Dissertations / Theses on the topic 'Dithane'

Plant diseases caused by fungi are the number one cause of crop loss worldwide. The application of a fungicide which is a toxic substance applied either to prevent the growth of, or to kill fungi is one of the methods by which plant diseases are controlled. Ethylenebisdithiocarbamate fungicides are a group of surface acting fungicides which control a broad spectrum of fungi and their associated plant diseases. Mancozeb, also commonly known as Dithane, falls under the polymeric Dithiocarbamate fungicides which have several sites of toxicity to the fungal cell. The use of Mancozeb as a fungicide is increasing worldwide due to the advantages of low acute toxicity, low production and short environmental persistence. However, it has one major disadvantage, namely its lack of oxidative stability under ambient conditions. One of the objectives of this study was to characterize the Dithane samples supplied by Dow AgroSciences in terms of their active ingredient, metal and stabilizer content, and to study the thermal decomposition behaviour of Dithane. An attempt was made to correlate the active ingredient analyses with the TGA and DSC results to establish whether the thermal stability and active ingredient content of Dithane could be simultaneously determined by thermal analysis. This approach offered the attractive advantage of shorter analysis times thus allowing the elimination of the more tedious analytical methods employed by Dow AgroSciences. Furthermore, Fourier Transform infra-red characterization of Dithane samples and metal complexes containing HMT, Mn and/or Zn was carried out in order to identify the presence of functional groups and to gain some insight into the nature of the bonding of HMT, sulfate and water. A study of the nature of the bands in the FTIR spectra of these complexes was able to highlight the nature of the bonding but could not give confirmation of the structures of these complexes. In addition to this, the amount of HMT present in the said complexes was determined by the FTIR using the standard addition method. A final objective of the study was to investigate the reconstitution of Dithane by investigating the influence of the addition order of the various constituents on the stability of the final product. The addition order was found to have a definite influence on the thermal stability of the final product as well as on the percentage of fixed HMT in the product, and the kinetics of the Mn/Zn exchange.

This doctoral thesis is divided into three sections: Part A, Part B and Part C. Part A is subdivided further into three chapters. In the first of these, an overview of the Julia olefination reaction process as well as its variants is provided, followed by a short description of the application of dithiane methodology in natural product synthesis. The second chapter describes the development of a new methodology based on Julia olefination of substrates derived from dithiane and dithiolane sulfones. Summary and conclusions then follow in chapter three. Part B of this thesis is also subdivided into three sections. The first chapter focuses on the discovery of the callipeltoside natural product family and in this context, structure elucidation and previous total syntheses of callipeltoside A are described. The second chapter outlines the successful synthesis of gram quantities of the crucial aldehyde fragment for the Ley group callipeltoside A synthesis using the double addition of dithiols to ynones developed within the group. Then a preliminary study of the coupling of this key intermediate with a diverse range of vinyl iodide fragments en route to callipeltoside A is described. Full summary, conclusions and details of future work towards completion of the synthesis of calipeltoside A are provided in the third chapter. Finally, a detailed description of experimental procedures and full analytical characterisation data are provided in Part C of this thesis.

PARENTE, Marcelo Valente. Estudo eletroquímico da adsorção de moléculas organosulfuradas sobre superfície de ouro. 2006. 96 f. Tese (Doutorado em Química Inorgânica) – Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2006.
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Modified gold surface with organosulfur species, 1,4-dithiane (1,4-dt) and 4- mercaptopyridine (pyS), was studied in this work. The study was carried out using the following electrochemical techniques: linear polarization with rotate disk electrode, cyclic voltammetry, differential pulse voltammetry, electrohydrodynamic impedance and electrochemical impedance spectroscopy. Other techniques also gave support, such as, atomic force microscopy (AFM), Scanning tunneling microscopy (STM), RAMAN spectroscopy and quartz crystal microbalance (QCM). For the modified gold surface with the 1,4-dt, it was observed the decrease of the redox-active [Fe(CN)6]3- species with the increase of the immersion time of the gold electrode in the modifier solution. These results suggest that the fractional coverage increases with the modification time. The electrohydrodynamic impedance results together with the MFA and MST results suggest that this surface is partially blocked presenting defects on the formed film. The RAMAN spectra suggest that those defects can be resulting of the adsorption of the different configuration of the modifier molecules (1,4-dt) on the surface ("trans" and "gauche"). The electrochemical results about the modified gold surfaces with the molecule pyS indicate an increase of the electron transfer process with the increase of the immersion time, which suggests the loss of the covering power on the modified gold surface with this species. The AFM results agree the previous results demonstrating that this surface presents larger amount of defects for longer modification times. The frequency curves variation (ΔF) versus the immersion time indicate a mass increase on the modified gold surface with the species 1,4-dt and a process desorption for the species pyS confirming the results obtained previously.
Superfície de ouro modificada com as espécies 1,4-ditiano (1,4-dt) e 4- mercaptopiridina (pyS), foram estudadas neste trabalho. Para a realização desse estudo foram utilizadas as seguintes técnicas eletroquímicas: polarização linear com eletrodo de disco rotatório, voltametria cíclica, voltametria de pulso diferencial, impedância eletro-hidrodinâmica e espectroscopia de impedância eletroquímica. Outras técnicas também deram suporte, tais como, microscopia de força atômica (MFA), microscopia de superfície por tunelamento (MST), espectroscopia RAMAN e microbalança de quartzo (MBQ). Para as superfícies modificadas com a molécula 1,4-dt, foi observado a diminuição do processo redox [Fe(CN)6]3-/4- com o aumento do tempo de imersão do eletrodo de ouro na solução modificadora. Estes resultados sugerem que taxa de recobrimento da superfície de ouro, com esta espécie, aumenta com o tempo de modificação. Os resultados de impedância eletro-hidrodinâmica juntamente com as micrografias MFA e MST revelam que esta superfície está parcialmente bloqueada apresentando defeitos sobre o filme formado. Os resultados de espectroscopia RAMAN sugerem que esses defeitos podem ser resultantes da adsorção das conformações diferenciadas na forma de “cadeira” e “barco” da molécula 1,4 dt. Por outro lado, os resultados eletroquímicos com as superfícies modificadas com a espécie pyS indicam um aumento do processo de transferência de carga com o aumento do tempo de imersão do eletrodo de ouro na solução modificadora. Este resultado sugere a perda do poder de cobertura para a superfície de ouro modificada com esta espécie. Os resultados de MFA reforçam os resultados anteriores para esta espécie demonstrando que esta superfície apresenta maiores quantidade de defeitos para tempos mais longos de modificação. As curvas de variação de freqüência (ΔF) versus tempo de modificação indicam um aumento de massa na superfície de ouro modificada com a espécie 1,4-dt, enquanto que para a espécie pyS observa-se um processo de desorção, confirmando qualitativamente os resultados obtidos anteriores para estas duas moléculas.

Les amphidinols sont une nouvelle classe de molécules naturelles de type polycétide dont l'amphidinol-3 est la seule molécule possédant sa structure entièrement établie. L'amphidinol-3 exhibe les meilleures activités biologiques de cette famille, principalement antifongique ethémolytique. La synthèse du fragment C17-C30 a été le premier objectif de ces travaux de thèse. Cette synthèse est basée sur l'utilisation du para-tolylsulfoxyde comme auxiliaire de chiralité et d'un bromoallylsilane comme corps central. Tous les centres asymétriques sont contrôlés avec de très hauts rapports diastéréomériques à l'exception de la configuration du méthyle en C23. La non-maîtrise de ce centre, ainsi que des difficultés probables de couplage nous ont obligés à repenser notre stratégie. Suite au changement rétrosynthétique, la synthèse du fragment C13-C29 a été réalisée. L'étape clef de cette voie synthétique est alors le couplage entre l'anion lithié d'un dérivé de 1,3-dithiane avec un aldéhyde α-branché. Après de nombreux ajustements de groupements protecteurs, le fragment C13-C29 est obtenu avec tous ses centres asymétriques maîtrisés.

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CAPES; CNPq
Os agrotóxicos são largamente utilizados no mundo para proteger as plantações contra pragas e doenças, e na saúde pública no controle de vetores que causam doenças ao homem. Contudo, a exposição a esses produtos pode representar graves riscos à saúde humana e ao meio ambiente. Relatos da literatura sobre ação genotóxica das formulações comerciais isoladas de agrotóxicos é bastante escaça, uma vez que a maioria das pesquisas se preocupa em estudar o efeito das misturas desses compostos. Desta forma, o presente trabalho realizou um biomonitoramento in vivo, utilizando camundongos Mus musculus, para avaliar a ação genotóxica aguda, através da ingestão isolada dos agrotóxicos Ciromazina (Trigard 700 WP) e Maconzeb (Dithame NT) em baixas doses. Foram realizados os testes do micronúcleo e do ensaio cometa, para avaliar respectivamente a mutagenicidade e a genotoxicidade desses pesticidas. Sendo utilizados 80 camundongos, divididos em oito grupos contendo 10 animais (cinco machos e cinco fêmeas). As administrações foram feitas por gavagem e cada animal recebeu 1 mL da solução, de acordo com o grupo a que pertencia: o grupo controle negativo recebeu apenas o veículo de diluição (água destilada); para a Ciromazina foram usados três grupos experimentais: C1 com a concentração de 2,5.10−4 mg/Kg, o C2 com a concentração de 5.10−4 mg/Kg, e C3 com a concentração de 5.10-3 mg/Kg; para o Mancozeb foram usados também três grupos experimentais: C1 com a concentração de 3,76.10−4 mg/Kg, C2 com a concentração de 7,52.10−4 mg/Kg, e C3 com a concentração de 7,52.10-3 mg/Kg; para o grupo controle positivo foi administrado via injeção intraperitonial 20 mg/kg p.c. de ciclofosfamida. Na análise estatística, foram realizados dois testes: uma ANOVA multifatorial (Análise de variância), para comparar a ação genotóxica entre os grupos experimentais; e o teste de Mann-Whitney para verificar a influência do sexo no aparecimento do dano genético dentro de um mesmo grupo tratado. O agrotóxico Ciromazina demonstrou ser mutagênico e altamente genotóxico na concentração do grupo C2, além de apresentar uma diferença significativa entre os sexos no grupo C1. Já o pesticida Mancozeb mostrou ser genotóxico na concentração do grupo C2, e foi constatado também que houve diferença significativa entre os sexos dos individuos do grupo C3. Através desta pesquisar evidenciamos que mesmo em baixas concentrações estes pesticidas oferecem grandes riscos à saúde humana e ao meio ambiente.

11-(1,3-Dithian-2-yl)-13-tetradecanolide (71) was synthesized in a ten step sequence in approximately 3% overall yield. Alkylation of this compound with methyl iodide yielded a 6:1 mixture of diastereomers 72 and 73, the major isomer being 72. The stereochemistry at C-2 of these compounds was determined by their conversion to 74 and 75. respectively, whose stereochemistry was known. Results of molecular mechanics calculations suggest that the alkylation reaction proceeds through either of the low energy [3335] or [3344] conformations, both of which give rise to the observed product ratio.[See Thesis for Diagram]
Science, Faculty of
Chemistry, Department of
Graduate

A review of organic, π-electron donor molecules is given. The focus is on non- tetrathiafulvalene based systems. Polycyclic arenes, thioalkyl substituted arenes, chalcogenated fulvalenes, peri-dichalcogen bridged polycyclic arenes and heteroarenes are covered. Various π-electron donor molecules based on acenaphtho[ 1,2-b][ 1,4]-dithin have been synthesised via various methodologies. The redox properties of these molecules, as studied by cyclic voltammetry, provide evidence that these species are efficient π-electron donors. A selection of these compounds have also been studied by Electron Spin Resonance. Two ring expansion methodologies have been utilised in the synthesis of acenaphtho[l,2-b][l,4]-dithin based systems from 1,2-dithiols. Complexation of 7,12- dithia-benzo[k]fluoranthene, thus synthesised, with 2,5-dibromo-7,7,8,8-tetracyano-p- quinodimethane and iodine (I(_4) counter ion) yielded highly crystalline but poorly conducting salts.1,2-Dibromoacenaphthylene and benzo-l,2-dithiolate species have been reacted to form new 7,12-dithia-benzo[k]fluoranthene derivatives, two of which have been studied by X-ray diffraction. The versatile oligo(l,3-dithiole-2,4,5-trithione) compound has been used to generate various compounds containing the 1,4-dithiin ring including 8,9- di(methylsulfanyl)acenaphthyleno[l,2-b][l,4]dithine, which forms complexes with 7, 7,8,8-tetracyano-p-quinodimethane, 2,5-dibromo-7,7,8,8-tetracyano-p-quinodimethane and iodine (I(_7) counter ion) all three of which have been studied by X-ray diffraction. A novel 1,2,4-trithiolane has also been synthesised and characterised by X-ray diffraction.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
SuperfÃcie de ouro modificada com as espÃcies 1,4-ditiano (1,4-dt) e 4- mercaptopiridina (pyS), foram estudadas neste trabalho. Para a realizaÃÃo desse estudo foram utilizadas as seguintes tÃcnicas eletroquÃmicas: polarizaÃÃo linear com eletrodo de disco rotatÃrio, voltametria cÃclica, voltametria de pulso diferencial, impedÃncia eletro-hidrodinÃmica e espectroscopia de impedÃncia eletroquÃmica. Outras tÃcnicas tambÃm deram suporte, tais como, microscopia de forÃa atÃmica (MFA), microscopia de superfÃcie por tunelamento (MST), espectroscopia RAMAN e microbalanÃa de quartzo (MBQ). Para as superfÃcies modificadas com a molÃcula 1,4-dt, foi observado a diminuiÃÃo do processo redox [Fe(CN)6]3-/4- com o aumento do tempo de imersÃo do eletrodo de ouro na soluÃÃo modificadora. Estes resultados sugerem que taxa de recobrimento da superfÃcie de ouro, com esta espÃcie, aumenta com o tempo de modificaÃÃo. Os resultados de impedÃncia eletro-hidrodinÃmica juntamente com as micrografias MFA e MST revelam que esta superfÃcie està parcialmente bloqueada apresentando defeitos sobre o filme formado. Os resultados de espectroscopia RAMAN sugerem que esses defeitos podem ser resultantes da adsorÃÃo das conformaÃÃes diferenciadas na forma de âcadeiraâ e âbarcoâ da molÃcula 1,4 dt. Por outro lado, os resultados eletroquÃmicos com as superfÃcies modificadas com a espÃcie pyS indicam um aumento do processo de transferÃncia de carga com o aumento do tempo de imersÃo do eletrodo de ouro na soluÃÃo modificadora. Este resultado sugere a perda do poder de cobertura para a superfÃcie de ouro modificada com esta espÃcie. Os resultados de MFA reforÃam os resultados anteriores para esta espÃcie demonstrando que esta superfÃcie apresenta maiores quantidade de defeitos para tempos mais longos de modificaÃÃo. As curvas de variaÃÃo de freqÃÃncia (ΔF) versus tempo de modificaÃÃo indicam um aumento de massa na superfÃcie de ouro modificada com a espÃcie 1,4-dt, enquanto que para a espÃcie pyS observa-se um processo de desorÃÃo, confirmando qualitativamente os resultados obtidos anteriores para estas duas molÃculas.
Modified gold surface with organosulfur species, 1,4-dithiane (1,4-dt) and 4- mercaptopyridine (pyS), was studied in this work. The study was carried out using the following electrochemical techniques: linear polarization with rotate disk electrode, cyclic voltammetry, differential pulse voltammetry, electrohydrodynamic impedance and electrochemical impedance spectroscopy. Other techniques also gave support, such as, atomic force microscopy (AFM), Scanning tunneling microscopy (STM), RAMAN spectroscopy and quartz crystal microbalance (QCM). For the modified gold surface with the 1,4-dt, it was observed the decrease of the redox-active [Fe(CN)6]3- species with the increase of the immersion time of the gold electrode in the modifier solution. These results suggest that the fractional coverage increases with the modification time. The electrohydrodynamic impedance results together with the MFA and MST results suggest that this surface is partially blocked presenting defects on the formed film. The RAMAN spectra suggest that those defects can be resulting of the adsorption of the different configuration of the modifier molecules (1,4-dt) on the surface ("trans" and "gauche"). The electrochemical results about the modified gold surfaces with the molecule pyS indicate an increase of the electron transfer process with the increase of the immersion time, which suggests the loss of the covering power on the modified gold surface with this species. The AFM results agree the previous results demonstrating that this surface presents larger amount of defects for longer modification times. The frequency curves variation (ΔF) versus the immersion time indicate a mass increase on the modified gold surface with the species 1,4-dt and a process desorption for the species pyS confirming the results obtained previously.

Cette thèse porte sur l'étude de la synthèse des éléments C et B du Sesbanimide A. L'approche de synthèse que nous avons adoptée, consiste à prendre un sucre en C-4, représentant les carbones 4, 7, 8 et 9 du sesbanimide A à effectuer une condensation entre le carbone 9 et l'anion α des atomes de soufre du dithiannyl-3 méthylène-2 butanol-1 représentant les cycle C. Le produit de la condensation présente les carbones 4 et 7 à 13puis 15 et 16 du Sesbanimide A.

Les acylsilanes sont les composés «acyl-métal» présentant la chimie la plus diversifiée. Cette thèse porte d'une part sur de nouvelles synthèses (méthodes et produits) d'acylsilanes, d'autre part sur l'étude de leur réactivité. Plus particulièrement, des allyl- et vinyl(acyl)silanes et des bis(acylsilanes) à silicium internes étaient ciblés. Une synthèse basée sur l'hydrolyse d'éthers d'énol ou d'ènethiol C-silylés s'est révélée peu performante pour des bis(acylsilanes), mais apporte une contribution originale à la panoplie des méthodes de synthèse d'acylsilanes. Deux méthodes ont été étudiées pour la synthèse d'allyl- et vinyl(acyl)silanes. Une séquence silylation/déthiocétalisation du 2-phényl-[1,3]-dithiane a permis de préparer les allyl- et vinyl(benzoyl)silanes, et la méthode à été étendue à d'autres allyl(acyl)silanes. Une séquence silylation/alkylation du 1-phénoxyméthyl-1H-benzotriazole a conduit efficacement aux allyl- et vinyl(acyl)silanes à longue chaîne alkyle. Les allyl- et vinyl(acyl)silanes se sont révélés peu réactifs en métathèse. Cependant la métathèse cyclisante appliquée aux dérivés bis(insaturés) du benzotriazole a donné des intermédiaires cycliques avec de très bons rendements. La métathèse croisée appliquée à un allylsilane dérivé du benzotriazole a permis d'obtenir, après hydrolyse, le bis(acylsilane) correspondant. Les allyl(diméthyl)(acyl)silanes présentent une réactivité photochimique inédite comparée à celle des acyl(trialkyl)silanes. Les allyl(acyl)silanes donnent, par réaction de Paternò-Büchi intramoléculaire totalement régiosélective, des 1-alkyl-2,2-diméthyl-6-oxa-2- sila-bicyclo[2. 2. 0]hexanes, un nouveau type de structure bicyclique
Acylsilanes are «acyl-metal» compounds having the most varied chemistry. This PhD concerns, on the one hand, new synthesis (methods and products) of acylsilanes, on the other hand the study of their reactivity. A method of synthesis based on the hydrolysis of C-silyl enol or enethiol ethers proved to be inappropriate for the preparation of bis(acylsilanes), but provided an original contribution to the array of the acylsilanes synthetic methods. The synthesis of allyl- and vinyl(acyl)silanes and allyl- and vinyl(aroyl)silanes was performed from two types of precusors. Allyl- and vinyl(benzoyl)silanes were prepared by a sequence of silylation/dithioketalisation of 2-phenyl-[1,3]-dithiane and the methodology was extended to aliphatic allyl(acyl)silanes. A sequence silylation/alkylation applied to 1-phenoxyméthyl-1Hbenzotriazole led to allyl- and vinyl(acyl)silanes bearing a long alkyl chain in satisfactory yields. Allyl- and vinyl(acyl)silanes proved to have a poor reactivity in metathesis whatever the Grubbs catalyst used. However ring closing metathesis applied to bis(unsaturated) benzotriazole derivatives led to cyclic intermediates in very good yields. Cross-metathesis applied to an allysilane derived from benzotriazole led, after deprotection, to the expected bis(acylsilane). Allyl(dimethyl)(acyl)silanes exhibited an unexpected reactivity compared with the usual reactivity of acyl(trialkyl)silanes. UV irradiation of allyl(acyl)silanes gave 1-alkyl-2,2-diméthyl-6-oxa-2-sila-bicyclo[2. 2. 0]hexanes, a new type of bicyclic structure, by a totally regioselective intramolecular Paternò-Büchi reaction

Plusieurs molécules nouvelles ont été obtenues à partir du Gossypol, extrait des graines de cotonnier. Dans la première partie, de nouvelles bases de Schiff du gossypol et de la gossypolone ont été synthétisées, les énantiomères du gossypol et leurs bases de Schiff sont optiquement stables, tandis que, les énantiomères de la gossypolone ne sont pas stables à température ambiante, mais il est possible de les observer vers 0°C. La cytotoxicité de ces bases de Schiff a été évaluée principalement sur des cellules KB, la méthylimine et l'éthylimine de la gossypolone sont les plus toxiques (IC50= 0.8 et 1.2 µM). La toxicité du gossypol et de la gossypolone augmente quand les tests sont effectués en absence de sérum et elle diminue en présence de catalase ou de mannitol dans le milieu de culture. L'énantiomère (-)-gossypol est plus toxique que le (+)-gossypol, ceci est aussi valable pour les bases de Schiff des énantiomères du gossypol. Dans la deuxième partie, une nouvelle classe de dérivés du gossypol et de la gossypolone, les dithianes et les dithiolanes, a été développée. Les dithianes/dithiolanes du gossypol et de la gossypolone ont été synthétisés par action de dithiols en présence d'éthérate de trifluoroborate. La même réaction effectuée avec les monothiols, conduit à des mélanges complexes. L'action du propanedithiol ou de l'ethanedithiol sur le tetraméthyle ou l'hexaméthyle éthers du gossypol ne conduit pas aux dithianes ou dithiolanes attendus mais à de nouveaux dérivés cycliques. La toxicité de ces nouveaux thio-dérivés sur les cellules KB est assez modeste, mais sous l'action de NO ou d'un sel de nitrosonium, ces dérivés se transforment en dérivés plus toxiques dans le cas du gossypol ou régénèrent la molécule de départ dans le cas de la gossypolone. Nous formulons l'hypothèse que dithianes et dithiolanes du gossypol et de la gossypolone pourraient être des modèles de prodrogues ciblées sur les cellules exprimant de fortes concentrations d'oxyde nitrique.

Etude de l'emploi d'un coordinat assembleur qui puisse par coordination avec le centre metallique utilise (metaux de transition du groupe viii) aboutir a un agencement a une dimension des motifs moleculaires par empilement d'entites monomeres ou par formation de chaines. Par utilisation du coordinat squarate sous ses formes oxygenees et soufrees, obtention d'un certain nombre de complexes de pt, pd, ni et cu repondant aux criteres fixes. Etude des structures de ces composes, de leurs proprietes physiques et de la relation structure-propriete. La nature du coordinat comme le caractere specifique de l'arrangement structural ont ete discutes pour une approche de la comprehension de la nature de ces proprietes physiques

Nos travaux s'inscrivent dans le domaine de la chimie des cétohexoses et en particulier de deux d'entre eux : le D-fructose et le D-psicose. En vue de l'évaluation des potentialités biologiques de ces oses, nous avons d'abord étudié les voies'd'accès à des nucléosides dérivés du D-fructofuranose puis la synthèse de composés aminés issus de cet ose et du D-psicofuranose. Cette approche nous a amené à mettre au point la préparation d'un dérivé du D-psicofuranose comportant une différenciation au niveau de ses deux hydroxyméthyles. Ce composé devrait permettre de résoudre certains problèmes synthétiques inhérents à la chimie des cétohexoses et qui n'avaient pas trouvé jusqu'ici de solution satisfaisante.

M.A.
Riddles, together with other genres such as idioms, proverbs and legends, form an important and integral component of what is commonly referred to as oral literature. Riddling is a traditional game, mainly engaged in by the youth, as a positive and constructive way of whiling away time. This game is not only confined to tribes and communities in Southern Africa, but is also played throughout the African continent and also in many parts of the world ...

Creating new carbon-carbon bonds is one of the most important and challenging reactions in organic synthesis. Metal-catalyzed cross-coupling reactions have emerged as one of the preferred methods of producing new carbon-carbon bonds, and this work led to the 2010 Nobel Prize in Chemistry. This thesis was aimed at expanding the current research in the area of metal-catalyzed cross-coupling reactions to include new applications with dithiolane and dithiane protecting groups. 1,3-Dithiolane and 1,3-dithiane derivatives are particularly interesting molecules in that they can be deprotonated by a strong base to form anions, which can then be used for carbon-carbon bond synthesis. This thesis describes the investigation into the use of dithiolanes and dithianes in metal-catalyzed cross-coupling reactions, as well as some of the challenges faced in performing this sulfur-based chemistry.

Philosophiae Doctor - PhD
This thesis is based on the study of electropolymerization and electrochromism of poly(4,7- dithien-2-yl-2,1,3-benzothiadiazole) (P(DTBT) and its copolymer with 3-methoxythiophene (MOT) in imidazolium ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimbf4) hydrophilic, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimpf6) and 1- butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (bmimtnf2) hydrophobic ILs. Traditional organic solvents acetonitrile and dichloromethane in the presence of 0.1 M tetrabutylammonium perchlorate (n-Bu4NClO4) as a supportive electrolyte was also used as a medium for comparison. Besides, a more hydrophobic ionic liquid, 1-octyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide (octmimtnf2) was also used for the electrodeposition of poly(3-methoxythiophene) (PMOT). The techniques employed are cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), uv-visible spectroelectrochemistry and scanning electron microscopy (SEM). 4,7-Dithien-2-yl-2,1,3-benzothiadiazole (DTBT) a type of donor –acceptor monomer and 3- methoxythiophene (MOT) has been electropolymerized using ionic liquids as growth and supportive electrolytes.

碩士
國立臺灣大學
化學學系
81
The NiCl2(PPh3)2 catalyzed cross-coupling reactions of Grignard eagents with dithianes having β-OR or β-SR group at C2 positionead to the regioselective formation of the double bond via β-ORr β-SR elimination process. The rate of β- OR or β-SRlimination appears to be faster than the rates of cyclopropyling opening rearrangement and β-hydride elimination. Variousvidences suggest that the reaction may proceed via orangonickelntermediate from which the β-OR or β-SR group is eliminated.o exchange between nickel and magnesium may occur.

This study focused on the psychosocial effects and coping mechanisms of black widows in the Mafikeng area following the death of their spouses. A descriptive research design was used in collecting data. A sample of forty-eight black widows aged between twenty-five and seventy years was randomly selected for the purpose of this study. A questionnaire was administered to the sample. This questionnaire contained both open-ended and close-ended questions. Beck's Depression Inventory was also used in the collection of data to assess the level of depression if any. A descriptive statistical analysis of data was used to analyse the collected data. The findings indicated that most black widows experience psychological problems such as loneliness and depression due to withdrawal. There was also an indication that most black widows experienced social problems like being discriminated against and rejection by friends, relatives as well as neighbours due to the stigma associated with widowhood. However, there is an indication that some black widows do experience a positive perception from their employers and have a positive relationship with their in-laws. This study also confirmed that some black widows use inappropriate coping mechanisms such as withdrawal from the societal activities in fear of humiliation in dealing with their widowhood. Some resort to religion as another way of coping with their loss. The majority of older widows considered remarriage as a poor option while younger widows considered remarriage as viable. The grip on widows by traditional rituals is also diminishing especially among young, successful and educated widows. Having undertaken this study the implication is that black widows are mainly stigmatized in the society in which they live. They are even humiliated through restrictions that are put before them. For instance, performance of rituals and customs. Some of those who are employed experience a negative perception from both their employers and their colleagues because of the stigma. However. there still some black widows who still enjoy the moral support of their in-laws, employers and also that of their colleagues.
M.A. (Clinical Psychology) North-West University, Mafikeng Campus, 2005

Abstracts in Afrikaans, English and Southern Sotho
Geweld en skoolgeweld veroorsaak ernstige maatskaplike ontwrigting in Suid-Afrika. Die metodes waarmee skoolgeweld tans hanteer word, is oneffektief en meestal op mag en dissipline gegrond. Die doel van hierdie navorsing is om alternatiewe benaderings vir die hantering van skoolgeweld te ondersoek en om ʼn implementeringsraamwerk vir ʼn heelskoolbenadering teen skoolgeweld te ontwikkel. Ten einde hierdie doel te bereik, fokus die navorsing, wat binne ʼn aangepaste ekologiese model (AEM) onderneem is, op ʼn konseptuele analise van die aard en inhoud van die konsepte “geweld” en “skoolgeweld”, omdat beide dikwels met konsepte soos “mag” en “dissipline” verwar word. Beide begrippe is multidimensioneel en kom binne al die sfere van die AEM voor. Dit sluit geweld weens verskeie oorsake, soos psigo-biologiese faktore, strukturele geweld en reaksiegeweld in. Skoolgeweld kom eweneens weens verskeie oorsake en in verskillende vorms binne die sfere van die AEM voor. Voorbeelde sluit lyfstraf, boeliegedrag, bendes en strukturele skoolgeweld soos rassisme, die kwaliteit van onderwys en oorvol klasse, in. Die navorsing toon aan dat die wyse waarop skoolgeweld tans in Suid-Afrika hanteer word, onsuksesvol is. Dit word hoofsaaklik by wyse van mag, dissipline en ʼn strafbenadering hanteer, wat meebring dat die verhoudings wat weens die geweld beskadig word of skipbreuk ly, versoening tussen dader en slagoffer verhoed en dat die slagoffer se behoeftes nie in ag geneem word nie. Die wyse waarop skoolgeweld hanteer word, bied ook nie ʼn wyse waarop strukturele skoolgeweld bestuur kan word nie. Een van die alternatiewe wyses waarop skoolgeweld hanteer kan word, is herstellende onderwys. Dit is ʼn betreklik nuwe benadering tot onderwys, wat op herstellende geregtigheid gegrond is, maar ook proaktiewe aktiwiteite insluit. Omdat herstellende onderwys op beginsels soos verhoudings, dialoogvoering, waardegedrewenheid, herstel en versoening gegrond is, kan dit gebruik word om skoolgeweld te beheer. Herstellende onderwys maak van verskillende proaktiewe en reaktiewe metodes gebruik, soos slagoffer-oortrederbemiddeling en groepsgesprekke. Dit fokus op ʼn skoolgemeenskap wat waardegedrewe is, eerder as op oortredings. Herstellende onderwys word egter deur ʼn aantal knelpunte gekniehalter. Die navorsing toon aan dat hierdie knelpunte deur die Freire se benadering tot onderwys ondervang kan word. Freire se benadering tot onderrig word aan die hand van ʼn aantal kernelemente, wat in vyf groepe verdeel is (naamlik sy siening oor mag en bemagtiging, etiesgodsdienstige elemente, bewustheid en aksie, dialoogvoering, onderwyspraktyk en onderwys en die samelewing) hanteer. Die navorsing toon aan dat hierdie elemente gebruik kan word om die leemtes in herstellende onderwys te vul en dat die twee benaderings en ʼn aantal ander benaderings wat daarby aansluit, soos onderwys vir maatskaplike geregtigheid, kritiese pedagogiek en die leerstellings van Mohlomi, tot ʼn geïntegreerde onderwysbenadering – geïntegreerde helende onderwys – saamgevoeg kan word. In die voorlaaste gedeelte van die navorsing word die beginsels van geïntegreerde helende onderwys gebruik om ʼn praktykgerigte implementeringsraamwerk te ontwikkel. Die raamwerk word in twee dele hanteer: eerstens die implementeringsterreine, naamlik die geleerde en geleefde leerplanne, en tweedens die implementeringsproses wat deur middel van deelnemende aksienavorsing uitvoer kan word. Die navorsing sluit af met ʼn opsomming van die navorsing, ʼn uitwysing van die beperkings van die studie en aanbevelings vir verdere ondersoek.
Violence and school violence play havoc with South African society. Current methods to curb school violence depend on power, discipline and a penal approach, and prove to be ineffective. The purpose of this research was to investigate alternative approaches to manage school violence and develop an implementation framework for a whole-school approach to it. This research was conducted according to an integrated ecological model. The concepts “violence” and “school violence” were analysed as they are often confused with the concepts “power” and “discipline”. The former pair of concepts are multidimensional and present in all spheres of the integrated ecological model. They include individual violence, group violence and structural violence. School violence manifests in different forms, including bullies and gangs. This research differentiates between controllable school violence – which is within the school community’s sphere of influence – and manageable school violence – which originates outside the school community. The research indicates that the ways in which school violence is currently addressed do not consider damaged relationships because of violence, reconciliation between the perpetrator and the victim, and the needs of the victim. In addition, they do not contribute to the management of structural school violence. Restorative education is a recent approach based on restorative justice and includes proactive activities. Because it is value-driven and grounded on relationships, dialogue, restoration and reconciliation, it can be of great use in the fight against school violence. Restorative education includes both proactive and reactive methods such as victim-offender mediation and group discussions. It focuses on a value-driven school community rather than infringements. However, restorative education has certain deficiencies. This research indicates that they can be made good thanks to Freire’s approach to education. Freire’s approach to education comprise a number of key elements, which can be divided into five groups, viz his views on power and empowerment; ethical-religious elements; consciousness and action; dialogue; educational practice; and education and the community. The research indicates that these elements can compensate for the deficiencies in restorative education. Freire’s approach and a number of connected approaches such as education for social justice, critical pedagogy and the doctrines of Mohlomi, can be combined in an integrated approach to education, referred to as integrated healing education. In the penultimate part of the research, the principles of integrated healing education are utilised to develop a practice-orientated implementation framework. The framework is discussed in two sections: the fields of implementation, viz the learned and lived curricula, and the implementation process through action research. The research concludes with a summary, limitations of the study, and recommendations.
Tirisodikgoka le tirisodikgoka ya kwa sekolong di baka tlhakatlhakano mo baaging ba Aforikaborwa. Mekgwa ya ga jaana ya go fedisa dikhuduego e ikaegile ka dithata, maitsholo a a siameng le molebo wa kotlhao, mme go bonala e sa nonofa. Maikemisetso a patlisiso eno e ne e le go batlisisa melebo e e farologaneng ya go samagana le tirisodikgoka ya kwa sekolong le go tlhama letlhomeso la tsenyotirisong la molebo wa sekolo sotlhe go samagana nayo. Patlisiso e dirilwe go ya ka sekao se se golaganeng sa ikholoji. Go lokolotswe megopolo ya "tirisodikgoka" le "tirisodikgoka ya kwa sekolong" ka ntlha ya fa gantsi e tlhakatlhakanngwa le megopolo ya "dithata" le "maitsholo a a siameng". Sebedi sa ntlha sa megopolo se dintlhadintsi mme di gona mo magatong otlhe a sekao se se golaganeng sa ikholoji. Se akaretsa tirisodikgoka ya batho bongwe ka bongwe, tirisodikgoka ya setlhopha le tirisodikgoka e e rulaganeng. Tirisodikgoka ya kwa dikolong e tlhagelela ka dipopego tse di farologaneng, go akaretsa badipisi le digongwana. Patlisiso eno e farologanya magareng ga tirisodikgoka e e laolegang ya kwa dikolong – e e mo legatong la tlhotlheletso la mo sekolong – le tirisodikgoka e e tsamaisegang kwa dikolong – e e tswang kwa ntle ga sekolo. Patlisiso e bontsha gore ditsela tse go samaganwang le tirisodikgoka ya kwa dikolong ka yona ga jaana ga di lebelele dikamano tse di senyegang ka ntlha ya tirisodikgoka, poelano magareng ga modiri le motshwasetlhabelo, le ditlhokego tsa motswasetlhabelo. Go tlaleletsa foo, ga di tshwaele mo tsamaisong ya tirisodikgoka ya kwa dikolong e e rulagantsweng. Molebo wa pusetso ke molebo wa fa gautshwane o o theilweng mo bosiamising jwa pusetso mme o akaretsa ditiragatso tsa pele ga tiragalo. Gonne o tsamaisiwa ke dintlhatheo mme o theilwe mo dikamanong, dipuisano, pusetso le poelano, o ka nna mosola thata mo ntweng kgatlhanong le tirisodikgoka ya kwa dikolong. Thuto ya pusetso e akaretsa mekgwa ya pele ga tiragalo le ya go tsibogela tiragalo e tshwana le tsereganyo ya motswasetlhabelo-molatofadiwa le dipuisano tsa ditlhopha. E tota baamegi ba sekolo ba ba laolwang ke dintlhatheo go na le tlolomolao. Le gale, thuto ya pusetso e na le makoanyana a a rileng. Thutopatlisiso eno e bontsha gore a ka baakanngwa ka molebo wa ga Freire wa thuto. Molebo wa ga Friere wa thuto o na le dikarolo di le mmalwa tsa botlhokwa, tse di ka aroganngwang ka ditlhopha tse tlhano, e leng, megopolo ya gagwe malebana le dithata le maatlafatso; dintlha tsa maitsholo-tumelo; temogo le tiragatso; puisano; tiragatso ya thuto; le thuto le baagi. Patlisiso e bontsha gore dintlha tseno di ka emela makoa a a mo thutong ya pusetso. Molebo wa ga Freire le melebo e mengwe e le mmalwa e e golaganeng e tshwana le thuto ya tshiamiso ya loago, thuto e e rutang barutwana go sekaseka dithata le kgatelelo le ditumelo tsa ga Mohlomi, di ka kopanngwa mo molebong o o golaganeng wa thuto, o o bidiwang thuto e e golaganeng e e alafang. Mo karolong ya pele ga ya bofelo ya patlisiso, go dirisiwa dintlhatheo tsa thuto e e golaganeng e e alafang go tlhama letlhomeso la tsenyotirisong le le theilweng mo tiragatsong. Letlhomeso le tlhalosiwa mo dikarolong tse pedi: lephata la tsenyotirisong, e leng kharikhulamo e e ithutilweng le e e tshetsweng, le tirego ya tsenyotirisong ka patlisiso ya tiragatso. Patlisiso e konosetsa ka tshobokanyo, ditekanyetso tsa thutopatlisiso, le dikatlenegiso.
Educational Foundations
Ph. D. (Philosophy of Education)