Thesis (Ph.D.)--George Mason University, 2009. / Vita: p. 131. Thesis director: Estela Blaisten-Barojas. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computational Sciences and Informatics. Title from PDF t.p. (viewed June 10, 2009). Includes bibliographical references (p. 125-130). Also issued in print.

Thesis (M. Phil.)--University of Hong Kong, 1990.

Thesis (Ph. D.)--University of Oregon, 2004. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 173-178). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2005. / Includes bibliographical references (leaves 179-182).

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Chapter One describes the mechanism of acid-catalysed hydrogen-exchange in methylpyrroles. Using buffer solutions it was found that this reaction is subject to general acid catalysis, confirming an A-S[sub]E2 mechanism. It was also found that the rate of hydrogen-exchange at the β-position of pyrrole was similar to that at the alpha-position. This seems to conflict with the known preference for alpha-substituted products obtained under 'synthetic' experimental conditions. However, both these findings have been rationalised in terms of the electron densities and the localisation energies prevalent in the pyrrole ring. The mechanism of the reaction between 4-dimethylamino-benzaldehyde (DMAB) and pyrroles in acid solution (Ehrlich's Reaction) is described in Chapter Two. This consists of a rate-determining electrophilic attack of O-protonated DMAB on unprotonated pyrrole followed by a rapid loss of a water molecule to give the highly-coloured conjugated product. The activating effect of methyl groups at various positions on the pyrrole ring on this reaction was also determined. Acid-catalysed hydrogen-exchange in methylthiophens is the subject of Chapter Three. In contrast to the situation found in pyrroles, the rate of exchange at the β-position of thiophen is much slower than at the alpha-position. An explanation for this is found in the difference in electron densities found in the two ring systems. The activating effect of methyl groups at various positions on the thiophen ring on the exchange reaction was also studied. It was found that these effects were not additive. The activating parameters for the exchange reactions at the alpha- and β-positions were also calculated and discussed. In Chapter Four the practical difficulties encountered in the quantitative determination of the clinically important pyrroles porphobilinogen and cryptopyrrole are discussed. A series of reagents were used in an attempt to improve on the present colourimetric test employing DMAB. It was found that the measurement of cryptopyrrole under acidic conditions is straightforward using DMAB, 2,4,6-trimethoxybenzaldehyde (TMB) or 2,4-bis(dimethylamino)benzaldehyde (BDMAB). In contrast to this situation, however, none of the reagents tested gave a completely stable coloured solution when reacted with aqueous porphobilinogen solutions. A test was devised, however, using the BDMAB reagent in acid solution which gave a colour, stable for up to 40 minutes, when reacted with test porphobilinogen solutions.

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by Jian-hui Liu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (p. 112-118). / 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.

Thesis (Ph. D.)--University of Hong Kong, 1989.

Thesis (M. Phil.)--University of Hong Kong, 1991.