This thesis investigates the synthesis, characterization, and optical isomerism of some cobalt (III) complex compounds.

No description available.

No description available.

Call number: LD2668 .T4 1965 S611 / Master of Science

Perfluorocarboxylates (PFCAs) are a class of anthropogenic compounds ubiquitously found in the environment. PFCAs and their precursors are largely manufactured by electrochemical fluorination (ECF) or telomerization. ECF products are mixtures of isomers with linear (70-80%) and branched perfluoroalkyl moiety. Telomerization does not produce isomer mixtures and is predominantly n-perfluorocarbons. This thesis examined the environmental fate and disposition of PFCAs from a relevant and novel perspective of industrial isomer signature. Potential influences of physical and biological properties of isomers on the environmental PFCA isomer pattern were investigated. Branched isomers were more water soluble than n-isomer, however, KOW did not indicate any appreciable differences among isomers. It is possible that the similarity in KOW is due to a balancing effect between elevated activity coefficients in both water and n-octanol. In fish and rats, the major branched isomers of ECF PFOA were eliminated faster than n-isomer. In comparison, PFOS isomer pharmacokinetics were indistinguishable. These findings highlight the need to understand underlying mechanisms mediating PFCA and PFOS isomer pharmacokinetics which may constrain extrapolation from animal-based models to humans. Environmental monitoring revealed PFCA isomers in both abiotic and biotic environment, in temperate regions and remote Arctic. Branched PFOA isomers were consistent with ECF production. In temperate regions, industrially produced ECF PFOA was expected to be a major source of these isomers, given its legacy and volume of production. In the Arctic, PFOA isomers consistent with an ECF signature were attributed to ECF perfluorooctylsulfonamides which likely undergo long range atmospheric transport and atmospheric reactions. The major difference in ECF signature between remote and temperate regions is the presence of ECF PFNA isomers compared to their absence in the Arctic. ECF PFNA is an impurity in ECF PFOA, comprising 0.2%. Input from a linear source, such as fluorotelomer compounds, was also suggestive as both PFOA and PFNA were >95% linear, much more than in technical ECF. Furthermore, longer chain ECF impurities do not account for the PFNA, PFDA, PFUnA, etc. in the Arctic.

Thesis presented for the degree of Magister Technologiae: Chemistry in the Faculty of Applied Sciences at the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY / The separation of isomers with similar chemical structures is one of the most difficult procedures in chemistry. This is because their physical and chemical properties are generally so similar that most of the common techniques are not successful. In such situations one employs host-guest chemistry, as a tool of separation technology. In this thesis three aromatic hydrocarbon host compounds 9,9’-bianthryl (H1), 9,9’-spirobifluorene (H2) and trans-2,3-dibenzoylspiro(cyclopropane-1,9’-fluorene) (H3) were investigated in terms of their selectivity towards heterocyclic aromatic compounds (pyridine, PYR; piperidine, PIP; morpholine, MOR and 1,4-dioxane, DIO), cyclohexanone derivative compounds (cyclohexanone, CYHA; 2-methylcyclohexanone, 2-MCYHA; 3-methylcyclohexanone, 3-MCYHA and 4-methylcyclohexanone, 4-MCYHA) and the xylene isomers (ortho-xylene, ox; meta-xylene, mx and para-xylene, px). The H1, H2 and H3 host compounds were combined with a series of the heterocyclic compounds and six inclusion compounds were formed: H1•MOR, H2•2PYR, H2•PIP, H2•MOR, H2•DIO and H3•PYR. In the second part the derivatives of cyclohexanone formed inclusion compounds with the hosts H1 and H2. The H1•2CYHA, H1•ANT, H1•0.5(2-MCYHA) and H3•CYHA structures were obtained. In the third part the H1 formed clathrates with ox and px; H2 and H3 only formed clathrates with px and ox respectively. The following four structures were obtained: H1•0.5ox, H1•0.5px, H2•0.5px and H3•ox and were analysed by single crystal X-ray diffraction (SCXD), powder X-ray diffraction (PXRD), proton nuclear magnetic resonance spectroscopy (1H-NMR), thermal gravimetry (TG) and differential scanning calorimetry (DSC). It wasconcluded that H2 discriminates between the four heterocyclic compounds as follows: PIP > MOR ≈ DIO ≈ PYR and this can be explained by the 1H-NMR results and the packing features. In analysis of the xylene isomers, it was found that the three hydrocarbon host compounds H1, H2 and H3 efficiently discriminate between the isomers by forming inclusion compounds. H1 enclathrates both ox and px but prefers the former. This can be explained in terms of the packing features and lattice energies. H2 and H3 only enclathrate px and ox respectively. It was concluded that host compounds with small conformational movements are potentially good in selective inclusion.

Rotaxanes are a class of compounds composed of two or more mechanically interlocked molecules. Mechanically planar chiral rotaxanes are a novel class of compound in that their chirality is due to the isomerism of a mechanical bond, as opposed to the covalent bonding of the individual components. We know of no method to synthesise enantiomerically pure samples of the mechanical isomers of a mechanically planar chiral rotaxane without resorting to advanced purification techniques. The lack of ready availability of these materials has hampered the full investigation of their properties and applications. Of particular interest are their properties as chiral reaction-spaces, such as ligands, organo-catalysts, and chiral resolution agents. This thesis addresses these issues by developing a chiral-auxiliary approach toward the synthesis of mechanically planar chiral rotaxanes whereby an intermediate pair of diastereomeric rotaxanes are synthesised and separated using reliable and scalable standard laboratory techniques. Cleavage of the chiral auxiliary allows for the synthesis of enantiopure mechanically planar chiral rotaxanes. Tuning the structure of the mechanically interlocked components as well as the reaction conditions allows for control over the diastereoselectivity during the mechanical bond forming step.

Perfluorocarboxylates (PFCAs) are a class of anthropogenic compounds ubiquitously found in the environment. PFCAs and their precursors are largely manufactured by electrochemical fluorination (ECF) or telomerization. ECF products are mixtures of isomers with linear (70-80%) and branched perfluoroalkyl moiety. Telomerization does not produce isomer mixtures and is predominantly n-perfluorocarbons. This thesis examined the environmental fate and disposition of PFCAs from a relevant and novel perspective of industrial isomer signature. Potential influences of physical and biological properties of isomers on the environmental PFCA isomer pattern were investigated. Branched isomers were more water soluble than n-isomer, however, KOW did not indicate any appreciable differences among isomers. It is possible that the similarity in KOW is due to a balancing effect between elevated activity coefficients in both water and n-octanol. In fish and rats, the major branched isomers of ECF PFOA were eliminated faster than n-isomer. In comparison, PFOS isomer pharmacokinetics were indistinguishable. These findings highlight the need to understand underlying mechanisms mediating PFCA and PFOS isomer pharmacokinetics which may constrain extrapolation from animal-based models to humans. Environmental monitoring revealed PFCA isomers in both abiotic and biotic environment, in temperate regions and remote Arctic. Branched PFOA isomers were consistent with ECF production. In temperate regions, industrially produced ECF PFOA was expected to be a major source of these isomers, given its legacy and volume of production. In the Arctic, PFOA isomers consistent with an ECF signature were attributed to ECF perfluorooctylsulfonamides which likely undergo long range atmospheric transport and atmospheric reactions. The major difference in ECF signature between remote and temperate regions is the presence of ECF PFNA isomers compared to their absence in the Arctic. ECF PFNA is an impurity in ECF PFOA, comprising 0.2%. Input from a linear source, such as fluorotelomer compounds, was also suggestive as both PFOA and PFNA were >95% linear, much more than in technical ECF. Furthermore, longer chain ECF impurities do not account for the PFNA, PFDA, PFUnA, etc. in the Arctic.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 53-55). Also available on the World Wide Web.

While chemical isomers typically have distinct properties, differentiating between them is often an analytical challenge, especially for mass spectrometric methods. Infrared multiple photon dissociation (IRMPD) spectroscopy and ion mobility spectrometry (IMS) can be useful in analysis of such isomeric compounds; however, experimental results alone do not directly provide in-depth structural information. In this thesis, computational chemistry is first used to explain experimental results and understand the conformational preference of the gas phase ions formed from the lithiation of cis-3, cis-4 and trans-4 hydroxyproline isomers and then used in a predictive manner to evaluate IRMPD spectroscopy and IMS as potential paths forward for the characterization of isomeric dye species. Finally, theoretical methods are used to begin to understand the dissociation pathways of lithiated hydroxyproline isomers in the gas phase, which is ongoing.