Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Water resources in South Africa are scarce, and should therefore be protected against pollutants, also from persistent organic pollutants (POPs). This is emphasised by the Stockholm Convention on POPs, which aims at reducing and ultimately eliminating POPs. South Africa signed and ratified the treaty, and it became international law on 17 May 2004. POPS are highly stable, toxic, hydrophobic and lipophilic compounds, with the ability to accumulate in biological tissues. Previous research had shown that dioxin-like POPS are present in the aquatic environments of South Africa, with the highest concentrations of these substances measured in industrialised areas of South Africa. The present study aimed at investigating the extent of polychlorinated dibenzo-para-dioxin (PCDD), polychlorinated dibenzo-furan (PCDF) and polychlorinated biphenyl (PCB) pollution in the Vaal Triangle, by targeting aquatic sediments and biota. Sediment samples were collected from the Blesbok Spruit, Taaibos Spruit, Leeu Spruit and Suikerbosrand River, and fish tissue samples were collected from Blesbok Spruit and Suikerbosrand River, to determine bio-accumulation. The samples were extracted with organic solvents, cleaned-up and fractionated. Raw extracts and fractions were analysed with the H4IIE-luc reporter gene bio-assay. This bio-assay is a rapid, sensitive and relatively cost-effective method, which measures the effects of dioxin-like compounds on rat hepatoma cells, transfected with firefly luciferase gene. Selected samples were analysed with gas chromatographylmass spectrometry (GCIMS) to confirm results. Only one site had quantifiable amounts of dioxin-like substances in the sediment, measured to be 52.35 ng/kg [Effective Concentration 50 (EC 50)]. This value exceeds many of the European and USA quality guidelines, proposed for sediments. No dioxin-like substances were found in fish tissues. The absence of PCDD/Fs and PCBs in aquatic sediments and fish tissues from the Vaal Triangle area might be due to the climatic conditions of the area, dilution effects in streams, and degradation of these compounds by UV-radiation and microbial organisms. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Water resources in South Africa are scarce, and should therefore be protected against pollutants, also from persistent organic pollutants (POPs). This is emphasised by the Stockholm Convention on POPs, which aims at reducing and ultimately eliminating POPs. South Africa signed and ratified the treaty, and it became international law on 17 May 2004. POPS are highly stable, toxic, hydrophobic and lipophilic compounds, with the ability to accumulate in biological tissues. Previous research had shown that dioxin-like POPS are present in the aquatic environments of South Africa, with the highest concentrations of these substances measured in industrialised areas of South Africa. The present study aimed at investigating the extent of polychlorinated dibenzo-para-dioxin (PCDD), polychlorinated dibenzo-furan (PCDF) and polychlorinated biphenyl (PCB) pollution in the Vaal Triangle, by targeting aquatic sediments and biota. Sediment samples were collected from the Blesbok Spruit, Taaibos Spruit, Leeu Spruit and Suikerbosrand River, and fish tissue samples were collected from Blesbok Spruit and Suikerbosrand River, to determine bio-accumulation. The samples were extracted with organic solvents, cleaned-up and fractionated. Raw extracts and fractions were analysed with the H4IIE-luc reporter gene bio-assay. This bio-assay is a rapid, sensitive and relatively cost-effective method, which measures the effects of dioxin-like compounds on rat hepatoma cells, transfected with firefly luciferase gene. Selected samples were analysed with gas chromatographylmass spectrometry (GCIMS) to confirm results. Only one site had quantifiable amounts of dioxin-like substances in the sediment, measured to be 52.35 ng/kg [Effective Concentration 50 (EC 50)]. This value exceeds many of the European and USA quality guidelines, proposed for sediments. No dioxin-like substances were found in fish tissues. The absence of PCDD/Fs and PCBs in aquatic sediments and fish tissues from the Vaal Triangle area might be due to the climatic conditions of the area, dilution effects in streams, and degradation of these compounds by UV-radiation and microbial organisms. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

De nos jours, l’industrie chimique est de plus en plus confrontée à la question de son impact environnemental. Dans le même temps, elle doit faire face à la diminution des ressources de matières premières importantes tels que les métaux de transition, tout en respectant des contraintes économiques. Ces travaux de thèse avaient pour but de tenter de répondre à ces exigences, par le développement de méthodologies de synthèse basées sur l’utilisation de catalyseurs hétérogènes recyclables. En combinant les propriétés catalytiques de certains ions métalliques avec les propriétés de catalyseurs solides tels que les polyoxométallates ou les zéolithes, nous avons pu mettre au point de nouveaux outils pour la synthèse organique. Les polyoxométallates dopés à l’argent ont démontré leur efficacité dans le réarrangement d’alcynyloxiranes en furanes. La synthèse de spiroacétals et d’acétals par dihydroalkoxylation d’alcyne diols a été effectuée pour la première fois en catalyse à l’argent, via l’utilisation de zéolithes. En perspective, nous avons mis en évidence les applications potentielles de ces procédés verts dans la synthèse totale de molécules plus complexes. Les premiers résultats suggèrent que de telles synthèses plus respectueuses de l’environnement ont tout intérêt à être davantage utilisées à l’avenir. / Nowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future.

No description available.

Les dioxines/furanes sont des polluants organiques persistants générés principalement par l’activité anthropique et spécifiquement par l’industrie lors des procédés de combustion mettant en jeux des matières organochlorées. Etant donné leur transport à large échelle dans l'environnement et leur impact sur la santé de l’homme, il est nécessaire de contrôler en temps réel, les traces de dioxines à l'émission des sources fixes. Un tel contrôle est plus particulièrement requis lors de l’incinération de déchets hétérogènes non préalablement triés. Deux types de matériaux microporeux ont été sélectionnés pour l'adsorption des dioxines au vu de leurs propriétés physico-chimiques. Il s’agit des zéolithes et les Metal-Organic Frameworks (MOF). Deux types de test d’adsorption ont été conduits, d’une part, en laboratoire en phase liquide avec la dioxine dans de l’isooctane comme solvant, et d’autre part, en phase gazeuse lors des campagnes de prélèvement sur un site d'incinération de déchets avec une matrice réelle très complexe. L'adsorption en phase liquide nous a permis de conclure sur l’efficacité des matériaux étudiés pour l’adsorption de trois congénères de dioxine de différentes tailles. Elle a ensuite été caractérisée par des techniques d'analyses spécifiques afin de remonter aux mécanismes d'adsorption. L’efficacité d’adsorption a été testée en phase gaz sur un site d'incinération de déchets ménagers avec les mêmes matériaux testés en phase liquide au laboratoire. Finalement, en se basant sur les résultats d'adsorption en phases liquide et gaz, deux pistes ont été proposées pour la conception d’un dispositif de mesure de dioxines en ligne commercialisable. / Dioxins and furans are persistent organic pollutants generated mainly by human activity and industry during combustion processes using organochlorine substances. Due to their long-range air transport and impact on human health, it is necessary to have on-line dioxin emission monitoring at stationary source. Such a control is tipically required for incineration of no pre-sorted heterogeneous wastes.Two types of microporous materials have been selected for dioxin adsorption due to their physicochemical properties: zeolites and Metal -Organic Frameworks (MOF). Two types of adsorption tests have been established. On the one hand, dioxin adsorption tests in liquid phase in laboratory with isooctane as solvent, and on the other hand, dioxin adsorption tests in dynamic gas phase during sampling campaigns on waste incineration site with a very complex matrix.Liquid phase adsorption allowed us to conclude on the effectiveness of materials studied for dioxin adsorption. Adsorption has been after characterized by specific analysis techniques to trace adsorption mechanisms. Adsorption efficiencies were tested in gas phase on a household waste incinerator with the same materials tested in liquid phase in laboratory. Finally, taking into account liquid and gas phase results, two solutions have been proposed for a future commercialized device for on-line dioxin monitoring.

No description available.

A presente tese trata do estudo conformacional e do estudo das interações eletrônicas de alguns 2-(2-haloacetil)-5-substituído: furanos e 1-metilpirrol (Série I), como também dos 2-[2\'-(4\'- substituído-fenilsulfanil)-acetil]-5-metilfuranos, 2-(2\'-substituído-selenil-acetil)-5- metilfuranos (Série II) e 2-[2\'-(4\'- substituídos-fenilsufinil)-acetil]-5-metilfuranos (Série III) contendo substituintes doadores e atraentes de elétrons, além de hidrogênio, na posição 4 do grupo fenila. Foi constatada a ocorrência de isomerismo conformacional por espectroscopia no infravermelho em solventes de constante dielétrica crescente (n-C6-H14, CCl4, CHCl3, CH2Cl2, CH3CN) em todas as séries estudadas. Os resultados obtidos por infravermelho são concordantes com as estruturas obtidas por otimização estrutural no nível de teoria M05-2X/aug-cc-pVTZ para a Série I e M06-2X/aug-cc-pVDZ para as Séries II e III, juntamente com o efeito de solvente simulado pelo método PCM. As interações eletrônicas foram investigadas por meio dos contatos interatômicos e por meio da análise das interações orbitalares (NBO). As estruturas cristalográficas dos compostos 2-[2\'-(4\'- metil-fenilsufinil)- acetil]-5-metilfurano (15) e 2-[2\'-(4\'- cloro-fenilsufinil)-acetil]-5-metilfurano (17) foram obtidas por difração de raio-X. Na Série I quatro conformações estáveis foram reveladas chamadas ac (sin), sp (sin), ac (anti) e sp (anti). Para o derivado do pirrol, há somente confôrmeros com a forma sin em relação ao diedro δ(Xhet-C-C=O), enquanto que nos derivados do furano predomina-se a forma anti. Os dubletos de vCO observados experimentalmente, decorrem do equilíbrio anticlinal (ac) / sinperiplanar (sp) do ângulo diedro α(O=C-C-Z), sendo a forma anticlinal a mais estável e de menor frequência de vCO em todos os compostos. O equilíbrio conformacional sin/anti é regido principalmente pelas interações eletrostáticas, enquanto o anticlinal/sinclinal depende de ambas as interações orbitalares e eletrostáticas. Na Série II para o composto com Z=SeMe foram revelados os confôrmeros ac(anti), o mais estável, e ac(sin), o de maior frequência de vCO, e desestabilizado em decorrência do efeito de campo repulsivo entre os oxigênios do anel aromático e da carbonila. Já para os compostos com Z=SePh, SPhW, ocorrem três conformações estáveis, sc(anti), de menor frequência vCO e maior estabilidade em fase gasosa e condensada, sc(sin) de maior frequência vCO, e ac(anti), que somente é detectada experimentalmente em n-hexano nos compostos com W= MeO, Me e H . Há um aumento gradual da população do confôrmero sc(sin) com o aumento da polaridade do meio. Na Série III, foram revelados três confôrmeros, sc(anti)1 e sc(anti)2 que apresentam interações intramoleculares de empilhamento π-π em fase gasosa, e ac(sin) com populações relativas de no máximo 1% em fase condensada. O aumento da polaridade do meio, de forma geral, estabiliza o confôrmero sc(anti)2 em relação ao confôrmero sc(anti)1. A conformação encontrada em fase sólida para os compostos 15 e 17 são estabilizadas por interações intermoleculares de empilhamento π-π entre os anéis aromáticos fenílicos e furanílicos, bem como por uma série de interações de hidrogênio intermoleculares entre o oxigênio carbonílico e hidrogênios fenílicos / This thesis reports the conformational and electronic interactions study of some 2-(2- haloacetyl)-5-substituted: furans and 1-methylpirrol (Série I), 2-[2\'-(4\'- substitutedphenylsulfanyl)-acetyl]-5-methylfurans plus 2-(2\'-substituted-selenyl-acetyl)-5-methylfurans (Série II) and 2-[2\'-(4\'- substituted-phenylsufinyl)-acetyl]-5-metylfurans (Série III) bearing in the 4-position of the phenyl group electron donating, hydrogen and eletron attracting substituents. It has been found the existence of conformational isomerism through infrared spectroscopy in solventes of increasing dieletric constant (n-C6-H14, CCl4, CHCl3, CH2Cl2, CH3CN) in all studied series. The infrared results are consistent with the conformers obtained by structural optimization on the M05-2X/aug-cc-pVTZ level of theory for Series I and M06- 2X/aug-cc-pVDZ for Series II and III along with the solvent effect calculated by the PCM method. The electronic interactions were investigated from interatomic contacts and by orbital interactions analysis (NBO). Structures for solids of 2-[2\'-(4\'- methyl-phenylsufinyl)-acetyl]- 5-methylfuran and 2-[2\'-(4\'- chloro-phenylsufinyl)-acetyl]-5-methylfuran were obtained through X-ray diffraction analysis. In the series I the computational results predicted the presence of four stable conformers, classified by the orientation of the Xring-C-C=O (syn/anti) and the O=C-C-Z (anticlinal/synperiplanar) moieties as ac(syn), sp(syn), ac (anti) and sp(anti). The anti/syn equilibrium controls the relative stabilities of the conformers to a large extent while the anticlinal/synperiplanar accounts for the observed trend of the IR carbonyl band components. The syn/anti conformational equilibrium is governed mainly by electrostatic interactions, while the anticlinal/synperiplanar depends to different extension both orbital and electrostatic interactions. In serie II for compound with Z=SeMe , have been found ac(anti) as the more stable conformer, and the conformer ac(sin) with the highest vCO frequency which is less stable as a result of the repulsion between the oxygen aromatic ring and the carbonyl oxygen. In the same series for compounds with Z=SePh and SPhW, have been revealed three stable conformations that are sc(anti) the most stable with the lowest vCO frequency, sc(syn) wich has the vCO highest frequency, and ac(anti) which has been detectedexclusively in compounds with Z=MeO, Me and H, in IR n-hexane experimental results. The relative population of the conformer sc(syn) gradually increase when the solvent polarity increases. In series III (Esquema 1) have been revealed three conformers sc (anti)1, ac(syn) and sc(anti)2. The conformers sc(anti)1 and sc (anti)2 have been shown in gas phase intramolecular π-π stacking interaction, and ac (sin) is unstable in solvents. As the polarity medium increases more stable turn the conformer sc(anti)2 than sc(anti)1. The conformer found in solid phase for compounds 15 and 17 is stabilized by intermolecular π-π stacking interaction between the aromatic rings phenyl and furyl, and intermolecular hydrogen bond between the carbonyl oxygen and phenyl hydrogen.

A presente tese trata do estudo conformacional e do estudo das interações eletrônicas de alguns 2-(2-haloacetil)-5-substituído: furanos e 1-metilpirrol (Série I), como também dos 2-[2\'-(4\'- substituído-fenilsulfanil)-acetil]-5-metilfuranos, 2-(2\'-substituído-selenil-acetil)-5- metilfuranos (Série II) e 2-[2\'-(4\'- substituídos-fenilsufinil)-acetil]-5-metilfuranos (Série III) contendo substituintes doadores e atraentes de elétrons, além de hidrogênio, na posição 4 do grupo fenila. Foi constatada a ocorrência de isomerismo conformacional por espectroscopia no infravermelho em solventes de constante dielétrica crescente (n-C6-H14, CCl4, CHCl3, CH2Cl2, CH3CN) em todas as séries estudadas. Os resultados obtidos por infravermelho são concordantes com as estruturas obtidas por otimização estrutural no nível de teoria M05-2X/aug-cc-pVTZ para a Série I e M06-2X/aug-cc-pVDZ para as Séries II e III, juntamente com o efeito de solvente simulado pelo método PCM. As interações eletrônicas foram investigadas por meio dos contatos interatômicos e por meio da análise das interações orbitalares (NBO). As estruturas cristalográficas dos compostos 2-[2\'-(4\'- metil-fenilsufinil)- acetil]-5-metilfurano (15) e 2-[2\'-(4\'- cloro-fenilsufinil)-acetil]-5-metilfurano (17) foram obtidas por difração de raio-X. Na Série I quatro conformações estáveis foram reveladas chamadas ac (sin), sp (sin), ac (anti) e sp (anti). Para o derivado do pirrol, há somente confôrmeros com a forma sin em relação ao diedro δ(Xhet-C-C=O), enquanto que nos derivados do furano predomina-se a forma anti. Os dubletos de vCO observados experimentalmente, decorrem do equilíbrio anticlinal (ac) / sinperiplanar (sp) do ângulo diedro α(O=C-C-Z), sendo a forma anticlinal a mais estável e de menor frequência de vCO em todos os compostos. O equilíbrio conformacional sin/anti é regido principalmente pelas interações eletrostáticas, enquanto o anticlinal/sinclinal depende de ambas as interações orbitalares e eletrostáticas. Na Série II para o composto com Z=SeMe foram revelados os confôrmeros ac(anti), o mais estável, e ac(sin), o de maior frequência de vCO, e desestabilizado em decorrência do efeito de campo repulsivo entre os oxigênios do anel aromático e da carbonila. Já para os compostos com Z=SePh, SPhW, ocorrem três conformações estáveis, sc(anti), de menor frequência vCO e maior estabilidade em fase gasosa e condensada, sc(sin) de maior frequência vCO, e ac(anti), que somente é detectada experimentalmente em n-hexano nos compostos com W= MeO, Me e H . Há um aumento gradual da população do confôrmero sc(sin) com o aumento da polaridade do meio. Na Série III, foram revelados três confôrmeros, sc(anti)1 e sc(anti)2 que apresentam interações intramoleculares de empilhamento π-π em fase gasosa, e ac(sin) com populações relativas de no máximo 1% em fase condensada. O aumento da polaridade do meio, de forma geral, estabiliza o confôrmero sc(anti)2 em relação ao confôrmero sc(anti)1. A conformação encontrada em fase sólida para os compostos 15 e 17 são estabilizadas por interações intermoleculares de empilhamento π-π entre os anéis aromáticos fenílicos e furanílicos, bem como por uma série de interações de hidrogênio intermoleculares entre o oxigênio carbonílico e hidrogênios fenílicos / This thesis reports the conformational and electronic interactions study of some 2-(2- haloacetyl)-5-substituted: furans and 1-methylpirrol (Série I), 2-[2\'-(4\'- substitutedphenylsulfanyl)-acetyl]-5-methylfurans plus 2-(2\'-substituted-selenyl-acetyl)-5-methylfurans (Série II) and 2-[2\'-(4\'- substituted-phenylsufinyl)-acetyl]-5-metylfurans (Série III) bearing in the 4-position of the phenyl group electron donating, hydrogen and eletron attracting substituents. It has been found the existence of conformational isomerism through infrared spectroscopy in solventes of increasing dieletric constant (n-C6-H14, CCl4, CHCl3, CH2Cl2, CH3CN) in all studied series. The infrared results are consistent with the conformers obtained by structural optimization on the M05-2X/aug-cc-pVTZ level of theory for Series I and M06- 2X/aug-cc-pVDZ for Series II and III along with the solvent effect calculated by the PCM method. The electronic interactions were investigated from interatomic contacts and by orbital interactions analysis (NBO). Structures for solids of 2-[2\'-(4\'- methyl-phenylsufinyl)-acetyl]- 5-methylfuran and 2-[2\'-(4\'- chloro-phenylsufinyl)-acetyl]-5-methylfuran were obtained through X-ray diffraction analysis. In the series I the computational results predicted the presence of four stable conformers, classified by the orientation of the Xring-C-C=O (syn/anti) and the O=C-C-Z (anticlinal/synperiplanar) moieties as ac(syn), sp(syn), ac (anti) and sp(anti). The anti/syn equilibrium controls the relative stabilities of the conformers to a large extent while the anticlinal/synperiplanar accounts for the observed trend of the IR carbonyl band components. The syn/anti conformational equilibrium is governed mainly by electrostatic interactions, while the anticlinal/synperiplanar depends to different extension both orbital and electrostatic interactions. In serie II for compound with Z=SeMe , have been found ac(anti) as the more stable conformer, and the conformer ac(sin) with the highest vCO frequency which is less stable as a result of the repulsion between the oxygen aromatic ring and the carbonyl oxygen. In the same series for compounds with Z=SePh and SPhW, have been revealed three stable conformations that are sc(anti) the most stable with the lowest vCO frequency, sc(syn) wich has the vCO highest frequency, and ac(anti) which has been detectedexclusively in compounds with Z=MeO, Me and H, in IR n-hexane experimental results. The relative population of the conformer sc(syn) gradually increase when the solvent polarity increases. In series III (Esquema 1) have been revealed three conformers sc (anti)1, ac(syn) and sc(anti)2. The conformers sc(anti)1 and sc (anti)2 have been shown in gas phase intramolecular π-π stacking interaction, and ac (sin) is unstable in solvents. As the polarity medium increases more stable turn the conformer sc(anti)2 than sc(anti)1. The conformer found in solid phase for compounds 15 and 17 is stabilized by intermolecular π-π stacking interaction between the aromatic rings phenyl and furyl, and intermolecular hydrogen bond between the carbonyl oxygen and phenyl hydrogen.

The homoaldol reaction is one of the most powerful methods for the construction of C–C bonds as well as 1,4-oxygenated compounds yet this reaction remains in challenging tasks due to the instability of homoenolates which spontaneously cyclize to the cyclopropanolate. A regioselective catalytic homoaldol equivalent reaction of 3-bromo vinyl acetate with aldehydes under Cr(III)-Mn(0) redox condition was developed. This homoaldol equivalent reaction allows access to the 1,4-oxygenated compounds that are not possible by a conventional aldol process. Mild hydrolysis of the vinyl acetate and reduction of the homoaldol adducts generated diols and lactols in high yield (99%). Further manipulation including stereoselective epoxidation and cyclopropanation was achieved in an efficient manner. Furans, found in many natural products and utilized in drug discovery, have been well studied but current synthetic methods toward furans have some limitations in functional group tolerance, substrate scope, and low product yield in many cases. A highly efficient and catalytic cycloisomerization reaction that transforms acetylenic α,β-epoxides to 2,3,5-tri-substituted furans under InCl3 catalysis was developed. This reaction sequence allows access to rapid construction of highly valuable, tri-substituted furan derivatives. Cross-coupling reactions utilizing transition metals and Lewis acids are important synthetic tools for the formation of C–C and C–N bonds and a number of cross-coupling reactions between α-bromo carbonyl compounds and metal reagents such as aryl metals, alkenyl metals, and alkyl metals have been reported. Transition metal-catalyzed cross-coupling reaction for the construction of α-alkynyl carbonyl compounds has reported in a limited case. The first approach to secondary α-alkynyl carbonyl compounds from secondary α-bromo esters and amides with tributyl(phenylethynyl)stannane under palladium-catalyzed cross-coupling reaction conditions was developed. This synthetic method allows access to secondary α-alkynyl carbonyl compounds which are valuable precursors in pharmaceuticals and agricultural applications.