Würzburg, Phil. Diss. v. 27. Jan. 1916, Ref. Buchner.

No description available.

The catalytic effects of several acids and metal salts on the cis-trans isomerization of azobenzene in aqueous ethanol were examined kinetically. The effect of perchloric acid is apparently due to H⁺ ions: a catalytic mechanism involving the formation of the conjugate acid of azobenzene has been postulated to interpret these results. To account for the much higher catalytic activity found for hydrochloric acid, an additional path, involving catalysis by undissociated HCl molecules has been proposed. Acetic acid was found to be inactive. Of the metal salts examined only those of Cu⁺⁺ shoved pronounced catalytic activity, which is interpreted in terms of a catalytic mechanism involving coordination of cupric ions with the azo group. Simultaneous coordination of Cu⁺⁺ and H⁺ has been proposed to account for the high catalytic activity of cupric salts in the presence of acids. / Science, Faculty of / Chemistry, Department of / Graduate

The mechanism of the carbonate catalyzed conversion of 2,4-dinitrophenyl 2 ,3 ,4,6-tetra-0-acetyl-β-D-glucopyranoside in DMSO to an equilibrated mixture of the α- and β-glycosides has been investigated using a variety of techniques. Pseudo-first-order rate constants (k) measured for the anomerization of the parent substrate and the 1-deuterio substrate indicated a secondary deuterium isotope effect of kH/kD = 1.09 ± 0.06. Pseudo-first-order rate constants measured for several deoxy and deoxyfluoro derivatives of the parent sugar showed that the deoxyfluoro sugars react at least as fast as the parent sugar whereas the deoxy sugars reacted more slowly. In addition to the 2,4-dinitro-phenyl glucoside, 2,6-dinitrophenyl glucoside also was found to anomerize, yet attempts to exchange the 2,4-dinitrophenolate groups of the glucoside with added 2,6-dinitrophenolate anion and vice versa were unsuccessful. Exchange of the proton at the anomeric carbon with a deuteron also does not occur when the anomerization is performed in the presence of a deuteron source (and vice versa). Exchange of the glucosyl residue was observed, however, when the 1-deuterio substrate was anomerized in the presence of non-deuterated 2,3,4,6-tetra-O-acetyl-D-glucopyranose. ¹H-n.m.r. of the 2,4-dinitrophenyl α-glucoside isolated from this reaction indicated that the a-glucoside possessed only 50% of the deuterium label, at the anomeric center. These results along with the observation of a Meisenheimer intermediate indicate that the anomerization proceeds via nucleophilic aromatic substitution and as such is novel mechanism for glycoside anomerization. / Science, Faculty of / Chemistry, Department of / Graduate

The blue and green forms of MoOCl₂(PMe₂Ph)₃ and [LWOCl₂]PF₆ (L = 1,4,7-trimethyltriazacyclononane) are not examples of distortional isomerism. For both systems, the blue form is pure and the green form is a mixture of the blue complex and other components. Characterizations of the green material of each indicates that green "MoOCl₂(PMe₂Ph)₃" is a mixture of MoOCl₂(PMe₂Ph)₃ and MoCl₃(PMe₂Ph)₃ and that green "[LWOCl₂]PF₆" is a mixture of [LWOCl₂]PF₆ and two other species; one is a W(IV) and the other a W(VI) compound. Both solid state (XPS, Raman, infrared, powder X-ray diffraction) and solution phase (¹H NMR, UV-visible, EPR, cyclic voltammetry) measurements were applied to the respective green materials, presenting a consistent description of their composite nature. A single crystal X-ray structure determination of a crystal of green "MoOCl₂(PMe₂Ph)₃" allowed the compositional disorder to be partially resolved in this case, due to the high composition of MoOCl₃(PMe₂Ph)₃ in the sample (ca. 0.30 mole percent by XPS and visible spectroscopies). The single crystal X-ray diffraction data from the original single crystal study of green "[LWOCl₂]PF₆" were reinvestigated to ascertain whether compositional disorder could also be implicated in this system. Several composite models were applied to these data, resulting in improved fits to the observed data. This indicated that the original data collected for the crystal of green "[LWOCl₂]PF₆" could not support distortional isomerism in green "[LWOCl₂]PF₆". X-ray structure calculations on models of the compositional disorder in both systems illustrated the pronounced effect of disordering chlorine electron density on the derived metal-oxo bond lengths. A calibration curve of Mo-Cl bond length versus composition calculated from these models resulted in a favorable comparison of this present theoretical work with other experimental X-ray studies of the MoOCl₂(PMe₂Ph)₃ system. Other examples of mixtures mistaken for pure materials are also discussed as well as a recent resurgence of distortional isomerism in certain niobium complexes. The nature of the compositional disorder characterized for the MoOCl₂ (PMe₂Ph)₃ and [LWOCl₂]PF₆ systems has profound implications for metal-ligand distances determined by X-ray crystallography.

No description available.

Thesis (Ph. D.)--Columbia University, 1942. / Vita. Bibliography: p. 15.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 122-124). Available also in a digital version from Dissertation Abstracts.