Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1954. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 136-138).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. / Keywords: thiadiazoles; electrocyclic; 3-sigmatropic. Includes bibliographical references (p.622-623).

Photochemical reactivity of several dibenzannelated systems has been investigated to demonstrate that the driving force inherent in many of their reactions is the attainment of a 4n π-electron system or intermediate in S1. It has been shown that the inherent driving force for the benzylic C-H bond ionization in 9H-xanthene (125) and 9H-thioxanthene (136) is the formation of 8π-electron cyclically conjugated carbanion intermediates 130 and 137, respectively, in S1. Formation of deuterium incorporated products when 125 and 136 are photolyzed in NaOD-EtOD solutions and protium incorporation in products when photolysis of 123 and 134 is carried out in NaOH-EtOH is consistent with the intermediacy of carbanions in these reactions. Fluorescence quenching of 123 and 125 by ethanolamine in CH3CN gave linear Stern-Volmer plots, with kq = (2.16 ± 0.05) x [special characters omitted] for 125 and (1.12 ± 0.05) x [special characters omitted] for 123, which corresponds to an isotope effect for quenching by ethanolamine, of [special characters omitted] = 1.92 ± 0.04. Enhanced stability of 8π carbanions in S1 is further evidenced in the photodecarboxylation of xanthene-9-carboxylic acids (142 and 145) and thioxanthene-9-carboxylic acids (147 and 148) in aqueous solution. The intermediacy of carbanions has been demonstrated in the product studies carried out in 80% [special characters omitted] solution. A mechanism has been proposed which involves heterolytic bond cleavage of the carboxylate ion in S1 to give intermediate carbanions. Additional support for the excited state stability of 4n systems comes from the studies of 155. Photoexcitation of bent 155 results in its planarization to give planar 155 in S1. The driving force for this change of conformation of 155 is believed to be the attainment of a conjugated 8π-electron internal cyclic array in S1. Photolysis of substituted suberenes in aqueous [special characters omitted] results in benzylic C-H bond cleavage in these systems in S1 the efficiency of which is greatly affected by the nature of substituent present. Results obtained in this study are consistent with benzylic C-H bond cleavage, with H2C acting as the base, to give intermediate carbanions in S1. Quantum yields of exchange in [special characters omitted] (L = H or D) and in a variety of other solvent mixtures have been measured. The photochemistry of xanthenium (99 and 114) and thioxanthenium (219) cations has been studied in aqueous [special characters omitted] in the presence of di- and trimethoxybenzenes. It has been shown that the primary photochemical step is electron transfer from methoxybenzenes to singlet excited 99 and 114. The radical intermediates thus generated subsequently react with 02 to give peroxy compounds as final products. These and other results of the photochemistry of dibenzannelated systems show that there is much interesting photochemistry to be discovered in these molecules. / Graduate

The photochemical generation of several novel quinone methide-type intermediates has been observed upon photolysis of pyridoxine (150-Vitamin B₆) and its derivatives 151 and 152, hydroxybiphenyl alkenes 153 and 154, and hydroxybiphenyl alcohols 159 and 160. Mechanistic investigations, utilizing product, fluorescence and laser flash photolysis studies, have suggested two distinct pathways for the formation of these reactive intermediates, depending upon the functional groups present on the progenitor. Formal excited state intramolecular proton transfer (ESIPT) between the phenol and the alkene led to quinone methides upon irradiation of the hydroxybiphenyl alkenes, while excited state proton transfer (ESPT) to solvent followed by dehydroxylation was responsible for formation of these intermediates from the hydroxybiphenyl alcohols. The quinone methide-type intermediates obtained from the pyridoxine systems arise from formal loss of water, although it is not certain whether this is through ESIPT or ESPT from the phenol at neutral pH. Studies of the photogeneration of quinone methide-type intermediates from the pyridoxine systems are important due to their biological relevance. Formation of such reactive intermediates in vivo may explain some of the toxicological properties associated with the intake of large doses of the vitamin. Irradiation of 150 or 151 in 1:1 CH₃OH/H₂O gave the corresponding methyl ethers (Φp = 0.18 and 0.21, respectively), consistent with formation of quinone methide-type intermediates. Similarly, photolysis in aqueous CH₃CN with ethyl vinyl ether resulted in the regioselective formation of the respective chroman products through [4+2] cycloaddition. LFP spectra pointed to formation of two quinone methide-type intermediates upon irradiation of both 151 and 152 in neutral aqueous solution, only one of which is present at pH 12. Previous studies on m-hydroxystyrene have suggested that m-quinone methide formation occurs via formal ESIPT between the phenol and the alkene, mediated by a bridging water trimer. Studies on 153 and 154 were undertaken to determine whether this solvent-mediated ESIPT can occur over longer distances. The photochemistry of the related hydroxybiphenyl alcohols (159 and 160) was also investigated, as quinone methides have been observed upon photolysis of similar systems. Irradiation of 153 and 154 in 1:1 CH₃CN/H₂O gave photohydration products (Φp = 0.013 and 0.1, respectively) via attack of water on the respective quinone methides. pH studies implicated formal ESEPT in formation of these reactive intermediates. Photolysis of the analogous methyl ethers of the phenols suggested the intermediacy of carbocations in the observed photohydration reaction, as quinone methides cannot be generated in these systems. Hydroxybiphenyl alcohols 159 and 160 yielded the corresponding photomethanolysis products (Φp = 0.04 and 0.22) in aqueous methanol, through attack of CH₃OH on the respective quinone methides. In this case, pH studies indicated that quinone methide formation occurs via ESPT and dehydroxylation. Significant quenching of fluorescence firom the hydroxybiphenyl alkenes with small amounts of added water implied that H₂O is directly involved in reaction from the singlet excited state. Loss of fluorescence firom 154 was found to depend on [H₂O ]³, however, the distance required for ESIPT in these systems is too large to be bridged by a water trimer. As such, the non-linear quenching has been attributed to deprotonation of the phenol by a cluster of one or two water molecules, with concerted protonation at the alkene by another molecule of water not associated with the cluster. Fluorescence quenching of the hydroxybiphenyl alcohols required much larger [H₂O], and implied a different mechanism of reaction, consistent with the proposal of ESPT and dehydroxylation. LFP studies indicated the assistance of water is required for formation of a long-lived transient (600 nm, t = 150 μs) upon irradiation of 153, however, it cannot be definitively assigned to the quinone methide. Although no evidence was found for quinone methide formation in LFP studies of 154 and 160 due to its suspected short lifetime, the respective carbocation (420 nm, t =8.5 μs) has been observed upon irradiation in 2,2,2-trifluoroethanol. / Graduate