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Articles 121 - 138 of 138

Full-Text Articles in Physical Chemistry

A Sodium Salt Of The Dimer Of Boronoterephthalic Acid Anhydride, Scott Simmons, Albert Fratini, Vladimir Benin Apr 2011

A Sodium Salt Of The Dimer Of Boronoterephthalic Acid Anhydride, Scott Simmons, Albert Fratini, Vladimir Benin

Chemistry Faculty Publications

The title compound, sodium bis­(6-carb­oxy-1-hy­droxy-3-oxo-1,3-dihydro-2,1-benzoxaborol-1-yl)oxidanium, Na+·C16H15B2O13-, was prepared in two steps from 2-bromo-p-xylene. Its crystal structure was determined at 140 K and has triclinic (P) symmetry. The compound presents a unique structural motif, including two units of the cyclic anhydride of boronoterephthalic acid, joined by a protonated, and thereby trivalent, oxonium center. Association in the crystal is realized by complementary hydrogen bonding of the carboxyl groups, as well as by coordination of the sodium cations to the oxygen centers on the five-membered rings.

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Theoretical Investigation Of A Reported Antibiotic From The 'Miracle Tree' Moringa Oleifera, Michael Horwath, Vladimir Benin Apr 2011

Theoretical Investigation Of A Reported Antibiotic From The 'Miracle Tree' Moringa Oleifera, Michael Horwath, Vladimir Benin

Chemistry Faculty Publications

Moringa oleifera, sometimes called the “Miracle Tree,” has received international attention for its potential to improve health in impoverished tropical areas. In addition to high vitamin content in the leaves and pods, the tree contains compounds with antioxidant and antibacterial properties. This study focused on the theoretical investigation of the suggested structure of one antibacterial compound, “pterygospermin,” whose existence was proposed after some studies of the roots of M. oleifera. The structure of pterygospermin was first proposed by a research group working in the 1950s, but later studies have not found evidence of this compound and have instead …

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The Impact Of Driving Conditions On Phev Battery Performance, Nathan Christensen, John Patten, Steven Srivastava, Gary P. Nola Jan 2011

The Impact Of Driving Conditions On Phev Battery Performance, Nathan Christensen, John Patten, Steven Srivastava, Gary P. Nola

Green Manufacturing Research Journal

The battery performance of a modified Prius with a 5 kWh plug-in battery was documented for a year to determine the impact of environmental conditions and user attributes on vehicle performance.  Both fuel economy and pure electrical efficiency were compared to ambient temperature.  The fuel economy has a positive relationship with ambient temperature until approximately 70˚F where the efficiency begins to drop.  Electrical performance has a positive linear relationship with ambient temperature.  With the emergence of electric vehicles (EVs) and PHEVs from a variety of automotive manufacturers, information on EV and PHEV performance for consumers will become more important.

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Synthesis And Catalytic Activity Of Nanostructured Cerium Oxide, Neil J. Lawrence Dec 2010

Synthesis And Catalytic Activity Of Nanostructured Cerium Oxide, Neil J. Lawrence

Department of Chemistry: Dissertations, Theses, and Student Research

Cerium oxide (ceria, CeO2-x where x is 0 to 0.5) has been one of the most widely used heterogeneous catalysts particularly in three way catalytic converters. Most of the catalytic traits can be attributed to two properties of ceria: first, the high mobility and storage capacity of oxygen within the lattice; second, the ease with which cerium changes between Ce3+ and Ce4+ states. These properties, combined with the abundance of cerium on earth, make ceria a low-cost highly effective alternative to noble metal catalysts. Recent research has been focused on the nanoscale properties of ceria.

The effect …

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Preparation And Characterization Of Some Substituted Benzyl N-Nitrosocarbamates Containing An N-2-(Methylthio)Ethyl Or A Bis(2-Aminoethyl)Sulfide Functionality, Satya Venkata, Eric Shamo, Vladimir Benin Jan 2009

Preparation And Characterization Of Some Substituted Benzyl N-Nitrosocarbamates Containing An N-2-(Methylthio)Ethyl Or A Bis(2-Aminoethyl)Sulfide Functionality, Satya Venkata, Eric Shamo, Vladimir Benin

Chemistry Faculty Publications

The synthesis and characterization of some substituted benzyl N-nitrosocarbamates with an N-2-(methylthio)ethyl or a bis(2-aminoethyl)sulfide functionality is reported, as a part of a long-term goal to design and prepare novel photolabile structures that could be used as substances for controlled release of alkylating and/or crosslinking agents. The synthesis was accomplished by reaction of benzyl chloroformates with the corresponding amines, resulting in the preparation of carbamates. The latter were subsequently nitrosated, utilizing two different N-nitrosation methods, to yield the target structures.

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Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis May 2008

Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis

Chemistry Faculty Publications

Chlorination and bromination reactions of thiazolo[5,4-d]thiazole led to the generation of its mono- and dihalogenated derivatives. These are the first instances of successful direct electrophilic aromatic substitution in the thiazolo[5,4-d]thiazole ring system. X-ray analysis demonstrates that both 2-bromothiazolo[5,4-d]-thiazole and 2,5-dibromothiazolo[5,4-d]thiazole are planar structures, with strongly manifested π-stacking in the solid state. Theoretical analysis of the pyridine-catalyzed halogenation (MP2/6-31+G(d) and B3LYP/6-31+G(d)calculations) reveals that introduction of one halogen actually leads to a slightly enhanced reactivity towards further halogenation. Several halogenation mechanisms have been investigated: 1) The direct C-halogenation with N-halopyridine as electrophile; …

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C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin Feb 2008

C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin

Chemistry Faculty Publications

The current report presents the first theoretical study of the restricted CN bond rotation in carbamoyl chlorides. Several N-benzyl-N-methylcarbamoyl chlorides were investigated, with varying pattern of substitution in the aromatic ring. Optimizations and frequency calculations were conducted employing DFT at the B3LYP/6-31+G(d) level of theory. Each of the studied structures exhibits a pair of rotamers (s-Z and s-E), generated upon rotation around the C(O)N bond. The s-E isomer is the global minimum in every case, but the preference for it is usually less than 1 kcal/mol. Two possible transition state structures were identified …

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An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan Jan 2007

An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan

Articles

Work in photochemistry work peaked in the 1980’s where there was the prospect of using sunlight shining on suspensions of titanium dioxide in order to catalytically cleave water into hydrogen and oxygen [1-5]. In this way a clean and efficient method of producing hydrogen as a fuel was envisaged. However, there was a requirement to use a rather high energy light to achieve the splitting and it was not as efficient with visible light[5]. Doped TiO2 layers have been used in a three electrode system for formic acid degradation[6]. In this work, the system uses an electrode coated with TiO2 …

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Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond Jan 2007

Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond

Articles

Urea–calix[4]arenes 1 and 2 were synthesised and incorporated into ISE membranes for assessment as sensors for inorganic anions in water. 1 revealed a strong response to all anions following the Hofmeister selectivity order. For ISEs of 2, the response to a portion of the anion series was suppressed, increasing the margin of selectivity of nitrate over chloride, a common interferant of nitrate in fresh and marine water samples. The performance of ISEs containing 2 was compared to commercially available alkylammonium nitrate ion-exchange salts used for nitrate sensing. Our ISEs performed favourably in terms of sensitivity, linear range and LOD performing …

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A Novel Tio2 / Pvc Layer For Use In A Photoelectrochemical Cell, Faiza Touati, John Cassidy, Kevin Mcguigan Jan 2007

A Novel Tio2 / Pvc Layer For Use In A Photoelectrochemical Cell, Faiza Touati, John Cassidy, Kevin Mcguigan

Articles

A novel method of coating titanium dioxide on a glassy carbon electrode as a polyvinylchloride composite , is described. On illumination , there is an enhanced voltammetric current at this TiO2/PVC composite in aqueous formic acid solution. This electrode is used as the basis of a formic acid fuel cell where oxygen is reduced at a platinum cathode. The system yields 100 cm-2 for 0.01 mol dm-3 HCOOH in 0.1 mol dm-3 NaOH under illumination from a 150 W xenon lamp. The current without illumination is 0.5 cm-2.

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Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin May 2006

Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin

Chemistry Faculty Publications

The current article reports theoretical studies (DFT: B3LYP/6-31+G(d)) on the structure and alkylation reactions of the anions of some secondary N-nitrosocarbamates, a class of ambident nucleophiles whose chemistry has been little explored. Several anions (1–4), with an increasing size of the carbamate alkyl (aryl) group were investigated, in an attempt to establish the influence of the size of that group on the thermal stability and regioselectivity of alkylation of the title anions. The conclusion is that thermal stability and the mode of reaction are affected significantly only in the presence of very large and branched carbamate groups. The thermal …

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Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond Jan 2006

Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond

Articles

The current work is amongst the first to examine the potential usefulness of the nitrile functional group in potentiometric analytical sensors for soft metals. Nitrile functionality has hereby been incorporated into a calix[4]arene skeleton to give a series of new cation selective hosts. The analytical sensing behaviour of these hosts was examined by Ion Selective Electrode (ISE) based potentiometry. In all cases a preference for soft metals was observed, explained primarily in terms of soft–soft compatibility between calix[4]arene nitrile hosts and metal guests in combination with a classical ‘lock and key’ best fit mechanism. Hosts 2, 3 and 4 showed …

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Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin Jan 2006

Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin

Chemistry Faculty Publications

We report in detail the preparation of two substituted terephthalic acids: 2‐sulfomethylterephthalic acid (1) and 2‐phosphonoterephthalic acid (2). Efficient, short syntheses have been developed for both compounds. They are potentially useful monomers for construction of acid‐pendant polymer chains.

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Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin Jan 2006

Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin

Chemistry Faculty Publications

We are presenting the preparation, characterization and density functional theory (DFT) studies {B3LYP/6-31+G(d)) of several reiated classes of N-nitrosocarbamates and N-nitrosoureas. The iong-range goal is the design and preparation of compounds, which would undergo photochemical or hydrolytic decomposition, to yield stabilized cyclic cations that can serve as alkylating agents at various nucleophilic centers, including DNA bases.

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Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin May 2005

Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin

Chemistry Faculty Publications

The present report describes the preparation and characterization of several N-2-(trimethylsilyl)ethyl-N-nitrosocarbamates, designed as precursors to thermally unstable secondary N-nitrosocarbamate anions via fluoride-assisted cleavage. X-ray structural studies demonstrate that the core N-nitrosocarbamate moiety has a nearly planar geometry, with an s-E orientation at the N–N bond. DFT calculations (B3LYP/6-31+G(d)) reproduce accurately the structural features of the title compounds and detailed conformational analysis at the same level of theory addresses the long-standing issue of preferred geometries for three classes of related structures: N-nitrosocarbamates, N-nitrosoureas and N-nitrosoamides. Desilylation studies demonstrate that both the …

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Reactions Of Aqueous Chlorine With Valine In Model Solutions And In Wastewater, Erika Forrer Mccormick Oct 1991

Reactions Of Aqueous Chlorine With Valine In Model Solutions And In Wastewater, Erika Forrer Mccormick

Chemistry & Biochemistry Theses & Dissertations

Solutions of the amino acid valine were chlorinated to seven chlorine-to-nitrogen mole (Cl/N) ratios and analyzed by high performance liquid chromatography, gas chromatography/mass spectroscopy, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The chlorination products found were N-chlorovaline, isobutyraldehyde, isobutyronitrile, and N-chloroisobutyraldimine. Their product distribution depends on the level of chlorination and pH. The main products identified at the lower CI/N mole ratios were N-chlorovaline and isobutyraldehyde, whereas at the higher CI/N mole ratios isobutyronitrile and N-chloroisobutyraldimine were identified as the main products. The concentration and the chlorination products of valine in municipal wastewater were also determined. The chlorination products of …

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Isolation And Characterization Of Frullanolide From Frullania Franciscana (Howe), Marshall Stuart Sass Mar 1981

Isolation And Characterization Of Frullanolide From Frullania Franciscana (Howe), Marshall Stuart Sass

Dissertations and Theses

Investigation of the ether extract of the liverwort Frullania franciscana (Howe) resulted in the isolation of the sesquiterpene lactone frullanolide. The separation techniques of thin-layer chromatography, dry column chromatography, and liquid column chromatography were evaluated. Only liquid column chromatography was found useful. Fractions from alumina liquid column separations had infrared spectra which resembled the published spectrum of frullanolide. The identity of the compound obtained from F. franciscana (Howe) was established after extensive purification by comparison of its infrared and nuclear magnetic resonance spectra with published spectra of frullanolide.

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Water Chemistry Survey Of Boulder Basin, Lake Mead, P. R. Tramutt, Bureau Of Reclamation Jun 1965

Water Chemistry Survey Of Boulder Basin, Lake Mead, P. R. Tramutt, Bureau Of Reclamation

Publications (WR)

The survey results indicate that the impoundment of water behind Hoover Dam has not adversely affected the dissolved oxygen (DO) content and that water quality and DO content were uniform regardless of depth. The study made in April-May 1964 will provide water quality data of Lake Mead prior to releases from Lake Powell as a basis for evaluating Lake Powell's effect on water quality and limnology of Lake Mead. The performance of a DO analyzer was tested and found unsatisfactory at depths below 150 ft. Parameters tested by standard chemical analyses of water samples in the Denver Laboratory and by …

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