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Polyesters are an important class of polymers in many applications ranging from common-use objects—such as packaging containers, clothing, and upholstery—to more advanced applications, such as lightweight strength materials in construction, electronics, and automotive parts. Poly(ethylene terephthalate) (PET), a semicrystalline aromatic polyester, is commercially the most common and widely used polyester. However, the inability to reuse polyesters such as PET over multiple reprocessing cycles in the same application remains a challenge due to the susceptibility of the polymer to thermal, hydrolytic, and oxidative degradation during melt processing. The various degradation modes result in a drop in molecular weight, loss of key physical properties, and release of volatile compounds. Furthermore, the vast issue of plastic accumulation and pollution in diverse ecosystems, landfills, and waste streams underscores the burgeoning need to create a closed loop—responsible materials management from the cradle to the grave—through these materials' continual reuse and recycling. Additionally, most feedstock monomers used in polyester synthesis primarily come from fossil fuels. Fossil fuel extraction processes release gases and particulate matter that adversely affect health, climate, and the environment, so finding alternative sources for polyester monomers is paramount. This dissertation addresses key polyester challenges by designing and synthesizing alicyclic polyesters. First, we synthesized a series of alicyclic polyesters using various ratios of two regioisomers of a previously unexplored alicyclic monomer, bicyclohexyldimethanol (BCD). We learned from this alicyclic polyester series that we could tailor properties such as morphology and elongation while raising the glass transition temperatures (Tg) and lower melting temperatures (Tm) of the polymers based on the regioisomer composition. Furthermore, the regioisomer that led to polymers with semicrystalline morphologies inspired us to apply it to PET as a copolymer, with the goal of increasing PET's stability under melt processing conditions by lowering Tm. Next, we synthesized a series of alicyclic copolyesters with different BCD compositions in the polymer. The results showed that the presence of the alicyclic rings of BCD lowers the melting temperature and enhances the stability of the polymer in the melt compared to PET. These results directed us toward synergistically combining the benefits of alicyclic monomers with sustainable biobased monomers to enhance polyester properties, thereby decoupling fossil fuels from polymer feedstock production. Accordingly, we explored naturally ubiquitous, structurally diverse, and chemically modifiable terpenes present in the resin exudate of conifers. Specifically, we derived alicyclic diacid and diol monomers from the terpene verbenone and used them to synthesize a series of biobased alicyclic polyesters. The polymer series exhibited a range of morphologies, Tg's, as well as enhanced stabilities. The semicrystalline composition exhibited higher Tg and slightly lower Tm than PET while possessing exceptional stability in the melt over PET. / Doctor of Philosophy / Polyesters are important materials widely used today. They are very large molecules composed of a basic chemical unit linked together in a repeating fashion to make a long chain. The nature of the links between the basic units is referred to as an ester link, and materials are described as polyester when the number of these links is large. The applications of polyesters range from common-use objects—such as packaging containers, clothing, and upholstery—to more advanced applications in construction, transportation, and defense—such as body armor, seat belts, and lightweight strength materials and coatings in construction. The properties of its basic structural unit enable the wide breadth of applications of polyesters. A significant challenge that faces polyesters is the inability to reuse the material in the same application multiple times. The material must be reprocessed by melting at high temperatures to be reused. This melting breaks down the polyester chain, weakening the material and rendering it unsuitable for continued use. The need to reuse polyesters is an important area of concern because of the growing problem of plastic accumulation and pollution in diverse ecosystems and landfills. If these materials are continually reused, they will not accumulate as environmental waste. Furthermore, the basic starting unit that makes up polyesters largely comes from fossil fuels. Fossil fuel extraction processes release gases and particulate matter that adversely affect health, climate, and the environment. The issues of polyester breakdown in the melt and fossil fuel use to make the polyester can be addressed in two ways. First, reinforcing the polyester through changes to the basic structural unit can prevent the breakdown of the material when melted, thereby enabling its reuse over multiple cycles. Second, reducing the dependence on fossil fuels to make the basic structural unit of the polyester can be accomplished by using more renewable biobased sources instead. This dissertation seeks to address these two challenges. In the first approach, we investigate the effect of using a special cyclic structure in the polyester make-up to reinforce its stability when melted and enable its reuse. Next, we use plant materials to derive these unique structures to reduce the dependence on fossil fuels and mitigate the environmental, climate, and health effects of fossil fuel use.

Chemistry has been defined by some as an art, by others as a science and people have gone as far as dismissing it as pure alchemy. Overall, however, one cannot help but come to the conclusion that chemistry is a unique blend of all three. The work contained within this manuscript is an attempt to delve deep into the mysteries of but one type of transformation - a ¡¥simple¡¦ cyclisation step in which one couples two different moieties to form a cyclobutane ring with the aid of SmI2. There are two opposing forces of nature which control the outcome of this reaction, namely elimination and cyclisation and it is the contest between these two driving forces that ultimately decides the fate of these transformations. This work was born from previous attempts in RAU¡¦s laboratories to synthesise chiral cyclobutane derivatives from carbohydrates as well as the apparent discrepancies in two independent scientists¡¦ publications on the effect of SmI2 on reactions utilising 1,4-diketones. Hoffmann from Germany had managed to form 1,2-cyclobutanediols from a pinacol reaction promoted by SmI2 while Ghosh in India had experienced fragmentation products under similar conditions. The information contained herein provides a bird¡¦s eye view of cyclisation vs. fragmentation in 1,4-disubstituted compounds as well as an insight into how one might avoid or exploit the particular reaction pathways. The effects of various moieties in a ¡§ƒ×¡¨ disposition to the ketone have been investigated to obtain a broader understanding of the scope of the cyclobutane ring formation. These findings also provide the information necessary for effecting cyclobutane ring closures within the realm of carbohydrate chemistry. One will learn that the ¡¥geminal¡¦ effect is not the only efficacious method for the coupling of a ketyl radical and an activated alkene to form a four-membered ring. The thesis concludes with a strategic route towards the synthesis of a potential antiviral compound containing the cyclobutane substructure, originating from the simple sugar D-ribose. / Prof. D.B.G. Williams

Indirect nuclear spin-spin coupling constants in high resolution nuclear magnetic resonance (NMR) spectroscopy provide the most powerful method for determining conformations and structures of molecules in solution. The research described in this dissertation establishes the conformational and substituent dependencies of several new types of nuclear spin-spin coupling for use in structural studies. It was also of interest to determine the electronic factors which lead to the observed experimental trends. Geminal, vicinal, and four-bond carbon-carbon nuclear magnetic resonance coupling constants were studied experimentally with fifty carbon-13 enriched alicyclic compounds. Because of the small magnitudes of many of these coupling constants it ~vas necessary to modify existing Fourier transform NMR equipment to perform J-resolved two-dimensional NMR experiments. With the greater spectral resolution it was possible to determine 56 intercarbon geminal (²J(cc)), 107 vicinal (³J(cc)) and 26 four-bond (⁴J(cc)) coupling constants. These data represent the largest collection of ²J(cc), the only known data for ⁴J(cc), and the most accurate compilation of vicinal ¹³C-¹³C coupling constants. In combination with molecular orbital methods, the relevant conformational and substituent trends in each of these series were elucidated. Because of the great amount of interest in the importance of bridgehead interactions in "strained" molecules, a study is presented of coupling transmitted via nonbonded interactions between the bridgehead carbons in a series of l-substituted-bicycloalkanes. The two-dimensional Fourier transform methods were again used to obtain the experimental coupling constants and molecular orbital methods were used to determine the importance of the intercarbon bridgehead interactions on ¹H-¹H, ¹³c-¹H, ¹³C-¹³C, ¹³c-¹⁹F , and ¹H-¹⁹F coupling constants. In all cases the nonbonded interactions increased dramatically as the separation between the bridgehead carbons decreased. Further understanding of mechanisms of "through space" coupling were based on NMP. studies of the long range coupling constants (⁵J(HF) and ⁴J(HF)) in N-methyl-8-fluoroquinolinium halides. The X-ray structure of N-methyl-8-fluoroquinolinium chloride was determined in an attempt to calculate the observed ⁵J(HF) and ⁴J(HF). A selective population inversion mIR method was used to show that the sign of ⁵J(HF) in N-ethyl-8- fluoroquinolinium iodide is positive.

The well-defined ruthenium-carbene complexes reported by Grubbs and co-workers were the first ruthenium catalysts to show good activity and selectivity in metathesis of acyclic and cyclic olefins. Unfortunately the use of the Grubbs type catalysts is limited to the small scale synthesis of polymers and essential organic reactions, due to cost and instability of the catalyst at elevated temperatures. Some of the most successful Grubbs-type catalysts included hemilabile ligands. By releasing a free coordination site (the so-called "on-demand-open-site") for an incoming nucleophile, hemilabile ligands have the ability to increase the thermal stability and activity of a catalytic system, by stabilization of the transition metal centre. Previous studies indicated that the incorporation of a sterically hindered N and 0 chelating ligand increased the stability, activity and selectivity of Grubbs type complexes and increasing the electron density of the complex can influence the stability of a complex and therefore the catalytic performance. In this study alicyclic, bidentate N and 0 chelating ligands (16-19) were modelled in order to evaluate the hemilability of these ligands. The modelling was used as a comer stone from which the synthesis was conducted. Molecular modelling showed that of the four ligands identified only two (16 and 18) could potentially be hemilabile. 17 would rather form a transaunular ether compound. The modelling results were incondusive for ligand 19 and further investigation is necessary for this compound… / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2010.

The well-defined ruthenium-carbene complexes reported by Grubbs and co-workers were the first ruthenium catalysts to show good activity and selectivity in metathesis of acyclic and cyclic olefins. Unfortunately the use of the Grubbs type catalysts is limited to the small scale synthesis of polymers and essential organic reactions, due to cost and instability of the catalyst at elevated temperatures. Some of the most successful Grubbs-type catalysts included hemilabile ligands. By releasing a free coordination site (the so-called "on-demand-open-site") for an incoming nucleophile, hemilabile ligands have the ability to increase the thermal stability and activity of a catalytic system, by stabilization of the transition metal centre. Previous studies indicated that the incorporation of a sterically hindered N and 0 chelating ligand increased the stability, activity and selectivity of Grubbs type complexes and increasing the electron density of the complex can influence the stability of a complex and therefore the catalytic performance. In this study alicyclic, bidentate N and 0 chelating ligands (16-19) were modelled in order to evaluate the hemilability of these ligands. The modelling was used as a comer stone from which the synthesis was conducted. Molecular modelling showed that of the four ligands identified only two (16 and 18) could potentially be hemilabile. 17 would rather form a transaunular ether compound. The modelling results were incondusive for ligand 19 and further investigation is necessary for this compound… / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2010.

The purpose of this work was to investigate the reaction of allena and phenyl azide, in order to gain greater insight into the reaction of aryl azides with allenes.

A major purpose of this research was to investigate the mechanism of aryl azide addition to allenes. Much evidence has accumulated in support of a concerted mechanism for aryl azide additions to simple alkenes. Consistent with these findings, this addition is a symmetry allowed process. The analagous aryl azide additions to allenes have received little mechanistic study. The approach taken in this work was to probe the mechanism by using optically active 1,2-cyclonanadiene, observing the stereochemistry of the adduct formed upon addition of phenyl azide. Another goal was to investigate the isomerization of the phenyl azide-1,2-cylononadiene adduct, 10-phenyl-10,11,12-triaza-△ 11 -bicyclo [7. 3. 0] duodec-1-ene (7) to the previously unknown aromatic isomer 4,5-heptamethylene-1-phenyl-1,2,3-triazole (14).

At ~662 gigatonnes of carbon (GtC), marine dissolved organic matter (DOM) is the largest reduced pool of actively cycling carbon and nitrogen in the oceans1. Operationally defined as smaller than 0.1µm in size, this carbon reservoir comprises all non-living organic matter smaller than a bacterial cell and comprises organic colloids and molecules spanning as a continuum of sizes ranging from marine viruses and large macromolecules (e.g. DNA, enzymes) to small organic molecules (e.g. polymers and monomers)2. With deep apparent 14C-ages ranging between 4900-6400 ybp 3,4, marine DOM is anomalously old given timescales of global ocean ventilation (1000-1500 years). The great age of DOM has remained one of the most elusive lines of scientific inquiry in Chemical Oceanography for decades. The size and molecular composition of DOM has been shown to be a key variable in determining its biological reactivity (e.g. cycling rate) and long-term persistence in the deep ocean5,6. Despite the importance of DOM in the marine carbon and nitrogen cycles, we lack a detailed understanding of the molecular composition of DOM. Due to the high concentration of salts in seawater relative to DOM, it is difficult to analyze the molecular composition of seawater with conventional chemical- or size- fractionation methods without introducing bias (i.e. isolating only hydrophobic and/or high molecular weight DOM). In fact, it is commonly reported that >80% of DOM remains uncharacterized at the molecular level (e.g. not readily identifiable as an individual known biomolecule)5. Nuclear magnetic resonance (NMR) spectroscopy has been used as a tool for several decades to describe the composition of marine DOM isolates7. For example, 13C-NMR of major high molecular weight DOM functional groups at the molecular-level demonstrated that DOM is largely made up of reactive polysaccharides with low aromaticity compared to terrestrial DOM8. To date, all marine DOM NMR measurements have been made on size-fractionated DOM or chemically-fractionated (e.g. solid phase extracted) DOM isolates. In this thesis, I report the first Proton (1H) NMR composition of total seawater DOM from seawater samples collected from 10 stations in Baffin Bay aboard the CCGS Amundsen (2019). Samples were measured using 1H-NMR at uOttawa following a novel water suppression method established by Lam and Simpson9. The use of this method has allowed for the first molecular composition assessment of total seawater DOM to be measured (e.g. without any chemical or size fractionation). I report the % relative abundance of individual biomarkers and determine molar concentrations of two compound classes of interest. These results are shown in Ocean Data View section plots, and are listed within appendix tables, to provide a comprehensive depiction of the changing concentrations of dissolved organic carbon (DOC), total carbohydrates (TCHO), and carboxyl-rich alicyclic molecules (CRAM). In this thesis, I explore changes in the abundance of these unique DOM compound classes and discuss how the composition of DOM directly determines its bioavailability and thus cycling in Baffin Bay 5. The core objective of my thesis was to measure DOM concentrations for TCHO and CRAM, as well as to calculate the production and removal of these key DOM compounds in Baffin Bay due to either physical and/or biological processes. We found that the concentration of both TCHO and CRAM decreased with depth throughout Baffin Bay. This is consistent with previous work suggesting the rapid cycling of carbohydrates, however it contradicts the current paradigm of CRAM cycling. Our results indicate between 21-43% of CRAM produced in the surface is subsequently removed at depth. Rapid cycling of a surface CRAM population suggests that not all CRAM can be considered recalcitrant DOM We live in a time of unprecedented global change. The Arctic Ocean is warming at a rate at least four times faster than the global average10. The impact of a rapidly warming, freshening and increasingly acidified Arctic Ocean on the biogeochemistry of DOM remains unknown. It is imperative that more DOM research be conducted as early as possible in order to better understand these impacts and inform future research directions. The distribution and cycling of CRAM in Baffin Bay provide novel and fundamental knowledge of DOM cycling in a key Arctic region, but could also potentially occur throughout the global ocean. Such data will no doubt be of use in informing future iterations of Earth System Climate models seeking to forecast how the marine carbon cycle will respond to global change.