La préparation efficace d’une nouvelle famille de sels de 1,3-bis(aryl)-4,5-dihydroimidazolium non symétriques comprenant un groupement encombrant hexafluoroisopropylmethoxy en position para- ou ortho- sur l’un des substituants N-aryle a été développée. De nouveaux sels d’imidazolium contenant un substituant fluoroalkyle en position ortho d’un des substituant aryle ont aussi été synthétisés. Ces sels sont d’excellents précurseurs de carbènes N-hétérocycliques qui ont permis l’accès efficace à une série de nouveaux complexes carbéniques du ruthénium à ligands NHC non symétriques. La méthode repose sur la génération in situ du carbène par traitement des sels d’imidazolium avec le potassium hexamethyldisilazide suivie d’un échange du ligand tricyclohexylphosphine à partir des complexes de Grubbs et Hoveyda de première génération. L’activité de ces nouveaux complexes a été étudiée sur des réactions modèles intra- et intermoléculaires de métathèse des oléfines. Il a été montré que la plupart des complexes synthétisés ont de bonnes activités catalytiques en fermeture de cycle à partir du diallylmalonate d’éthyle et en métathèse croisée de l’allylbenzène avec le 1,3-diacetoxybut-2-ene. Leurs performances sont comparables à celles des catalyseurs de Grubbs et Hoveyda de seconde génération, avec toutefois quelques différences dans les étapes d’initiation. Les effets structuraux et électroniques des ligands NHC non symétriques sur la réactivité des nouveaux complexes du ruthénium ont été étudiés. En particulier, il a été montré que les catalyseurs de type Hoveyda porteurs de ligands monosubstitués par un groupement fluoroalkyle en position ortho d’un des substituant N-aryle présentent une initiation très rapide dans les réactions de métathèse croisée. Au contraire, les complexes porteurs d’un groupement donneur alkyle ont montré une activité catalytique très faible, comme par exemple le complexe porteur d’un ligand (tert-butyl)NHC qui s’est révélé inerte à la fois en fermeture de cycle et métathèse croisée. Les complexes porteurs d’un ligand NHC symétrique avec deux groupes hexafluoroisopropylmethoxy ont des activités catalytiques nettement inférieures à leurs homologues non symétriques, révélant ainsi la forte influence de l’absence de symétrie du ligand carbène NHC dans l’activité catalytique des complexes. / An efficient approach to a new family of unsymmetrical 1,3-bis(aryl)-4,5-dihydroimidazolium salts comprising bulky hexafluoroisopropylmethoxy group in para- or ortho-position in one of the N-aryl substituents has been developed. New imidazolinium salts with fluoroalkyl-containing mono-ortho-aryl substituent at one of the nitrogen atom have also been synthesized. It was found that these imidazolinium salts are effective NHC precursors and provided an efficient access to a series of new ruthenium carbene complexes with unsymmetrical fluorinated NHC ligands. The method involves in situ generation of the carbene via treatment of the starting salts with potassium hexamethyldisilazide and subsequent ligand exchange reaction with PCy3-containing first generation Grubbs and Hoveyda complexes. The catalytic activity of the new complexes has been investigated on model reactions of intra- and intermolecular olefin metathesis. It was found that most of the synthesized complexes exhibited high activity in cyclization of diethyl diallylmalonate and in cross metathesis of allyl benzene with 1,3-diacetoxybut-2-ene. Their performance has proved to be comparable with commonly used second generation Grubbs and Hoveyda catalysts, with sometimes some differences in the initiation step. Structural and electronic impact of fluorinated unsymmetrical NHC on reactivity of new ruthenium complexes has been studied. In particular, it was revealed that Hoveyda type catalysts with mono-ortho-aryl substituted NHC ligands have demonstrated very high initiation rate in CM reactions. On the contrary, catalysts with more donating N-alkyl NHCs have displayed low activity; for instance, the N-tert-butyl substituted complex has proved to be absolutely inert both in RCM and CM reactions. Symmetrical ruthenium carbene complexes bearing NHC ligands with two hexafluoroisopropylmethoxy group in para-positions of N-aryl moieties are significantly inferior in reactivity with respect to their asymmetric counterparts showing the strong influence of the desymmetrization factor on catalytic activity.

Since the development of the understanding that the electron distribution within a molecule is chiefly responsible for its properties and behavior, factors influencing this charge distribution have been of interest to scientists. The chemical reactivity of a molecule, the physical properties, and to a large extent, structure and geometry, are all functions of the electron distribution. This study examines the issue of electronic structure from two points of view, each of them focussing on a specific component within the molecules studied. In the present work, the effects of the highly polar carbonyl group on spectroscopic parameters and physical behavior are investigated. An additional area of study is the effect of fluorine substitution on the energy levels of some halogenated ethylenes. The specific parameters examined are the ionization potentials, the absorption frequencies, and the energies of a class of excited states known as molecular Rydberg states. It was during the study of these halogenated ethylenes that the observations leading to the carbonyl compound investigations were made, so that the two areas examined are connected both experimentally and chemically.

Aujourd’hui, une large part des métaux utilisés par l’industrie provient généralement des mines. Certains, dits stratégiques, pourraient présenter un risque d’approvisionnement voire d’épuisement des ressources naturelles. Ces métaux sont généralement utilisés dans des processus dispersifs, et se retrouvent répartis de façon inégale, avec d’autres métaux, dans des matrices toujours plus complexes, ce qui rend leur récupération couteuse en termes de procédés et d’énergie. Que ce soit pour des raisons stratégiques, économiques ou sociétales, il apparait que le recyclage des métaux est amené à devenir une activité importante dans le futur. L’approche hydrométallurgique, et en particulier l’extraction-séparation liquide-liquide, est une technique adaptée et éprouvée à ce jour pour répondre au recyclage des métaux. Ce travail de thèse s’intéresse au développement et l’étude de systèmes moléculaires fluorés pour l’extraction et la séparation de métaux par une approche liquide-liquide. La modularité de la partie fluorée de ce type de système moléculaire permet l’étude des diverses interactions (complexations, supramoléculaires) importantes d’un point du vue fondamental dans l’extraction liquide-liquide de métaux. De plus, leurs propriétés physico-chimiques (miscibilité,…) permettent d’envisager le design de procédés innovants dans le domaine de la séparation liquide-liquide, comme la mise en œuvre de systèmes tri-phasiques. Pour cela, deux séries de malonamides fluorés avec des espaceurs de taille variable, entre la tête complexante et le groupement perfluoré, ont été synthétisés. La modulation par l’espaceur de l’effet inductif des chaines perfluorées sur les propriétés physico-chimiques des extractants et sur la complexation d’un métal a été étudiée. De même, l’influence de certains paramètres d’extraction comme la charge en extractant, en acide et l’influence du diluant ont été caractérisés. La comparaison avec les ligands homologues hydrogénés a été effectuée, et les limites des différents systèmes établies. Une série de phosphates de trialkyles a également été étudiée et appliquée à un système tri-phasique d’extraction liquide-liquide. Des résultats préliminaires valident de manière encourageante l’approche choisie. / A large part of the metals used by the industry is still coming from mines. Some metals, called strategic metals, may encounter a supply risk or even a total depletion of natural resources. They are usually used in dispersive way which make their recovery complicated, costly and energy intensive since they are in unequal amount, with other metal, in ever more complex matrices. Whether for strategic, economic or societal reason, the metal recycling is about to become an important industry in a near future. Hydrometallurgical processes, and liquid-liquid extraction in particular, are a robust technic giving answer to some of the recycling challenge. Our aim was to develop and study some fluorinated system for the extraction and the separation of metal through liquid-liquid approach. The tenability of the fluorinated part of these system allow the study of multiple interaction (complexation or supramolecular ordering) important in a fundamental point of view in liquid-liquid extraction. Physical and chemical properties such as their miscibility allow the development of new processes in the solvent extraction field such as triphasic liquid extraction system. To this end, two series of fluorinated malonamides with various spacer length between the complexing head and the fluorinated moiety were synthetized. The modulation, through the spacer, of the inductive effect of the fluorinated chain on the physical and chemical properties of the extractant and the complexation of the metal was studied. The influence of various extraction parameters such as the concentration in extractant, the acid and the diluent were characterized. The comparison of these malonamides with their hydrogenated homologues was done and the limits of these systems established. A family of trialkylphosphate was developed and apply to a triphasic extraction system. Preliminary results confirm the approach.

A la lumière de la bioaccumulation potentielle relative à la longueur de la chaîne fluorocarbonée, la duplication en chaines courtes constitue une technique intéressante dans la conception de nouveaux matériaux à très faible potentiel de biopersistance. Ainsi, nous avons utilisé cette méthode pour préparer de nouveaux matériaux tensioactifs et polymères conçus avec des chaînes courtes fluorées et évaluer l’influence des paramètres structuraux sur les propriétés physico chimiques de ces composés. L’évaluation des propriétés de surface des tensioactifs ont donné d’intéressantes valeurs aussi bien pour la tension de surface !!!! que pour la concentration micellaire critique (CMC) et la densité moléculaire adsorbée (Amin). La comparaison des propriétés de surface a permis de montrer, que les tensioactifs bicaténaires avec deux chaînes courtes fluorées C4F9 ou C6F13 peuvent égaler, voire dépasser les performances d’un monocaténaire à chaîne longue C8F17 réputé bioaccumulant. Deux populations d’agrégats ont été mises en évidence par la technique de la diffusion de la lumière en mode dynamique (DLS) et par microscopie électronique à transmission (TEM). Des monomères contenant deux segments fluorés ont été synthétisés. Les polymères correspondants ont ensuite été déposés par électropolymérisation et les propriétés de surface des films ont été étudiées. Des films superhydrophobes et oléophobes ont été obtenus avec le polymère PEDOT-2C4,4 à chaînes courtes du fait de nanoparticules uniformément réparties à la surface. Les performances des matériaux conçus avec deux chaînes courtes fluorées ouvrent des perspectives dans la lutte contre la bioaccumulation avérée des longues chaînes perfluorées. / In the light of the potential bioaccumulation relative to the length of the fluorocarbon chain, duplication short chains is an interesting technique in the design of new materials with very low biopersistance. Thus, we used this method to prepare novel surfactants and polymeric materials designed with fluorinated short chains and assess the influence of structural parameters on the physicochemical properties of these compounds. The evaluation of surface properties of surfactants gave interesting values for both surface tension !!!!, critical micelle concentration (CMC) and the molecular density adsorbed (Amin). Comparison of surface properties have shown that double-tailed short chains surfactants with two fluorinated C4F9 or C6F13 can match or exceed the performance of a single-tailed long chain C8F17 deemed bioaccumulant. These surfactants gave two aggregate populations identified by the technique of dynamic light scattering (DLS) and TEM images (transmission electron microscopy). Fluorinated monomers containing two segments were synthesized. The corresponding polymers were then deposited by electropolymerization and the films were studied. Oleophobic and superhydrophobic films were obtained with the PEDOT-2C4,4 polymer short chains because nanoparticles uniformly distributed on its surface. Performance materials designed with two short chain fluorinated open perspectives in the context of the fight against bioaccumulation proven long perfluorinated chains.

No description available.

Produced since the 1950’s, per- and polyfluoroalkyl (PFASs) substances are persistent, bioaccumulative and toxic compounds that are ubiquitous in the environment. Being proteinophilic with a tendency to partition to protein-rich tissues, PFASs have been found in human serum worldwide and in wildlife with a predominance of long-chain perfluoroalkyl carboxilic acids (C7-C14 PFCAs) and perfluoroalkyl sulfonic acids (C6-C9 PFSAs). Due to rising concern regarding their hazardous properties, several regulatory actions and voluntary industrial phase-outs have been conducted since early 2000s, shifting the production towards other fluorinated alternatives. This thesis explores the human exposure to long-chain PFASs and their alternatives using different modelling methods and aims to 1) link comprehensively the past and current industrial production with the human body burden and 2) assess the potential hazardous properties of legacy PFASs replacements, on which information is very limited. In Paper I, the historical daily intakes in Australia and USA were reconstructed from cross-sectional biomonitoring data of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) andperfluorohexanesulfonic acid (PFHxS). The results indicate that humans experienced similar exposure levels and trends to PFOS and PFOA in both regions, suggesting a common historical exposure possibly dominated by consumer products. The model could not be fitted to PFHxS concentration in serum. In Paper II, the relative contribution of indirect (i.e. subsequent metabolism of precursors into legacy PFASs) versus direct exposure was evaluated on occupationally exposed ski wax technicians. The indirect exposure contributed by up to 45% to the total body burden of PFOA. In Paper III, the physicochemical properties, the persistence and the long-range transport of fluorinated alternatives were predicted using different in silico tools. Findings suggest that fluorinated alternatives are likely similar to their predecessors, in terms of physicochemical properties and environmental fate. Finally, Paper IV compares the toxic potency of PFOS, PFOA and their alternatives as a function of external and internal dose. While alternatives are less potent than their predecessors when considering the administered dose, they become similarly potent when the assessment is based on levels in the target tissue. This thesis demonstrates that pharmacokinetic models are effective tools to comprehensively reconnect the body burden to the exposure of phased-out chemicals. More importantly, the studies on fluorinated alternatives raise the necessity to provide more information and data on the potential hazard of these novel and emerging products. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.</p>

Le travail présenté dans ce mémoire de thèse porte sur la préparation de nouveaux nanocomposites polystyrène-argile en utilisant des argiles modifiées par divers tensioactifs cationiques polymérisables fluorés. Des systèmes de référence ont aussi été envisagés en utilisant des tensioactifs classiques de structure proche de celles des surfmers (surfmers et tensioactifs hydrocarbonés) et ce, afin de mettre en évidence le rôle joué par le groupement polymérisable et l’atome de fluor sur la structure et les propriétés des nanocomposites obtenus. Les propriétés de surface des tensioactifs ont été étudiées en termes de CMC, tensions de surface et enthalpies de micellisation de Gibbs afin d’évaluer le comportement en solution de ces tensioactifs. Ces tensioactifs ont été par la suite utilisés pour modifier une montmorillonite sodée via un processus d’échange cationique. Les organoargiles ainsi obtenues ont été caractérisées par IR, ATG et DRX. Les données DRX obtenues sont en faveur d’un alignement de la majorité des surfmers fluorés en bicouche La préparation des nanocomposites polystyrène-argile contenant diverses quantités d’organoargiles variant de 1 à 15% en utilisant la technique de polymérisation radicalaire en masse ou en solution, a montré l’effet positif de l’introduction d’une chaîne fluorée et d’une fonction polymérisable sur la stabilité thermique des nanocomposites. Des morphologies exfoliées ont été obtenues pour la majorité des nanocomposites fluorés préparés. Une relation structure-propriétés de surface et propriétés thermique a été établie sur la base des analyses ATG, DRX et TEM/MEB. / The work presented in this thesis focuses on the preparation of new polystyrene-clay nanocomposites using fluorinated polymerizable cationic surfactants as modifiers. Reference systems have also been proposed using conventional surfactants of similar structure than surfmers. The main objective is to highlight the role of the polymerizable group and the fluorine atoms on the structure and the properties of the obtained nanocomposites. The surface properties of surfactants were studied in terms of CMC, surface tensions and Gibbs enthalpies of micellization to evaluate the solution behavior of these surfactants. These surfactants were subsequently used to modify a sodium montmorillonite via cation exchange process. The resultant organoclays were characterized by IR, TGA and XRD analysis. XRD data are in favor of an alignment of the majority of fluorinated surfmers to form a bilayer structure while conventional surfactants tend to form a pseudotrimolecular layer. Determination of surfmer reactivity ratios by NMR was used to predict the behavior of these derivatives in radical copolymerization with styrene. Preparation of polystyrene-clay nanocomposite containing various amounts of organoclays from 1 to 15 wt% by radical polymerization process in bulk or solution, showed the positive effect of the introduction of fluorinated chain and polymerizable functional group on thermal stability of nanocomposites. Exfoliated morphologies were obtained for the majority of the fluorinated nanocomposite. A structure-surface and thermal properties relationship was established on the basis of TGA, XRD and TEM / SEM analysis.

This thesis describes approaches towards the synthesis of 20-deoxybryostatins and 20,20-difluorobryostatins. Towards the 20-deoxybryostatins, a route previously developed within the group was followed with a protecting group change designed to prevent problems encountered with a late-stage deprotection. To this end, (R)-pantolactone was transformed through to dimethyl (4S,6R,8R)-[4-(para-methoxybenzyloxy)-10-hydroxy-6,8-O-isopropylidine-3,3-dimethyl-2-one] phosphonate which was subsequently subjected to a Horner-Wadworth-Emmons condensation with (5R,E)-6-(4-methoxybenzyloxy)-5-triethylsilyloxy-3-(2’-triisopropylsilyloxyethylidene)hexanal. The reactions of the resulting enone through to the advanced intermediate allyl [(4R,6R)-6-((S)-2’-(4-methoxybenzyl)oxy-5-{(2’’S,6’’R)-6’’-(4-methoxybenzyloxymethyl)-4’’-[2-triisopropylsilyloxyeth-(Z)-ylidene]-tetrahydropyran-2’’-yl}-3,3-dimethyl-4’-oxopentyl)-2,2-dimethyl-1,3-dioxan-4-yl]-acetate are described, and this compound corresponds to a C1-C16 northern bryostatin fragment. A synthetic route to 20,20-difluorobryostatins was begun by the synthesis of three 3,3-difluoro-2-hydroxytetrahydro-4H-pyrans which started from an indium-mediated coupling of 3-bromo-3,3-difluoro-1-propene with an aldehyde. A strategy was employed which culminated in the preparation of 3,3-difluoro-2-hydroxy-2-(3-methylbut-1-en-3-yl)-4-(E)-methoxycarbonylmethylenetetrahydro-4H-pyran which corresponds to a C16-C23 20,20-difluorobryostatin southern fragment. Of particular interest is the selectivity observed in the reaction of α,α-difluoroketones with a stabilised Wittig reagent. The indium-mediated coupling was extended to include the first example of the coupling of a 2-alkyl substituted bromide.

A CuI fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2] (1), was previously shown to form a trinuclear copper–dioxygen species with a {Cu3(3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. A significantly expanded kinetic and mechanistic study of TOC4F9 formation is reported using stopped-flow spectroscopy. The TOC4F9 complex performed catalytic oxidase conversion of para-hydroquinone (H2Q) to para-benzoquinone (BQ) and hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first tri-copper species to perform tyrosinase (both monooxygenase and oxidase) chemistry. As opposed to 1, when K+ is fully encapsulated in {K(18C6)}[Cu(OC4F9)2] (4), O2 was not reduced under identical conditions. To study the effects of both alkali cation and the degree of encapsulation on reduction of O2, derivative complexes were synthesized with Na+ (16), {Na(DME)}+ (17), {Na(15C5)}+ (18), {K(15C5)}+ (19), {K(15C5)2}+ (20), Cs+ (21), {Cs(18C6)}+ (22), and {Cs(18C6)2}+ (23). Reduction of O2 was found to be encapsulation-dependent, and cation size was also determined to affect the chromophore observed. These results suggest that cation…F/O interactions between the CuI complexes assemble aggregates that are required to form reactive {Cun−O2} species. However, catalytic oxidation of H2Q to BQ and sub-stoichiometric oxidation of DBP to catecholate occurred regardless of whether a {Cun−O2} intermediate was detected, suggesting that a reactive species may self-assemble in the presence of substrate in all complex derivatives unable to reduce O2. A series of heteroleptic mixed phosphine/alkoxide 3d complexes was designed to evaluate PPh3 as a protecting group. Complexes of the form [(Ph3P)2M(OC4F9)2] (M= Fe (24), Co (25), Ni (26), Zn (27)) and [(Ph3P)2M(pinF)] (M= Co (31), Ni (32), Zn (33)) were prepared and characterized, along with related complexes with non-reactive L-donors for comparison, [(DME)Fe(OC4F9)2] (28) and [(Ph3PO)2M(OC4F9)2] (M= Fe (29), Ni (30)). Dimeric [Fe2(-O)(OPPh3)2(OC4F9)4] (36) was isolated after O2 reactivity with 24, and 28 and 29 were able to generate intermediate species capable of both oxidation of H2Q to BQ and oxygen atom transfer of thioanisole to methyl phenyl sulfoxide. The choice of fluorinated ligand influences O2 reactivity with CoII (25, 31), but not for NiII (26, 32). Related dimeric compounds [Co2(pinF)2(THF)4)] (34) and [Zn2(pinF)2(THF)2)] (35) were also isolated.

A series of fluorinated LiCoO2 compounds, LiCoO2−xFx with x = 0.05 − 0.65, were synthesised by both a sol-gel and a solid-state method. The sol-gel method utilises LiNO3 and Co(NO3)2.6H2O as Li and Co sources respectively, water and 1-butanol as solvent for the fluoride precursor LiF, and citric acid as the chelating agent. The prepared materials were compared using pXRD, SEM, Raman, TG and DTA analyses. pXRD revealed a secondary phase appearing at x= 0.25 in materials prepared by the sol-gel method and as early as x= 0.08 in materials prepared by the thermal solid-state method. Materials prepared by the thermal solid-state method required higher temperatures and longer times than materials prepared by the sol-gel method. The results showed that more fluorine can be incorporated in the LiCoO2 structure by the sol-gel than the solid-state method. The secondary phase was identified as lithium oxydifluoride, LiCoOF2. Relatively pure material with stoichiometry could be prepared by both methods. The space was determined as either 𝐶2 or 𝑃1 and the unit cell dimensions for the two alternatives are reported. This secondary phase has been reported in the literature, but had not been positively identified at the time of submission of this dissertation. Keywords: fluorinated LiCoO2; LiCoO2−xFx; sol-gel fluorination; solid-state fluorination; lithium oxydifluoride. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted