and air masses that passed over this source region were substantially influenced by anthropogenic activities. The concentration ratios for plumes that passed over Area II and the Regional Background indicated that these were aged air masses. Furthermore, the concentration ratios of toluene, ethylbenzene and o,m,p-xylene (TEX) to the total aromatic concentration for air masses that passed over the various source regions showed a greater contribution to the total VOC concentration during periods of higher temperature, i.e. summer. This proved that the evaporation of solvents contributes significantly to VOC levels during the months with higher temperatures. The relative contribution of aromatic hydrocarbons to photochemical O3 formation in air masses that passed over the various source regions indicated the highest contribution was observed for air masses that passed over Area I, with Area II and the Regional Background in the same order of magnitude. The annual temporal variations of the measured BVOCs indicated that 2-methyl-3-buten-2-ol (MBO) and isoprene exhibited distinct seasonal patterns, i.e. higher values in summer and lower values in winter. The monoterpenes (MT) and the sesquiterpenes (SQT) did not follow distinct seasonal patterns. BVOC concentrations correlated relatively well to seasonal variations in temperature, photosynthetically active radiation (PAR), rainfall, relative humidity (RH) and CO2 flux. This proved that biogenic activity is responsible for BVOCs emitted. The most abundant MT was -pinene, while -caryophyllene was the most abundant SQT with annual median concentrations of 0.468 ppb and 0.022 ppb, respectively. Pollution roses for isoprene showed a dominance of sources from the north-west to the north-east, as well as the south-east. These directions correlated to areas where pockets of the savannah biome are located. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

Xenobiotic Organic Compounds (XOCs) are present in wastewater and wastewater-impacted environmental systems. Pharmaceuticals and personal care products are a broad and varied category of chemicals that are included among these compounds. Although, these compounds have been detected at low levels in surface water, concerns that these compounds may have an impact on human health and aquatic life, have led to increased interest in how XOCs are removed during wastewater treatment. Recognizing specific mechanisms in recent literature and simulating those mechanisms responsible for the removal of XOCs is the main objective of this study. Conventional models, such as the popular activated sludge models (ASM1, ASM2, etc), do not sufficiently address the removal processes; therefore, a fate model is created to provide a means of predicting and simulating removal mechanisms along with experimental analyses. GPS-X is a multi-purpose modeling tool for the simulation of municipal and industrial wastewater treatment plants. This software package includes conventional models as built-in libraries, which can be used as bases on which new models can be created. In this thesis, the removal mechanisms of XOCs are recognized and investigated; a new library for GPS-X is also created to include XOCs. As a first step the uncalibrated fate model, which includes all mechanisms of interest with their process rates and state variables, is developed using in GPS-X software. A modified ASM1 (Mantis model) is used as a basis for developing the fate model. Since only a group of mechanisms is responsible for the removal of each compound the mechanisms are categorized in three different case studies as the next step. Thus, one submodel is associated with each case study. The model developer toolbar in GPS-X software is used to develop the model for these case studies. The first case study involves the removal of antibiotics, such as Sulfamethoxazole. The removal mechanisms used in this case are biodegradation, sorption, and parent compound formation, with co-metabolism and competitive inhibition effects being inserted into the structure of the model. Secondly, the removal of nonylphenol ethoxylates (NPEOs) occurs through abiotic oxidative cleavage, hydrolysis, and biodegradation. The third case study includes removal mechanisms of biodegradation and sorption for neutral and ionized compounds. In the calibration process, model parameters are tuned such that the model can best simulate the experimental data using optimization methods. A common error criterion is Sum of Squared Errors (SSE) between the simulated results and the measured data. By minimizing SSE, optimal values of parameters of interest can be estimated. In each case study different data sets were used for the validation process. To validate the calibrated model, simulated results are compared against experimental data in each case study. The experimental data set used in the validation process is different from that used for calibrating the model, which means the validation process data set was obtained from the different literature. By looking at the validation results, it is concluded that the proposed model successfully simulates removal of XOCs. Since the operating parameters of wastewater treatment plants, such as Solids Retention Time (SRT) and Hydraulic Retention Time (HRT) are crucial for the fate of XOC???s, a sensitivity analysis is carried out to investigate the effect of those parameters. Moreover, the pH effect is studied because it relates to the ionized XOCs. Sensitivity analysis results show that the fate model is more sensitive to model parameters i.e. biodegradation rate constant (kb) than the operational parameters, i.e. SRT and HRT. Furthermore, the responses showed sensitivity to pH, whereby acidic conditions provide a better environment for removing neutral forms and alkaline conditions were suitable for removing ionized forms, according to the ionized compound fate model.

Detecting the presence of insects at low densities can avoid total deterioration of stored grains because corrective actions can be implemented early. Tribolium castaneum (Herbst) and Cryptolestes ferrugineus (Stephens) are the major insect pests of the Canadian grain handling industry. Identification of the volatile organic compounds released by insects can be used to detect insects in stored grains. An attempt was made to identify the volatile organic compounds released by T. castaneum and C. ferrugineus by headspace analysis. The volatiles in the head space of vials with insects, insects and wheat flour, and insects and wheat, were analyzed using a GC-MS coupled with an automatic headspace sampler. Wheat with fifteen percent moisture content was used in this study along with two different insect densities. Feasibility of the automatic headspace sampler in headspace analysis was found to be positive. The sampler can do sample conditioning, absorption, trap cleaning and desorption of the volatiles into the GC-MS and speed up the process. The samples extracted at 20 strokes with 1000 µL per stroke, and desorbed at 250°C gave a clear peak of compounds. The amount of volatiles produced by T. castaneum adults varied based on insect densities, the concentration of Methyl-1, 4-benzoquinone; Ethyl-1, 4-benzoquinone; and 1-Tridecene released by ten adult insects were 355, 390 and 530 µg/L compared to 300,310 and 210 µg/L of Methyl-1, 4-benzoquinone; Ethyl-1, 4-benzoquinone; and 1-Tridecene produced by five adult insects. Extreme high and low temperature leading to death produced very high amounts of volatiles compared to insects kept at 35°C. The larvae of the T. castaneum insects did not produce any volatiles at ambient condition as well as at extreme cold and warm conditions. The C. ferrugineus adults did not produced any detectable amount of volatiles even at the higher insect density after up to 3 days. The results of the combination of T. castaneum and C. ferrugineus insects gave the same volatile organic compounds as produced by T. castaneum insects alone. The 1-Tridecene produced by T. castaneum was not reported previously in other studies.

A series of para-dioxolene bridging ligands with bis-tridentate or bis-bidentate coordination pockets have been prepared. These ligands were designed to serve as building blocks in the preparation of functional metallosupramolecular structures. The bis-tridentate dipyridyl-diazaanthraquinones have topologies suitable for the preparation of [2 x 2] grids or larger extended structures. Employing a double condensation reaction between 1,3-diamino-4,6-benzenedicarboxaldehyde and 2-acetyl pyridine successfully afforded a cisoid binding diazaanthraquinone. The redox activity of the latter revealed it is more easily reduced than structurally similar 1,5- and 1,8-diazaanthraquinones. The synthesis of an analogous ligand displaying transoid coordination pockets proved challenging. Several approaches were attempted however the preparation of key intermediates 1,4-dinitro-2,5-benzenedicarboxaldehyde and 2,5-diamino-1,4-(hydroxyI-methyl) benzene were unsuccessful. A collection of bis-bidentate 2,5-bis(phosphino)1,4-dioxolenes were prepared with diphenyl, diisopropyl and diethoxy substituents at the phosphorus center. 2,5- Dibromo-1,4-dimethoxybenzene was reacted with the appropriate chlorophosphine under lithiation conditions to afford the dimethoxy compound, which was subsequently deprotected to the hydroquinone state with a Lewis acid. The diphenylphosphino hydroquinone was oxidized using phenyliodonium bisacetate, however efforts to oxidize other hydroquinone precursors to the targeted quinone state proved challenging. Diphenyl and diisopropyl phosphino hydroquinones were successfully coordinated with diamagnetic palladium hexafluoroacetylacetonate precursors. The resulting bimetallic bis(phosphino) dianion complexes were subsequently oxidized to the semiquinone state using silver (I) hexafluorophosphate and studied to determine the distinctive features of the semiquinone ligand.