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I Asymmetric Photochemistry Ii Exploratory And Mechanistic Studies On The Triplet Sensitized Vapor Phase Photochemistry Of Allenes Iii Developments In The Synthesis Of Strained Cyclic Cumulenes, William Calvin Shakespeare

Doctoral Dissertations

The development and implementation of a new chiral triplet sensitizer derived from 1,1$\sp\prime$-binaphthol is described. Irradiation of 1,3-diphenylallene (16) in the presence of 4,5,6,7-tetrahydro-dinaphtho(2,1-g:1$\sp\prime,2\sp\prime$-i) (1,6) dioxecine (10) resulted in 0.66% optical induction. Irradiation of 1,3-cyclooctadiene (17) in the presence of 10 resulted in 11.3% optical induction. The singlet state of 10 could be effectively quenched by higher diene concentration, substantially reducing the optical yield. Irradiation of trans-1,2-diphenyl-cyclopropane (1) in the presence of 10 resulted in very low optical yields.

The mechanism by which triplet excited state allenes react in the vapor phase is investigated through both theory and experiment. Benzene …

Coordination Chemistry Of Polyphosphoxane Rings, Xiaoyong Sun

Doctoral Dissertations

Substitution of triphosphoxane rings on metal complexes containing labile ligands, M(CO)$\sb4$NBD and $\rm MX\sb2L\sb2$ (X = Cl, Br, I; L = DME, THF, NBD) and thermal reactions of bis(dialkylamino)phosphine oxides with metal hexacarbonyls yielded the tri-, tetra-, and pentaphosphoxane ring complexes cis-$\rm M(CO)\sb4\lbrack R\sb2NPO\rbrack\sb3,$ cis-$\rm M(CO)\sb4\lbrack R\sb2NPO\rbrack\sb4,$ cis-$\rm M\sb2(CO)\sb8\lbrack R\sb2NPO\rbrack\sb4,$ cis-$\rm M\sb2(CO)\sb7\lbrack R\sb2NPO\rbrack\sb5,$ cis-$\rm MX\sb2\lbrack R\sb2NPO\rbrack\sb4,$ and cis-$\rm MX\sb2\lbrack R\sb2NPO\rbrack\sb5$ as the isolated products. The P$\sb4$O$\sb4$ rings in metal tetraphosphoxane complexes appear in six coordination modes including the 1,3-chelating, 1,5-chelating boat-boat, boat-chair conformation, 1,3,5,7-chelating boat-boat cage mode, twist-boat mode, and 1,3,5-tridentate mode bridging two metals. A novel Ni(O)-cage complex $\rm …

Effects Of Soil Moisture, Soil Carbonate And Organic Matter Content On Vapor Phase Sorption Of Volatile Organic Compounds Using Inverse Gas Chromatography, John Stephen Schmeltzer

UNLV Retrospective Theses & Dissertations

Sorption of VOCs from the vapor phase to soils is an important variable in predicting VOC contaminant movement in unsaturated soils. Experiments were performed which evaluated the effects of soil moisture, carbonate, and organic matter content on VOC sorption. Sorption measurements were performed for ten VOC compounds: trichloroethylene (TCE); 1,1,1-trichloroethane (TCA); benzene; toluene; ethylbenzene; chlorobenzene; heptane; and pentane. Inverse Gas Chromatography (IGC) was the primary method used to measure VOC sorption in these experiments. Sorption for all the evaluated VOCs decreased with increasing moisture. Non-reversibility in the water characteristic curve of water had significant implications for the sorption of VOCs …

Groundwater Contamination By Selenium, Nitrate, Coliform Bacteria, And Volatile Organic Compounds In The Las Vegas Valley, Nevada, Shallow Aquifer Zone, Arthur Neil Bashor

UNLV Retrospective Theses & Dissertations

A network of 27 shallow groundwater monitoring wells in the Las Vegas Valley, Nevada, was sampled for selenium, nitrate, coliform bacteria and 37 volatile organic compounds. A distinct pattern of elevated levels of selenium, nitrates, and chloroform was observed in the developed portions of the valley. Evidence suggests that the probable sources for these contaminants are linked to the practice of high water-use irrigation for turfgrass landscaping. Selenium was observed to be concentrated in the upper 50 cm of an undisturbed soil sample, but can be mobilized by the application of irrigation water to the naturally seleniferous soils and transported …

Synthetic Applications Of The Photochemical Cycloaddition Reactions Of N-Acylindoles And Conformational Studies Of The Cycloadducts, Boke Zhang

Digitized Theses

The ability of a series of nitrogen-substituents to activate the cycloaddition photochemistry of indoles has been examined; the N-substituents were chosen in order to enable their removal following cycloaddition under mild neutral, acidic or basic conditions. N-substituted indoles, 17, 12 and 104c-g, were prepared in which the N-substituent is COPh, CO{dollar}\sb2{dollar}Et, CO{dollar}\sb2{dollar}CH{dollar}\sb2{dollar}CH{dollar}\sb2{dollar}SiMe{dollar}\sb3{dollar}, CO{dollar}\sb2{dollar}CH{dollar}\sb2{dollar}CH{dollar}\sb2{dollar}CN, CO{dollar}\sb2{dollar}Bu{dollar}\sp{lcub}\rm t{rcub}{dollar}, CO{dollar}\sb2{dollar}Ph, and CO{dollar}\sb2{dollar}CH{dollar}\sb2{dollar}Ph, respectively.;The silylethoxycarbonyl group of photoadducts derived from 104c can be removed by treatment of the adduct with fluoride ion in dichloromethane, the tert-butyloxycarbonyl group of adducts derived from 104e by treatment with trifluoroacetic acid at room temperature; the benzyloxycarbonyl group of adducts …

Radiotracers For The Angiotensin System, Vincenzo Quiquero

Digitized Theses

Angiotensin converting enzyme (ACE), a dipeptidyl carboxypeptidase, is one of the enzyme components of the renin-angiotensin-aldosterone system. ACE is responsible for the production of angiotensin II, a potent vasoconstrictor, and for the inactivation of the potent vasodepressor peptide bradykinin. The enzyme is a vascular endothelial component of many tissues (i.e. lungs, kidney, preoptic region of brain) and has been shown to be localized on the lumenal surface of the vascular endothelium. Diseases involving granuloma (i.e. sarcoidosis, silicosis, asbestosis) are known to change the distribution of ACE and to cause hypertension. A radiolabelled pharmaceutical which binds with ACE could permit the …

Investigations Of Ultrafast Dynamics Of Photoexcited Hemeproteins And Iodomethane In Condensed Phase Using Transient Raman And Absorption Spectroscopies., Huiping Zhu

LSU Historical Dissertations and Theses

This dissertation describes the development and application of transient Raman and absorption spectroscopies using 8 ps laser pulses for the study of photoexcitation dynamics of hemeproteins and CH$\sb3$I in the condensed phase. Transient Raman spectroscopy is a powerful ultrafast technique. Hemeproteins have been studied using this technique. The dynamics of vibrational cooling, geminate recombination, and structural change upon the photoexcitation of hemeproteins have been unambiguously separated. The vibrationally hot deoxyhemoglobin, oxyhemoglobin and photoproduct deoxy-liked hemoglobin have been directly detected. The deconvolved time constant of vibrational cooling for the species is about 2-5 ps. Direct evidence for the lack of geminate …

2,2',6,6'-Tetrasubstituted Diarylethynes: Models To Test Proximity And Position In Catalysis., Kevin Levon Evans

LSU Historical Dissertations and Theses

Enzymes exhibit extraordinary efficiency and specificity in catalysis. A source of the catalytic power observed in enzymes has been attributed to the ability of the enzyme-substrate complex to bring the substrate into close proximity to the catalytic groups with proper orientation for reaction. However, the contributions of proximity and of orientation to the origin of catalytic power have not been quantified. A series of tethered and untethered 2,2$\sp\prime,$6,6$\sp\prime$-tetrasubstituted diarylethynes have been proposed to study the effect of proximity of the catalytic group to the substrate on catalysis. The syntheses of the diarylethyne models require efficient procedures for the synthesis of …

Syntheses, Structures, And Characterizations Of 2,2',7,7'-Tetrasubstituted 1,1'-Ethynylenedinaphthalenes., Philippe Prince

LSU Historical Dissertations and Theses

In order to study intramolecular enzyme catalysis, chemical models have been designed to quantify the proximity and orientation effects which occur in carboxylate catalyzed hydrolyses. As part of this broader study, various 2,2$\sp\prime$,7,7$\sp\prime$-tetrasubstituted 1,1$\sp\prime$-ethynylenedinaphthalenes are synthesized from 2,7-dihydroxynaphthalene. Two different strategies are used to obtain the title compounds. The first strategy involves palladium-mediated couplings between electron-poor aryl iodides and electron-rich arylethynes and allows synthesis of unsymmetrical binaphthylethynes. The second approach couples two 2,7-disubstituted naphthalenes with tetrachlorocyclopropene in the presence of aluminum chloride, but only symmetrical binaphthylethynes are obtained. During the course of this work, a number of 1,2,7-trisubstituted naphthalenes, some …

Ph Optimization Of Nucleophilic Reactions And Mechanisms Of Reactions Of Sulfonyl Chlorides, Joe Ying Lam

Digitized Theses

This thesis consists of four chapters all involving the chemistry of sulfonyl chlorides in water.;Chapter 1 describes the mechanisms of the reactions of alkanesulfonyl chlorides with water with and without added nucleophiles. Evidence is provided that the hydrolysis of alkanesulfonyl chlorides proceeds (a) at low pH, by S{dollar}\sb{lcub}\rm N{rcub}{dollar}2-S attack of water, (b) at intermediate pH, by rate determining attack of hydroxide anion to form sulfene which is then trapped by water, and (c) at high pH, by way of sulfene both formed and trapped by hydroxide anion. Among the following pathways observed in the reaction of alkanesulfonyl chlorides with …

Nucleophilic Reactions Of Sulfonyl And Carbonyl Compounds, Darryl Frederick Klassen

Digitized Theses

This thesis contains topics in organic sulfur chemistry and general physical organic chemistry. In the first chapter a pH rate profile (log {dollar}k\sb{lcub}\rm obs{rcub}{dollar} vs pH) was determined for the hydrolysis of ethylene sulfone (1) over the pH range from 4 to 11.5 at 75{dollar}\sp\circ{dollar}C. The rate constant {dollar}k\sb{lcub}\rm obs{rcub}{dollar} was found to be of the form {dollar}k\sb{lcub}\rm obs{rcub}{dollar} = {dollar}k\sb{lcub}\rm w{rcub}{dollar} + {dollar}k\sb{lcub}\rm OH{rcub}{dollar} (OH{dollar}\sp-{dollar}) where {dollar}k\sb{lcub}\rm w{rcub}{dollar} = (8.71 {dollar}\pm{dollar} 1.38) {dollar}\times{dollar} 10{dollar}\sp{lcub}-5{rcub}{dollar} s{dollar}\sp{lcub}-1{rcub}{dollar} and {dollar}k\sb{lcub}\rm OH{rcub}{dollar} = (2.98 {dollar}\pm{dollar} 0.89) {dollar}\times{dollar} 10{dollar}\sp{lcub}-2{rcub}{dollar} M{dollar}\sp{lcub}-1{rcub}{dollar}s{dollar}\sp{lcub}-1{rcub}{dollar}. In the pH region that corresponds to the uncatalyed hydrolysis ({dollar}k\sb{lcub}\rm w{rcub}{dollar}, pH 4 …

In Search Of An Alternative Route To Germasilenes: The Synthesis And Chemistry Of (Halosilyl)Germanes, Umesh Ramji Parshotam

Digitized Theses

This thesis describes attempts to prepare a germasilene, a compound containing a germanium-silicon double bond, by either a {dollar}\beta{dollar}-elimination reaction or a reductive elimination reaction.;The precursor, Mes{dollar}\sb2{dollar}HGeSiClMes{dollar}\sb2{dollar}, 1, (Mes = 2,4,6-trimethylphenyl) was prepared by the addition of Mes{dollar}\sb2{dollar}HGeLi to Mes{dollar}\sb2{dollar}SiCl{dollar}\sb2{dollar} in THF in excellent yield. We examined the effect of changing the nature of the solvent, leaving group, base and ligands on the reaction between 1 and base.;Mes{dollar}\sb2{dollar}ClGeSiClMes{dollar}\sb2,{dollar} 29, and Mes{dollar}\sb2{dollar}BrGeSiClMes{dollar}\sb2{dollar}, 30, prepared by the chlorination and bromination of 1 respectively, were treated with lithium naphthalenide (LiNp) in an attempt to prepare Mes{dollar}\sb2{dollar}Ge = SiMes{dollar}\sb2{dollar} by a reductive elimination reaction. …