Thesis--Ph. D., University of Hong Kong. / Typewritten.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (Habilitationschrift)--Technische Hochschule "Fridericiana" zu Karlsruhe, 1906. / Includes bibliographical references (p. 104).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 43-48).

The orientational order of the methylene segments adjacent to the head group in the lamellar liquid crystalline phase of potassium palmitate/D₂0 was investigated using multinuclear magnetic resonance. Previous studies had shown that the orientational order near the soap--water interface decreased with decreasing temperature, contrary to intuition. To investigate this phenomenon, three isotopically substituted species of palmitic acid were synthesized: palmitic acid-d₃₁, 1-¹³C-2,2-H₂- palmitic acid-d₂₉, and 2,2,3,3-H₄- palmitic acid-d₂₇. These compounds were treated in two complementary fashions: the acids were dissolved in the liquid crystal 4 - (octyloxy) - benzoic acid (p - OOBA) and the corresponding potassium salts were dispersed in D₂0 at a constant water concentration. Dipolar and quadrupolar couplings were obtained from the ¹H, ¹³C, and ²H nmr spectra of these molecules, in nematic and lamellar liquid crystalline phases, as a function of temperature. In a parallel study, nmr spectra of acetic, propionic, and butyric-2,2 - d₂ acids dissolved in p - OOBA were recorded. In order to observe ¹H - ¹H dipolar couplings, a two dimensional spin echo (π/2 - t₁/2 - π - t₁/2 - echo) was necessary to remove heteronuclear dipolar couplings to the chain deuterons. A refocussing pulse applied simultaneously to the spins allowed observation of the heteronuclear ¹H - ¹³C dipolar couplings in the carbon 13 labelled compound. The complete orientational order matrix of the alpha methylene segment of potassium paImitate/D₂0 and of palmitic acid/p - OOBA was determined from the dipolar and quadrupolar couplings. As the temperature is decreased from 110°C to a temperature just above the gel-liquid crystalline phase transition (45°C), the orientation of the methylene segment of potassium palmitate is rotated by 3° towards a configuration in which the first C - C bond is parallel to the bilayer normal. This is in direct agreement with a previous model, the Abdollal model of lipid - water interaction, in which the decrease in orientational order was postulated to be a strictly geometric effect arising from electrostatic interactions of the lipid with the water. A mean field equilibrium statistical mechanical model, based on the Samulski Inertial Frame Model, was developed to simulate the experimental dipolar and quadrupolar nmr couplings. In potassium palmitate, electrostatic interactions, approximately constant at higher temperatures, increase dramatically as the phase transition is approached. In contrast mean field steric repulsive forces remain constant over the entire temperature range studied. This evidence also supports the Abdollal model of lipid - water interaction. The electrostatic interaction was shown to be of greater importance in the orientational ordering of the solutes in the liquid crystal than in potassium palmitate and this was attributed to intermolecular H - bonding between solute and p - OOBA. The ordering of the head group of carboxylic acids dissolved in p - OOBA was demonstrated to be remarkably similar regardless of the chain length of the solute. / Science, Faculty of / Chemistry, Department of / Graduate

The γ-o-substituted-phenylparaconic acids were prepared by a method patterned after that of Fuson. These paraconic acids were prepared in good yield. A re-investigation of the Perkin and Fittig methods of preparing γ-phenylisocrotonic acid was carried out without success. The synthesis of γ-o-halophenylisocrotonic acids by thermal, and catalyzed decarboxylation of γ-o-halophenylparaconic acid, have been carried out in good yield. An effective catalyst, optimum temperature and reaction period of decarboxylation of the γ-o-halophenylparaconic acids have been.determined. Infrared absorptions have characterized the γ-o-halophenylisocrotonic acids formed to be in the stable trans form. Cyclization of γ-o-halophenylisocrotonic acids was accomplished by isomerization of the trans acid to cis acid by ultra-violet irradiation, followed by refluxing in the presence of sodium acetate and acetic anhydride. The subsequent hydrolysis of the acetylatednaphthol afforded the 5-halo-l-naphthol.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 52-54).

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Pyridine ring analogs of the aromatic amino acids phenylalanine and tyrosine were synthesized and studied in microbiological and mammalian systems.

The physicochemical characteristics of seven cold-pressed flaxseed oils sold in New Zealand were investigated for their fatty acid composition, tocopherol composition, moisture and volatile matter, free fatty acids, chlorophyll pigments, unsaponifiable matter, total phenolic acids and flavanoids, and colour. The seven cold-pressed flaxseed oils exhibited significant variations in their physicochemical characteristics. Quality of the oils in terms of oxidative stability was also investigated. Four oils were found to be within the limit of good stability oil indices, measured in terms of peroxide value, p-anisidine value, conjugated dienoic acids, specific extinction in ultraviolet spectrum, acid value and food oil sensor readings (to indicate total polar compounds). The role of minor constituents in the oxidative stability of two selected oils with different levels of fatty acid composition and minor constituents was investigated. Pan heating at 150�C caused loss of tocopherols, plastochromanol-8, phenolic acids, chlorophyll pigments, β-carotene and lutein and changes in the fatty acid composition. The pan-heated oils exceeded the limit of good stability oil indices using the measurement mentioned above except for acid value. The addition of α-tocopherol to the oils did not provide enhanced protection to the oils in accelerated aging of oil tests at 60�C. It was most likely that phenolic acids present in the oils played a dominant role in the oxidative stability of the oils. Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using a commercially available immobilized lipase B from Candida antarctica (Novozym 435) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using Electrospray Ionization-Mass Spectroscopy (ESI-MS). Separation and isolation of two classes of lipophilized products was also achieved using a solid phase extraction method developed in this study for further investigation into the structure-free radical scavenging activity. Free radical scavenging activity was determined using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method. The polarity of the solvents proved important in determining the free radical scavenging activity of the substrates. Ferulic acid showed much higher free radical scavenging activity than cinnamic acid, which had limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the free radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the free radical scavenging activity. Although, compared with the lipophilized cinnamic acid product, the activity was lower. The free radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyldioleoylglycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient free radical scavenger than lipophilized cinnamic acid. Lipase-catalyzed transesterification of flaxseed oil with cinnamic and ferulic acids using Novozym 435 was conducted to evaluate whether the lipophilized products provided enhanced antioxidant activity in the oil. The lipophilized products were identified using ESI-MS and were examined for their free radical scavenging activity toward DPPH in ethanol and ethyl acetate. Ferulic acid showed the highest free radical scavenging activity among all substrates tested while cinnamic acid had negligible activity. The effect of esterification of cinnamic acid and ferulic acid with flaxseed oil was similar to that with triolein. Lipophilized ferulic acid was a better free radical scavenger as compared with lipophilized cinnamic acid and extended the naturally-occuring antioxidant capacity of the flaxseed oil. Lipophilized cinnamic acid did not provide much enhanced radical scavenging activity in the flaxseed oil as the presence of natural hydrophilic antioxidants in the oil had much greater radical scavenging activity. It may still be useful for unsaturated oils with a small amount of natural antioxidants in them. Lipophilized cinnamic and ferulic acids showed higher free radical scavenging activity when tested in a less polar solvent (ethyl acetate) whereas ferulic acid showed better activity in a more polar solvent (ethanol). These results indicate that the choice of solvent for the DPPH assay is critical in evaluating the free radical scavenging activity of substrates of differing polarity, and support previous observations by other authors that the solubility of an antioxidant in relation to the site of oxidation is an important factor for consideration in the use of antioxidants.