A dissertation submitted to the Faculty of Science for the degree of Master of Science University of the Witwatersrand, Johannesburg / It is well known that chlorinated organic compounds behave as highly toxic substances in the environment. Catalytic hydrodechlorination .... one of the more convenient approaches used to treat chlorinated organic substances with the aim of obtaining compounds with lower or null toxiciy. Further, the selective cleavage of the C-Cl bond plays a key role in processes related to the manufacture of fine chemicals. These reactions can be performed over noble-metal catalysts, either in the gas or liquid phase. (Abbreviation abstract) / Andrew Chakane 2018

Thesis advisor: Lawrence T. Scott / Chapter 1. The impact and growth of carbon nanotubes within the framework of nanotechnology is presented. Methods to produce single chirality nanotubes from template-mediated sources are evaluated. The concept of a nanotube endcap is introduced as a potential synthetic target toward the selective synthesis and growth of a single chirality carbon nanotube. Chapter 2. A modified synthesis of corannulene is presented, highlighting a selective imine based reaction protocol for the fuctionalization 4,7-dimethylacenaphthenequinone. Also reviewed is a cascade coupling approach toward the synthesis of corannulene, followed by an analysis of the thermochemistry of the two-component disconnection. Chapter 3. The synthesis of 6 different indenoannulated corannulene congeners derived from a single flash vacuum pyrolysis (FVP) is described. X-ray crystal structures for each indenoannulated corannulene are presented along with computational modeling. Spectroscopic comparison between observed and theoretical 1H NMR provides one of the largest complete and comparative data sets for a collection of PAHs. Chapter 4. The application of a palladium based indenoannulation reaction is presented as an alternative synthetic method to FVP. Heteroatom based derivatives of both tetraindenocorannulene and pentaindenocorannulene were both developed as potential solubilizing factors. The thermochemistry for each successive indenoannulation of 1,3,5,7,9-pentaphenylcorannulene leading to pentaindenocorannnulene has been calculated, providing an approximated energy landscape for the total transformation. Chapter 5. Several routes for the synthesis of 1,3,5,7,9-pentakis(2,6-dichlorophenyl)-corannulene are presented. The yield for this reaction has been improved through the use of a palladium based precatalyst. During this time we studied a five-fold palladium catalyzed borylation of corannulene using B2pin2. Finally development of a cascade coupling reaction towards a [5,5] SWNT endcap is highlighted by a 12 bond coupling reaction. Chapter 6. A nickel-promoted homo-coupling between the proximally situated aryl halides of 1,2,5,6-tetrakis(2-chlorophenyl)corannulene is used to complete the synthesis of diphenanthro[9,10-a:9′,10′-g]corannulene. X-ray quality crystal were grown of diphenanthro[9,10-a:9′,10′-g]corannulene, and the structure was solved. The crystals forms highly ordered arrays in a columnar fashion with each phenanthro segment aligned through a series of π - π stacking interactions. / Thesis (PhD) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

This thesis outlines work carried out over the past three years concerning the development of an experimentally simple, sustainable catalytic method for the functionalisation of pyridines by means of a zinc nitrate based Lewis acid. It encompasses reaction discovery and optimisation, determination of the scope of the method through nucleophile and substrate screens as well as investigations into the mechanism by which the reaction takes place. Chapter 1 gives a general overview of the industrial relevance of pyridine functionalisation as well as the synthetic methods for the synthesis of ring functionalised pyridines, covering traditional stoichiometric aromatic substitution methods, transition metal catalysed cyclisations, standard catalytic methods for the functionalisation of pyridines: Buchwald-Hartwig and Ulmann reactions, as well as a précis of some recent transition metal catalysed methods for C-H functionalisation of pyridines. It also reviews classical and transition metal catalysed methods for conjugate addition and Diels–Alder reactions of vinylpyridines. Chapter 2 involves reaction discovery for the use of Lewis acids for the activation of pyridines towards nucleophilic aromatic substitutions, reaction optimisations, kinetic investigations and an examination of the scope in substrates and incoming groups. Chapter 3 investigates the use of Lewis acids for the activation of vinylpyridines toward conjugate addition, reaction optimisations, investigations into scope of incoming groups and subsequent optimisation studies for each. The method is also extended to Diels–Alder cyclisations, for which the reaction is also optimised.

Versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications ranging from medicine to energy storage. To expand the design space for innovative cationic polymeric materials, I describe herein the development of a new class of functional polyelectrolyte based on the aromatic trisaminocyclopropenium (TAC) ion. The facile synthesis of a series of cyclopropeniumbased macromolecules via either the direct polymerization of functional monomers or a post-polymerization click reaction is demonstrated. To probe fundamental structureproperty relationships and understand technological implications of cyclopropenium polymers, a variety of materials were evaluated as gene delivery agents for cellular transfection and as ion conducting membranes. It was found that certain cyclopropenium polymers are biocompatible and efficient transfection agents, and that post polymerization functionalization chemistry enabled the straightforward screening of polymeric TAC derivatives. Furthermore, the thermal properties, local morphology, and dielectric response of a series of monomeric and polymeric TAC ionic liquids with different counter ions were characterized. It was found that the mechanism for ion transport depends on the nature of the ion pair, which can promote anomalously high conductivity at the calorimetric glass transition temperature. Finally, the synthesis of a new class of polyelectrolyte based on the cyclopentadienyl aromatic anion is described.

No description available.

No description available.

Faculty of Science School of Chemistry 9800165e govendor@aurum.wits.ac.za / Pyranonaphthoquinones are biologically important molecules found in a wide variety of bacteria, microbial fungi and plant species. Their biological activity is proposed to be a consequence of their ability to function as bioreductive alkylating agents. This class of compounds, which include monomeric and dimeric examples, contain the basic naphtho[2,3-c]pyran-5,10-dione skeleton, usually with substituents at the C-1 and C-3 positions of the pyran ring. The aim of the first part of the project was to develop a novel method for the synthesis of enantiomerically pure 5,8-dimethoxy-isochroman-4-ol, which will provide a handle for stereoselectively adding substituents to the C-1 and C-3 positions of the pyran nucleus. In the second part of the project we wished to attempt to synthesize the naturally occurring compound, cardinalin 3, the dimer of ventiloquinone L previously synthesized in the Wits laboratories. The synthesis of the enantiomerically pure isochromanol began with 2,5-dihydroxybenzoic acid, which was subjected to a diallylation followed by a Claisen rearrangement. The phenols were protected by a methylation reaction and the ester moiety was reduced to give (2-allyl-3,6- dimethoxyphenyl)methanol. It was then allylated to produce a suitable precursor for a one pot/two step ruthenium mediated isomerisation/ring closing metathesis reaction to produce 5,8-dimethoxy-1H-isochromene in an overall yield of 47%. It was converted to racemic 5,8-dimethoxy-isochroman-4-ol through a hydroboration-oxidation reaction in a yield of 84%. The separation of the enantiomers was achieved by acetylating the alcohol to form 5,8-dimethoxy-3,4-dihydro-1H-isochromen-4-yl acetate and then a lipase enzyme was used to stereospecifically deacetylate one enantiomer, while leaving the other enantiomer untouched. The second part of the dissertation discusses the progress towards the synthesis of cardinalin 3. This project began with the formation of the C-C biaryl axis starting from 1,3-dimethoxybenzene. The synthesis then continued with the diformylation of the biphenyl to give 2,2’,6,6’-tetramethoxy[1,1′-biphenyl]-3,3′-dicarbaldehyde. This was subjected to a Stobbe condensation and a Friedel-Crafts acylative cyclisation to produce diethyl [4,4′-diacetoxy-6,6′,8,8′-tetramethoxy-7,7′-binaphthalene]-2,2′- dicarboxylate. The synthesis will be continued in the PhD, using methodology previously developed for the formation of the monomer, as well as methodology developed here.

Petroleum hydrocarbons are emitted into the environment via natural and anthropogenic activities. Once emitted, these hydrocarbons can be transported globally, persisting and accumulating in aquatic ecosystems. In the Alberta oil sands region (AOSR), mining activities have significantly altered and polluted the surrounding aquatic and terrestrial environments with heavy metals and various petroleum hydrocarbons including polycyclic aromatic hydrocarbons (PACs). Though PACs have been tracked through time using dated lake sediment cores, separating natural and anthropogenic PACs can be difficult. In the Peace Athabasca Delta (PAD) this task is especially difficult as this region has been receiving annual inputs of naturally eroded bitumen throughout history. Petroleum biomarkers are unique petrogenic compounds (i.e. derived from petroleum) which may provide a secondary proxy to track mining impacts. This thesis investigated the impacts of mining activities on the AOSR and the PAD using two different proxies, PAC and petroleum biomarkers. These two regions were compared to reference lakes to the south and northwest of the Athabasca oil sands formation, in order to provide a natural signal, with minimal oil sands mining contamination. Historically deposited PACs and petroleum biomarkers were analysed in radiometrically dated lake sediment cores from the AOSR and the PAD, Alberta. Sediment profiles in the AOSR (Saline Lake) showed increases in PAC fluxes for both alkylated and parent compounds coeval with mining activities. Alkylated PAC fluxes in reference lakes (Mariana Lake and BM11) increased at the height of oil sands development (1990s). PAD lakes showed no statistical increase in PAC flux through time due to high levels of naturally eroded bitumen entering the system. Parent PAC diagnostic ratios, however, showed clear shifts from pyrogenic (primarily wood burning) in pre-development sediments to petrogenically derived PACs in modern sediments, in both AOSR and PAD lakes, coeval with oil sands development. Petroleum biomarker diagnostic ratios in Saline Lake and PAD lakes remained stable through time, indicating a clear current and historical petroleum signal originating from the AOSR. Reference lakes (Mariana Lake and BM11) showed the greatest change in petroleum biomarkers. Historically, these lakes had signatures uncommon of petroleum sources, however, in recent years petroleum inputs from mining development were revealed by these petroleum biomarkers. This study compared the historical trends of several petroleum hydrocarbons in lake sediment to the historical emissions of these petroleum hydrocarbons from oil sands mining operations. Notably, we show the potential for petroleum biomarkers to trace petroleum hydrocarbon contamination in the environment.

1 / Yue Sun

Two case studies are described where partially biodegraded petroleum residues were collected from the marine environment and analysed to investigate the changes in aromatic hydrocarbons with increasing biodegradation.The first of these studies, involved following the weathering of sea-floor residues from drilling discharges from an offshore petroleum exploration and production platform situated off the coast of North Western Australia. During operations, formation cuttings with adhering oil-based drilling muds were discharged into the ocean via a chute into approximately 125n1 of water, forming a substantial mound at the base of the platform. A suite of seabed sediments was collected from 16 sampling sites at various distances from the platform immediately following the cessation of drilling operations. The distribution of hydrocarbons in the sediment directly under tile cuttings chute was consistent with that found in drilling fluids formulated from a kerosene-like fluid. The samples from more remote sites exhibited the successive enhancement of an unresolved complex mixture relative to the n-alkanes, associated with tile presence of residues from petroleum biodegradation processes. In a subsequent sampling some three years later, a 10 cm core was retrieved from the cuttings pile and divided into 1 cm depth intervals. Samples within 6 cm of the surface of the cuttings pile contained biodegraded residues of the drilling mud, where the extent of biodegradation increased with decreasing proximity to the surface, most likely indicative of aerobic biodegradation. Biodegradation was less evident in the underlying sediments, where anaerobic conditions prevailed. / Analysis of the aromatic hydrocarbons in both sets of sediment extracts by using gas chromatography-mass spectrometry (GC-MS) revealed the successive depletion of alkylnaphthalenes, and due to the subtlety of changes in the extent of biodegradation, provided an excellent opportunity to examine the susceptibility of biodegradation towards the individual alkylnaphthalenes in the marine environment. Conventional GC-MS analysis of these mixtures is performed under chromatographic conditions where complete resolution of the mixture is not achieved and several isomers co-elute. The mass spectra of these co-eluting isomers may be so similar that one is unable to differentiate between them, and their abundance may therefore not be determined. Since each isomer has a unique infrared spectrum, however, the abundance of each individual isomer was determined by comparing the infrared spectrum of the co-eluting compounds with the spectrum of each of the isomers. To this end, techniques were developed for the application of direct-deposition gas chromatography - Fourier transform infrared spectroscopy (GCFTIR) to the analysis of the complex mixture of alkylnaphthalenes present in the petroleum. This technique was also extended to discriminate between individual alkylphenanthrene isomers, and to clarify the sorption behaviour of the dimethylphenanthrenes by mordenite molecular sieves. The identification of other compounds of geochemical significance in petroleum is also described. / Analyses of' the aromatic hydrocarbons in the contaminated sea-floor sediments using GC-FTIR enabled the unambiguous identification and quantification of each of the dimethylnaphthalene, trimethylnaphthalene and tetramethylnaphthalene isomers present in the samples, from which the relative extents of depletion of each with increasing extent of biodegradation were determined. It was apparent from the considerable differences in the observed susceptibility to biodegradation that a strong relationship exists between the compound structure and its susceptibility to biodegradation, with 1,6-disubstituted polymethylnaphthalenes being preferentially depleted relative to other isomers that lack this feature. The second case study involved tracking the fate (weathering) of hydrocarbons from an accidental release of condensate from a buried pipeline into intertidal coastal (mangrove) sediments in North Western Australia. Sediment samples were collected on nine occasions over a three-year period. Chemical analysis of the saturated and aromatic hydrocarbon components of the petroleum extracts revealed that both hydrocarbon fractions exhibited an increasingly biodegraded profile with increased residence time in the sediments. In a similar manner to the first case study, detailed analysis of the aromatic hydrocarbons using GC-FTIR techniques was performed to determine the depletion of individual alkylnaphthalene isomers with increasing extent of biodegradation. It was apparent that a relationship similar to that observed for the sea-floor sediments exists between the alkylnaphthalene structure and its susceptibility to biodegradation. / Changes in the distribution of methylphenanthrene and dimethylphenanthrene isomer mixtures were also studied and the susceptibility to biodegradation amongst these determined in a similar manner. These relative susceptibilities to biodegradation of the aromatic hydrocarbons were then related to the established hierarchy of susceptibilities of the saturated hydrocarbons, in effect providing a second parallel system for the assessment of the extent of biodegradation. Finally, a system of ratios calculated from the relative abundances of selected aromatic hydrocarbons was developed and used as indicators to differentiate between several crude oils that have been biodegraded to varying extents. These parameters also offer promise as indicators of multiple accumulation events in oil reservoirs where petroleum fluids biodegraded to differing extents are mixed.