No description available.

Thesis (Master of Applied Science in Chemistry)--Cape Peninsula University of Technology, 2018. / The prediction of the single crystal structure that will form due to the combination of two or more compounds to form a multicomponent crystal is one of the important areas of research in crystal engineering. Since these compounds display different properties when combined as a single crystal, knowledge of synthesis and design of the resulting compound is essential. The formation of a multicomponent crystal, such as a salt or a cocrystal generally depends on the complementarity of the functional groups present on both components. This means that basicity and acidity of the functional groups present on the selected compounds need to be considered. This study investigated salts and cocrystals of 3-chloro-4-hydroxyphenylacetic acid (CHPAA) using the ΔpKa rule. The calculated ΔpKa values were recorded and correlated with the experimental analysis in predicting the outcome of the crystallisation experiments ie. salt or cocrystal formation. This was further confirmed by the analysis of the C-O bond lengths found in the crystal structures. Salts were obtained by combinations of CHPAA with several organic bases (co-formers) such as diethylamine, dibutylamine, 2-aminopyridine, 2-amino-4-methylpyridine, 2-amino-6-methylpyridine and 4-dimethylaminopyridine. The calculated ΔpKa values were within the range of salt formation. Furthermore, the experimental analysis also showed that all resulting compounds were salts. Cocrystals were obtained by reactions of nicotinamide, isonicotinamide, phenazine and 4,4’-bipyridine with CHPAA. Again, the calculated ΔpKa values predicted cocrystals as the new solid forms. Experimental analysis carried out also confirmed cocrystal formation. For all resulting compounds, the comparison of intermolecular interactions as well as supramolecular synthons were reported. All compounds were synthesised by slow evaporation techniques using various organic solvents and characterised by single crystal X-ray diffraction, powder X-ray diffraction, thermal analysis and Fourier transformer infrared spectroscopy. From the structural analysis, it was found that all resulting structures displayed strong N-H•••O and O-H•••O intermolecular interactions including weak interactions of C-H•••Cl, C-H•••O and C-H•••π for a few of the structures. Furthermore, comparison of the crystal structures showed that no packing arrangement similarity existed between the compounds.

Thesis (Ph.D.)--Boston University / Due to the necessity of recovering uranium from reactor fuels, a number of separation methods have been investigated in recent years. Of these, the method of solvent extraction has proved to be a practical one. Long chain symmetrical phosphine oxides have been shown to extract uranium and a number of other metals under different conditions. It was the object of the present investigation to establish the nature of the species resulting from uranyl nitrate-R3Po (R =alkyl group) interaction. The two phosphine oxides selected for the study were: (i) Tri-n-octylphosphine oxide (TOPO) and (ii) Tris(2-ethylhexyl)phosphine oxide (TEHPO). An attempt was made to obtain pure TEHPO. Though the attempt has not met with complete success, yet significant conclusions concerning the stoichiometry and relative stability of the uranyl nitrate-TEHPO complex could be drawn. [TRUNCATED]

Quan Ming Wang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 119-133). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

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Abstract not available

The overall aim of the research presented in this thesis was to evaluate the importance of arbuscular-mycorrhizal ( AM ) colonization of plants in management of saline lands. Some aspects of application of AM fungi in revegetation of saline lands are also reported. Effects of AM pre-inoculation on mycorrhiza-responsive and non-responsive plant growth and establishment were evaluated under glasshouse conditions. The advantages of mycorrhizal fungal inoculation in increasing plant salinity tolerance and establishment in saline conditions were related to the responses of host species to AM fungi. Pre-inoculation with Glomus intraradices increased plant growth, nutrient uptake and establishment of mycorrhiza responsive Trifolium subterraneum in saline conditions, but non-mycorrhiza responsive Festuca arundinacea did not get growth benefits from AM in saline conditions. The main mechanism underlying increased plant growth and establishment in saline conditions in mycorrhiza responsive plants was increased plant nutrient uptake, particularly phosphorus ( P ) , at an early growth stage. The improvement could be explained by higher soil volume exploration by hyphae and / or roots, faster nutrient uptake and microbial changes in the soil rhizosphere. AM inoculation and P application effects on salinity tolerance were compared in Trifolium subterraneum. Application of P increased plant growth and salinity tolerance in saline conditions, but AM inoculation increased nutrient uptake and plant salinity tolerance more efficiently than P application. Effects of salinity on AM colonization of chenopods were investigated under glasshouse conditions. Salinity had no effects on AM colonization of Atriplex nummularia, but AM inoculation increased plant growth and nutrient uptake. The growth improvement was attributed to benefits from low AM colonization, and changes in bacterial community composition in the rhizosphere. Roles of AM fungi in influencing P leaching from soil were investigated in experiments with repacked cores under both non-saline and saline conditions. Increased plant size via AM inoculation significantly decreased P leaching in the soil profile under both non-saline and saline conditions in low P soils. Increased root volume and extension external hyphal network were the main effects of AM fungi in increasing plant size under saline and non-saline conditions, which led to scavenging more P and depleting more soil available P, thereby decreasing P losses via leaching. Application of P increased plant size and decreased P leaching, but on the other hand increased soil available P and decreased AM colonization. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.

Graduation date: 1966

Ph.D.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves.