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Full-Text Articles in Physical Sciences and Mathematics
Toward Hydrogen Bonds Of Predictable Geometry, Robert Shao-Chih Hsu
Toward Hydrogen Bonds Of Predictable Geometry, Robert Shao-Chih Hsu
Theses and Dissertations
A literature review on the geometry of hydrogen bonding showed that the geometry is often de-emphasized or even ignored, probably because of the inherent flexibility of many systems studied. Examination of molecular models suggested the geometrically constrained bicyclo [2, 2, 1] heptane system wherein hydrogen bond distances and angles might be more easily predicted. Dihydroboration-oxidation of norbornadiene was shown to yield exo, exo-2,5-norbornadiol, thus clarifying uncertainties in the literature. 2, 5-Norbornadiol was oxidized to the corresponding dione, heretofore inadequately characterized. Several derivatives of the dione were prepared, and spectral data were accumulated for the dione, its precursor, and its derivatives. …
Synthesis And Metal Coordination Properties Of Some Cyclic Polyethers And Polythioethers, Barry Lant Haymore
Synthesis And Metal Coordination Properties Of Some Cyclic Polyethers And Polythioethers, Barry Lant Haymore
Theses and Dissertations
Thermodynamic values for cation-cyclic polyether interactions for several systems are reported and discussed in light of ligand geometry, cation selectivity, solvent effects, structure, stoichiometry and the nature of the coordinate bond. Cyclic polyethers are shown to be remarkably good ligands even in water and to have marked selectivity for d0, d10 and d10 s2 cations. Syntheses of one new cyclic polyether and several new mixed cyclic polyether-thioethers are reported. Cyclic chelates with smaller rings are shown to prefer smaller cations, but this selectivity is masked by the hydration energy of the cation. Except for thiophillic cations such as Hg2+ and …
A New Method For The Preparation Of Alkylnaphthyl Ethers And Sulfides, Edward Ying-Shih Chen
A New Method For The Preparation Of Alkylnaphthyl Ethers And Sulfides, Edward Ying-Shih Chen
Theses and Dissertations
The reaction of monohalonaphthalenes with metal alkoxides and mercaptides in a solvent mixture of the corresponding alcohol and dimethyl sulfoxide (DMSO) has been studied. These reactions are convenient methods for the preparation of alkylnaphthyl ethers and sulfides. Only direct nucleophilic substitution was observed in the reactions of bromonaphthalenes with sodium methoxide and sodium nbutyl mercaptide. The reaction of fluoronaphthalene with potassium t-butoxide also proceeded by way of direct nucleophilic substitution rather than the 1,2-dehydronaphthalene intermediate as in the reactions of bromonaphthalene with potassium t-butoxide. The use of a base which is weaker than t-butoxide can change the apparent reaction mechanism …
Rhenium Catalyzed Hydrogenation Of Maleic Anhydride And Crotonaldehyde, William Russel Dixon
Rhenium Catalyzed Hydrogenation Of Maleic Anhydride And Crotonaldehyde, William Russel Dixon
Theses and Dissertations
The preparation of a number of supported rhenium catalysts is reported. The determination of their activity and selectivity and of optimal reaction parameters for the reduction of maleic anhydride and crotonaldehyde is reported. Optimal time of hydrogenation was chosen as one hour and pressures were chosen as 2000 psig for crotonaldehyde and 3000 psig for maleic anhydride. Quantitative reduction of maleic anhydride to tetrahydrofuran occurred at 275° with charcoal supported rhenium catalysts. Lower temperatures (ca. 200°) produce quantitative amounts of butyrolactone. Unsupported catalysts at low temperatures (100°) selectively reduce crotonaldehyde to crotyl alcohol, but at very low conversion rates. Temperatures …
Electrolytic Synthesis Of [Gamma]-Diketones, Leon F. Pahler
Electrolytic Synthesis Of [Gamma]-Diketones, Leon F. Pahler
Theses and Dissertations
Four γ-diketones were synthesized by using a modification of the Kolbe electrolytic condensation of β-ketocarboxylic acids. [--see equation in thesis--] The following γ-diketones were synthesized in moderate yields: 2,5-hexanedione, 4,7-decanedione, 2,2,7,7-tetramethyl- 3,6-octanedione, and 1,4-diphenyl-1,4-butanedione (34, 39, 23, and 27, respectively). However, attempted preparation of the following γ-diketones failed: 3,4-dimethyl- 2,5-hexanedione, 3,3,4,4-tetramethyl-2,5-hexanedione, and 1,4-di(2-thienyl)-1,4-butanedione. Attempts to electrolytically condense α-alkyl and α, α-dialkyl substituted monocarboxylic acids have been reported and all attempts have ended in failure; similarly, the attempts to synthesize 3,4-dimethyl and 3,3,4,4-tetramethyl- 2,5-hexanedione from 2-methyl and 2,2-dimethyl-3- oxobutanoic acid, respectively, failed. The preparation of 1,4-di(2-thienyl)-l,4-butanedione failed because the product or …
Enzymatic Synthesis Of Oligoribonucleotides Of Defined Base Sequence, Mark J. Rowe
Enzymatic Synthesis Of Oligoribonucleotides Of Defined Base Sequence, Mark J. Rowe
Theses and Dissertations
The synthetic reaction of ribonuclease T_1 has been studied as to its potential for the synthesis of oligoribonucleotides of defined base sequence. Conditions have been determined for maximum synthesis with respect to percentage incorporation of both guanosine 2',3'-cyclic phosphate (donor), and cytidine (acceptor). With regard to maximum acceptor incorporation, a donor blocked at the 5'-hydroxyl has been used to drive the reaction. It has also been shown that acceptor incorporation decreases as the chain-length increases up to the hexanucleotide. Synthesis of a 3'-blocked substrate for polynucleotide phosphorylase for use in chain termination studies was attempted using adenylate kinase. In this …