published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Call number: LD2668 .T4 1986 W43 / Master of Science / Chemistry

A Thesis Submitted to the Faculty of Science, University of the Witwatersrand , Johannesburg for the Degree of Doctor of Philosophy / The Phalaborwa Complex, northeastern Transvaal, South Africa, consists of the main body of clinopyroxenites and subordinate phoscorite, carbonatite and syenite which is surrounded by numerous pipe-like bodies of syenitic compositions and rare clinopyroxenites. Clinopyroxenites of the main complex are characterized by cumulus textures formed by separation and accumulation of coprecipitating clinopyroxene, apatite and phlogopite. Potassium feldspar is an intercumulus phase in feldspathic pyroxenite. "Inch-scale" layering of clinopyroxene, apatite and phlogopite formed as in situ cumulus layering near the outer contact of the complex early in the cooling of the magma. Breccias of monomineralic assemblages such as glimmerite and massive pyroxenite reflect breaking up of early formed rocks by magmatic currents. Clinopyroxenes from clinopyroxenites are characterized by Fe/(Fe+Mg) = 0.07-0.29, low T i 02 (0.00-0.25%), A 120 3 (0.00-1.63%), N a 20 (0.00-1.06%), and Cr, and high Wo component and Sr. Micas from pyroxenites have Fe/(Fe+Mg) = 0.12-0.28, low T i 02 (0.17-1.73%) and have reverse and normal pleochroism and increasing A1 with increasing Fe/(Fe+Mg). Mineral compositions among feldspathic, massive and micaceous pyroxenites overlap; no zonation of the complex from outer contact inward is discernible with respect to the Fe and Mg content. However, phlogopites in "inch-scale" layering have low Fe/(Fe+Mg) of 0.12 and have reverse pleochroism due to F e 3+ entry into the Al-deficient tetrahedral site. Micas from phoscorite and carbonatites have reverse pleochroism, Fe/(Fe+Mg) = 0.05-0.58, low T i 02 (0.00-0.84%) and decreasing A1 with increasing Fe/(Fe+Mg). Olivines range from F o79 to F o91 and have very low Ni content (<0.06% N i O ) . Olivines interpreted as xenocrysts have Fo 84 to F o 8 7 . One of the olivine xenocrysts has an NiO content of 0.29%. Minerals from carbonatites have initial 87S r / 86Sr ratios of 0.70393-0.70623 and 0.71022 and minerals from clinopyroxenites have values of 0.71152-0.71242. Smallscale inhomogeneities exist within samples. Postcrystallization processes can account for variations within samples, but cannot account for variations within a rock type or for raising initial 87S r / 86Sr ratios of pyroxene from 0.7039 to 0.7115. Magmas forming pyroxenites and some carbonatites were generated in a high Rb/Sr mantle from isotopically distinct sources. Hence, liquid immiscibility and differentiation are not viable mechanisms for relating these rocks to one another. Mixing of magmas and assimilation of crust may account for isotopic variations within a rock type. U-Pb dating of uranothorianite and baddeleyite from phoscorite and carbonatite yields an age of 2047+11/-8 m.y. Rb-Sr dating of phlogopites gives widely disparate apparent ages. Nine phlogopites yield an isochron of 2012 + 19 m.y. One sample of phlogopite gave ages of 1661-2360 m.y. in nine different determinations. Older micas may be present in the Phalaborwa complex. Based on the two methods, a best age of the Phalaborwa complex is 2030 + 18 m.y. Two of the syenite pipes, Kgopoeloe and Spitskop, show different levels of emplacement. Kgopoeloe is highly brecciated from a fluid derived from the syenite. Spitskop contains minor breccia and represents multiple injection of syenite. At Spitskop, inward crystallization of the second syenite forms a ring syenite and central syenite; both syenites have cumulus enrichment of minerals. Feldspathic pyroxenite of the Guide Copper Mine is cogenetic with the pyroxenites of the main complex and contains clinopyroxenes with oscillatory zoning. Fluctuations in f02 may be attributed to formation of an immiscible sulphide liquid. Multiple intrusion of the Phalaborwa Complex is proposed. Initial injection of potassic, probably ultrabasic, liquid formed the pyroxenites. A second intrusion of low-silica, carbonate-rich magma formed phoscorite and banded carbonatite. A third intrusion of carbonatite liquid formed the transgressive carbonatite. Magmatic, cumulus processes dominated the formation of the main complex. The syenites of Kgopoeloe and Spitskop are not cogenetic with rocks of the main complex. / AC2017

Nós estudamos a dinâmica do operador de renormalização atuando no espaço de pares (?, t), onde ? é um difeomorfismo e t ? [0, 1], interpretados como aplicações unimodais ? o qt, onde qt(x) = -2t|x|? + 2t - 1. Estabelecemos cotas complexas a priori para pares suficientemente renormalizáveis com combinatória limitada e então a utilizamos para mostrar que quando o expoente crítico ? está próximo de um número par, o operador de renormalização tem um único ponto fixo, o qual é hiperbólico e possui uma variedade estável de codimensão um que contém todos os pares infinitamente renormalizáveis / We study the dynamics of the renormalization operator acting on the space of pairs (?, t), where ? is a diffeomorphism and t ? [0, 1], interpretated as unimodal maps ? o qt, where qt(x) = -2t|x|? + 2t - 1. We prove the so called complex bounds for sufficiently renormalizable pairs with bounded combinatorics. This allows us to show that if the critical exponent ? is close to an even number then the renormalization operator has a unique fixed point. Furthermore this fixed point is hyperbolic and its codimension one stable manifold contains all infinitely renormalizable pairs

This thesis reports the results of investigations carried out into the composition of the saturate and aromatic unresolved complex mixtures (UCMs) in crude oils. It is divided into two sections. Section A reports on studies of the saturate UCM and Section B reports on studies of the aromatic UCM. UCMs are mixtures of very large numbers of compounds of low individual abundances, hence structural information on individual components is difficult or impossible to obtain using conventional GC or GC-MS techniques. The investigations reported in this thesis used a combination of GC-MS techniques (Section A) and oxidations of UCMs followed by GC-MS characterisation of the oxidation products (Section B) to develop a more detailed picture of the structures of components of the saturate and aromatic UCMs. UCMs are present in all crude oils, and may account for the vast majority of the material present in heavily weathered or biodegraded oils. An understanding of the types of compounds present may have a bearing on the refining processes an oil is subjected to, as well as assessing its potential environmental and toxicological effects.Single branched C(subscript)18 isomers were prepared to establish the chromatographic behaviour and mass spectral fragmentation patterns of open chain compounds with ethyl-, propyl-, butyl- and pentyl- substituents. All open chain structural isomers with a single n-alkyl branch larger than methyl in the range C(subscript)10 to C(subscript)20 were identified at each carbon number in a series of crude oils of varying ages, source types and depositional environments. Also, C(subscript)21 to C(subscript)25 structural isomers containing an ethyl branch were identified in all of these samples. This represents a total of 163 compounds. These monoalkylalkanes comprise approximately 3 % of the alkanes in these oils, with the n-alkanes (35-60 %) and ++ / methylalkanes (10 %) being the most abundant compound classes present. Isoprenoids, alkylcyclohexanes and other branched and/or cyclic alkanes make up the remainder of the material.Rock samples from a sedimentary sequence of Late Cretaceous age were analysed for ethylalkanes using GC-MS techniques. In the less mature samples, 3- and 5-ethylalkanes were in higher abundance relative to the other isomers at odd carbon numbers from C(subscript)17 to C(subscript)23. In the more mature samples, this odd preference was no longer apparent. Several other low maturity sediment samples were analysed and found to have a similar ethylalkane distribution to the shallow sample from the sedimentary sequence. A mature crude oil which was also analysed exhibited a distribution similar to the deeper sample from the sedimentary sequence. Tetralin pyrolysis of a low maturity lignite sample yielded only the 3- and 5-substituted ethylalkanes, providing supporting evidence that the initial odd preference is the result of defunctionalisation of specific natural product precursors containing a 3- or 5-ethylalkyl structural moiety. With increasing maturity this preference is diluted by input of ethylalkanes without preference. A mechanism involving acid-catalysed rearrangement of n-alkenes to form monoalkylalkanes is proposed to account for the loss of preference in ethylalkane relative abundances.Investigations into the composition of aromatic unresolved complex mixtures were conducted by oxidising the total aromatic fraction of a moderately biodegraded crude oil (biodegradation level 4) using potassium permanganate. This reagent cleaves the alkyl substituents attached to aromatic rings between the alpha and beta carbons and oxidises the alpha carbon to a carboxylate group. A biodegraded crude oil was chosen because the majority of the resolved components have been removed by biodegradation, ++ / leaving a complex mixture of compounds almost completely unresolved by gas chromatography. The oxidation product was separated into dichloromethane-soluble monocarboxylic acids (both aliphatic and aromatic) and water-soluble polycarboxylic acids (aromatic only). GC-MS analysis of these oxidation products gave the proportions of monosubstituted:disubstituted:trisubstituted:tetrasubstituted monoaromatic rings as 29:59:12:0.1, of which from one to three substituents were carboxylic acid groups with the remainder of the substituents being unoxidised methyl groups. Of the disubstituted monoaromatic oxidation products, 53 % were dicarboxylic acids with the most sterically hindered 1,2-substitution pattern. This observation was interpreted as evidence for the presence of significant amounts of naphthenoaromatic systems such as tetralins and indanes in the crude oil aromatic fraction. Analysis of the permanganate oxidation products also enabled a quantitative measure of the proportion of methyl substituents to be made. It was found that methyl groups accounted for a significant proportion of the alkyl substituents attached to aromatic systems. Of the disubstituted monoaromatic oxidation products, 59 % had a methyl group as one of the substituents, while of trisubstituted monoaromatic systems, 41% had one methyl and 37 % had two methyls. Compounds containing a biphenyl carbon skeleton comprised 3 % of the aromatic oxidation products, with isomers containing from one to four substituents of which one was a carboxylic acid group and the remainder were unoxidised methyls. This indicates that biphenyls containing more than one alkyl (>C(subscript)1) substituent were not present. Of the monosubstituted biphenylcarboxylic acids, the ratio of ortho:meta:para substituted isomers was 0:65:35, which correlates well with literature reports of the relative abundances of methylbiphenyl ++ / isomers, and suggests that the overall distribution of all monosubstituted biphenyls has not been significantly affected by biodegradation to level 4.The monoaromatic, diaromatic and triaromatic fractions of the same biodegraded crude oil (level 4) were separately treated with ruthenium tetroxide, which cleaves aromatic rings so that the ring carbon bearing the substituent is oxidised to become the carbonyl carbon of a carboxylic acid. These oxidation products represent the alkyl moieties that were attached to aromatic rings in the initial crude oil aromatic fractions. Identification of these alkyl side chains provides an insight into the nature of the components of the aromatic crude oil UCM. The oxidation products were separated into dichloromethane-soluble monocarboxylic acids, which were subsequently reduced to monodeuterated hydrocarbons for characterisation using gas chromatography-mass spectrometry (GC-MS) techniques, and water-soluble dicarboxylic acids which were analysed as dimethyl esters. n-Alkanes, methylalkanes, alkylalkanes, alkylcyclohexands, methylalkylcyclohexanes, isoprenoids and bicyclic alkanes were identified in the monodeuterated hydrocarbon samples derived from all three aromatic fractions. Most of these compounds had carbon skeletons strikingly similar to those observed in the saturate fractions of unbiodegraded crude oils, with the only differences being the addition of a carbon from the aromatic ring, and the presence of a deuterium atom attached to that carbon. Because the electron-withdrawing nature of carboxylic acid groups prevents further aromatic ring oxidation, numerous aromatic monocarboxylic acids were also identified in the acidic products of the oxidation of the crude oil diaromatic and triaromatic fractions. These included C(subscript)1 to C(subscript)3 alkyl-substituted benzoic acids derived from compounds containing a biphenyl ++ / or phenylnaphthalene structural moiety, as well as omega-phenylalkanoic acids with chain lengths up to C(subscript)11, derived from compounds in which two aromatic systems are connected by an alkyl chain. The main components of the dicarboxylic acid oxidation products of all three aromatic fractions were alpha, omega-dicarboxylic acids and alkylcyclopentane-dicarboxylic acids and alkylcyclohexane-dicarboxylic acids, with phthalic acids also present in the oxidation products of the diaromatic and triaromatic fractions. The observation that 1,5-pentanedicarboxylic acids and 1,6-hexanedicarboxylic acids were the only alpha, omega-dicarboxylic acids in the oxidation products of the crude oil monoaromatic fraction, and were present in high abundance relative to other alpha, omega-dicarboxylic acids in the oxidation products of the diaromatic and triaromatic fractions indicated that substituted indanes and/or tetralins were quantitatively important constituents of the overall crude oil aromatic fraction. This finding is supported by the results of the analysis of the mass spectra of the crude oil aromatic fractions.These studies of aromatic UCMs have provided new insights into the origins of the aromatic components of petroleum. The presence of a pronounced odd-over-even predominance in the C(subscript)25, C(subscript)27, and C(subscript)29 monodeuterated n-alkanes (CPI = 1.07), which corresponds to the odd-over-even predominance observed in the n-alkane components of unbiodegraded crude oils from the same basin, suggests that the n-alkyl side chains and the n-alkanes have a common source. Evidence is presented to support the hypothesis that the n-alkylaromatics are formed in part by geosynthetic processes involving alkylation of aromatic systems by electrophilic species such as carbocations and acylium ions formed from carboxylic acids. This hypothesis is then extended to ++ / explain the formation of other groups of compounds, including aromatic systems with isoprenoidal-, methylalkyl- and monoalkyl-branched side chains. Because isoprenoids, methylalkanes and alkylalkanes are well-known components of petroleum, these results suggest that these alkylaromatic components of petroleum may share a common source with the corresponding alkane components. It is suggested that aromatic unresolved complex mixtures arise due to the very large number of structurally related compounds present, which are formed by geosynthetic processes such as alkylation of aromatic rings.

While rheological and microstructural complexities have posed tremendous challenges to researchers in developing first principles models and simulation techniques that can accurately and robustly predict the dynamical behaviour of polymeric flows, the past two decades have offered several significant advances towards accomplishing this goal. These accomplishments include: (1). Stable and accurate formulation of continuum-level viscoelastic constitutive models and their efficient implementation using operator splitting methods to explore steady and transient flows in complex geometries, (2). Prediction of rheology of polymer solutions and melts based on micromechanical models as well as highly parallel self-consistent multiscale simulations of non-homogeneous flows. The main objective of this study is to leverage and build upon the aforementioned advances to develop a quantitative understanding of the flow-micro-structure coupling mechanisms in viscoelastic polymeric fluids and in turn predict, consistent with experiments, their essential macroscopic flow properties e.g. frictional drag, interface shape, etc. To this end, we have performed extensive continuum and multiscale flow simulations in several industrially relevant bulk and free surface flows. The primary motivation for the selection of the specific flow problems is based on their ability to represent different deformation types, and the ability to experimentally verify the simulation results as well as their scientific and industrial significance.

In this study, we used different ways to synthetize four-coordinate zinc(II) and nickel(II) complexes with optically active Schiff base offering N2S2 coordination, i.e. N,N'-Bis(2-thiobenzylidene)-l,2-(R,R)cycholhexyl- enediaminatozinc(II) (1) and N,N'-Bis(2-thiobenzylidene)-l,2-(R,R)cychol- hexylenediaminatonickel(II) (2). We obtained the crystal structure of 2 and the pyridine adduct of 1, N,N'-Bis(2-thiobenzylidene)-l,2-(R,R)cycholhexylenediaminopyridylzinc(II) (1¡DPy). Coordination geometry around Zn atom in 1¡DPy is a distorted trigonal bipyramid. These structures were compared with the N2O2 stuctural analogues reported in the literature. We hope these chiral complexes can make contribution to the enzyme model studies in the future.

Tri(2-thiophenyl)phosphine (P(C6H4-2-SH)3,PS3) was designed at 1989. Recently chemists use this ligand for enzyme models because it provides rich sulfur environment. Some chemists use PS3 to synthesize novel metal complexes. This thesis deals with the synthesis and structural discussion of germanium and tin complexes bearing PS3 ligands. Reactions with different metal source all yield novel structures. Reaction of GeCl4 with PS3 gives supramolecular structures with continuous £k-£k interaction. Similar reaction with GeCl3Me gives crystals in optically active form in stead of the usual optically inactive racemic form. Reaction with SnCl4 gives six-coordinate dimmeric tin complex (Sn(OMe)(PS3))2 with bridging methoxyl group and thiolate group (from PS3). Reactions using SnCl3Et or SnCl3Bu as metal sources followed by sublimation (140oC , 10-2torr) give reductive elimination products with alkyl groups transferred onto sulfur atom. These two structures are similar in morphology but different in skeletal arrangement.

In our previous studies on modeling methyl transfer protein, Ada protein, we found that zinc complexes of tri(2-thiophenyl)phosphine (PS3), (A), have similar methyl transfer behavior as its biological counter part. In order to probe the role of zinc in methylation process, we used tin and cadmium in model study to compare their chemistry relative to that of zinc. We found that all three metal complexes have similar chemistry and assume similar dimeric anion structure. For example, [Cd(PS3)]22-(1) and [Cd(SiPS3)]22-(2) have been successfully characterized crystallographically to possess the same structure as zinc dimer (A). However , in attempt to crystallize the tin analogue, the accidental oxidation product [SnIV(OH)2(SiPS3)]2, (5), was obtained. Its crystal structure gave clue to the mechanism of oxidation of the original tin dimer. The reactions with alkylating reagent of (1) have been compared with those of zinc dimer (A), and we found that the metal (Zn or Cd) center causes the dimers to produce different degree of methylation products toward different alkylating reagents. For the reactions with CH3I, the different degree of methylation between Cd and Zn dimers shows that the presence of zinc center has higher methylation selectivity and weaker reactivity.

We have successfully used the cadmium ion with (2-thiophenyl)phenylphosphine(PS2) or Bis(3-trimethylsilyl-2-thiophenyl)phenylphosphine(SiPS2) to synthesize [(PS2)Cd(TMEDA)](2) and [(SiPS2)Cd(TMEDA)](4) that were structurally similar to [(PS2)Zn(TMEDA)](1). We also obtained a series of zinc complxes [NEt4][(PS2)Zn(SC6H5)](6), [NEt4][{[(PS2)Zn](SC6H11)[(PS2)Zn]}](7) and [NEt4][(PS2)Zn(SCH2C6H5)](8) with systematically varied thiolates. From studying of the methylation reactions of these complexeswith methyliodine or trimethylphosphate, we found that the metal center(zinc or cadmium), ligand(PS2 or SiPS2) or the net charge (neutral ornegative) can influence the reaction time, selectivity of reaction site ormechanism. The zinc complexes (6), (7), and (8) are capable of completingthe catalytic cycle of mthylation-demethylation and hence a good model for related enzyme system.