Date of Graduation

2000

Document Type

Dissertation/Thesis

Abstract

Part 1. Structure, stability, and mechanisms of oxidation and hydrolysis of a number of thiourea-S-oxides (thiourea dioxide; N-methylthiourea dioxide; N,N′-dimethylthiourea dioxide; thiourea and N,N′-dimethylthiourea trioxides; and sodium hydroxymethanesulfinate) have been investigated by means of UV-VIS, stopped-flow; X-ray crystallography; molecular calculations; ESR; NMR; and oxygen consumption studies. It was found that oxidation of thioureas does not always proceed through the generally accepted successive addition of oxygen atom to the sulfur center. Instead, thiourea dioxides appear to be the major end product in these oxidations. Mechanism of hydrolysis of thiourea dioxides in basic media reveals complex chemical kinetics which involves initial heterolytic cleavage of the C-S bond with the release of a powerful reducing species—sulfoxylate ion, SO 22−. Under aerobic conditions sulfoxylate ion is rapidly oxidized by the dissolved oxygen to yield sulfoxide radical ion, sulfite radical, and a series of reactive oxygen species among other products of decomposition. The mechanism was confirmed by numerical simulations of the reaction dynamics. Part 2. The oxidation of a number of pinacols and related ethers by ferriin has been examined by means of GC-MS, UV-VIS, stopped-flow, deuterium isotope and special salt effects, cyclic voltammetry, and NMR. Analysis of structural parameters indicates that both steric considerations and the presence of both hydroxyl groups are important for the oxidation reaction to take place. Steric considerations indicate that the reaction proceeds most rapidly when the hydroxyl groups are aligned in a syn orientation to each other. When both hydroxyl groups are present, the reaction proceeds more rapidly than when single hydroxyl group is present. When neither hydroxyl group is present in the molecule, no oxidation reaction takes place.

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