Chemistry Commons^™

Condensation Of Supersaturated Vapors Of Hydrogen Bonding Molecules: Ethylene Glycol, Propylene Glycol, Trimethylene Glycol, And Glycerol, David B. Kane, M. Samy El-Shall

Chemistry Publications

The critical supersaturations required for the homogeneous nucleation (rate of 1 drop cm⁻³ s⁻¹) of ethylene glycol, propylene glycol, trimethylene glycol and glycerol vapors have been measured over wide temperature ranges (e.g., 280–400 K) using an upward thermal diffusion cloud chamber. At lower temperatures the experimental nucleation rates are much higher than the predictions of the classical nucleation theory. Glycerol shows the best agreement between experiment and theory in the temperature range of 340–370 K. An apparent increase in the critical supersaturation of glycerol is observed with increasing carrier gas (helium) pressure and this effect is more …

Oxidation States And Magnetism Of Fe Nanoparticles Prepared By A Laser Evaporation Technique, B. J. Jönsson, T. Turkki, V. Ström, M. S. El-Shall, K. V. Rao

Chemistry Publications

Nanoparticles of iron and iron oxide have been prepared in a thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about 60 Å. This is consistent with the mean particle size estimated from the magnetic data. The oxidation levels of these nanoparticles prepared at different partial oxygen pressures were investigated using FTIR. All the samples are found to exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. Magnetic anisotropy constants are calculated from the frequency dependence of the blocking temperatures are found to …

Interactions Among The Stationary Phase, The Mobile Phase, And The Solute In Liquid Chromatographic Systems, Zengbiao Li

Theses and Dissertations

Interactions among the stationary phase, the mobile phase, and the solute in liquid chromatography' have been studied. A strong dependence of the stationary phase properties on the mobile phase composition may arise from their interactions.

The solvatochromic comparison method, which can give estimates for the dipolarity-polarizability, the hydrogen-bonding acidity, and the hydrogen-bonding basicity of a solvent, represented by the solvatochromic parameters π⁺, α and β, respectively, was used to study the surface properties of silica in the presence of n-hexane-chloroform or n-hexane-ethyl ether mixtures. A high dipolarity- polarizability, a high hydrogen-bonding acidity, and a low hydrogen-bonding basicity …

Phosphorus Bearing Substrates In Ring Expansion Reactions, Bradley K. Norwood

Theses and Dissertations

A variety of substituted phosphonium salts, phosphorus ylides and phosphonates were studied to assess their utility in ring expansion reactions. The strategy involved formation of fused ring systems whose ring strain could be exploited to accomplish ring expansion to medium sized rings. β-Alkoxy vinylphosphonium salts were found to be unreactive with species such as the dimethylsulfoxonium methylide anion, Simmons-Smith type reagents. and carbenes in attempts to produce cyclopropyl phosphonium salts.

C-Alkylation of β-keto phosphorus ylides using haloalkanes bearing terminal groups that could be converted and reacted with the B-carbonyl, was also examined as a method for accessing strained rings bearing …

Gas Phase Clustering Of N2 Molecules On To Tio+: Comparison With Ti+ And Evidence For The Octahedral Structure Of Tio+(N2)5, George M. Daly, M. Samy El-Shall

Chemistry Publications

A striking difference in the clustering efficiency of Ti⁺ and TiO⁺ toward N₂ or O₂ has been observed in a laser vaporizationhigh pressure mass spectrometric source. Evidence for the magic number n=5 within the sequence TiO⁺(N₂) _n is presented. The results are consistent with an octahedral structure for TiO⁺(N₂)₅.

Ab Initio Equilibrium Constants For H2o–H2o And H2o–Co2, Nancy Renyou Zhang, Donald D. Shillady

Chemistry Publications

Ab initio 6‐31G** electronic structure calculations have been used to determine the minimum energy geometries and vibrational frequencies of molecular clusters of water and carbon dioxide. Application of statistical thermodynamics leads to theoretical equilibrium constants for gas phase dimerization of water and the formation of an adduct of carbon dioxide with water.The low energy vibrations of the clusters lead to much larger contributions to the vibrational partitioning of the energy than do the fundamental vibrations of the monomeric species. A new ‘‘Harmonic‐Morse’’ formula is derived to estimate anharmonicity from optimized harmonic frequencies and two additional values on the potential surface …

Monte Carlo Simulation Of Acetonitrile Clusters [Ch3cn] N , N=2–256: Melting Transitions And Even/Odd Character Of Small Clusters (N=2–9), Heat Capacities, Density Profiles, Fractal Dimension, Intracluster Dimerization, And Dipole Orientation, D. Wright, M. Samy El-Shall

Chemistry Publications

The thermodynamic and structural properties of acetonitrile clusters [CH₃CN] _N , N=2–15, 20, 30, 60, 128, and 256 have been investigated using Monte Carlo simulation. Interactions in the small clusters (N≤9) are dominated by antiparallel pairing of the molecular dipoles. The simulations reveal rigid ↔ fluid (melting) transitions with a remarkable even–odd alternation in the transition temperatures for the N=2–9 clusters. The higher melting temperatures of the even‐N clusters arise as consequences of the antiparallel paired dipoles which provide favorable electrostatic interactions. Even–odd alternation has also been observed in the configurational energies and …

Homogeneous Nucleation In Supersaturated Vapors Of Polar Molecules: Acetonitrile, Benzonitrile, Nitromethane, And Nitrobenzene, D. Wright, R. Caldwell, C. Moxely, M. S. El-Shall

Chemistry Publications

The critical supersaturations (S _c ) required for the homogeneous nucleation of acetonitrile, benzonitrile, nitromethane, and nitrobenzene vapors have been measured over wide temperature ranges using a thermal diffusion cloud chamber. At T _r =0.44, the experimental results are higher than the predictions of the classical nucleation theory by 20% (CH₃NO₂), 50% (CH₃CN), 57% (C₆H₅NO₂), and 112% (C₆H₅CN). This trend correlates well with the dipole moments and to a lesser extent with the polarizabilities of these substances. Corresponding states of simple fluids and …

Analysis Of Homogeneous Nucleation Data Of Polar Molecules: Vapor Association, Dipole Orientation, And Elongated Clusters, D. Wright, M. S. El-Shall

Chemistry Publications

In this paper we present the results of several theoretical models examined in order to explain the observed systematic deviations of the homogeneous nucleation of highly polar substances from the predictions of the classical nucleation theory (CNT). It is found that molecular association in acetronitrile or nitromethane vapor cannot explain the observed higher supersaturations. Similarly, the use of virial coefficient data to obtain a size dependent surface energy correction factor does not reproduce the experimental results. It is shown that orientation of the surface dipoles within the spherical droplets results in higher supersaturations in agreement with the experimental findings. We …

Resonance Raman Spectra Of Chloroperoxidase Reaction Intermediates, Ann Marie G. Sullivan

Theses and Dissertations

Chloroperoxidase is an enzyme that exhibits spectroscopic and structural properties similar to cytochrome P-450. Chloroperoxidase is studied using resonance Raman spectroscopy to characterize the reaction intermediates of the physiological mechanism, known as compounds I and II. Compound I is formed by a two electron oxidation of the resting enzyme and contains an Fe(IV) porphyrin ℼ cation radical. A one electron reduction of compound I produces the compound II intermediate which contains an oxy-ferryl [Fe(IV)=O] iron heme.

Chloroperoxidase is a heme enzyme of substantial interest because of its structural similarity to cytochrome P-450 and because of its diverse reactivity. Chloroperoxidase can …

Observation Of Eliminative Cationic Polymerization Within Van Der Waals Clusters, M. Samy El-Shall, K. E. Schriver

Chemistry Publications

We report the first observation of eliminative cationic polymerization within van der Waals (vdW) clusters following electron impact ionization at pressures of 10⁻⁸ Torr. The elimination reactions of C₂H₃Cl⁺ within the clusters terminate after three successive steps, each involving elimination of HCl or Cl. The results provide a mechanism for the early stages of gas phase cationic polymerization of vinyl chloride and demonstrate the feasibility of using vdW clusters as a means of studying gas phase cationic polymerization.

Imide/Arylene Ether Copolymers, Brian J. Jensen

Theses and Dissertations

Three different series of imide/arylene ether block copolymers were prepared using two different imide blocks and two different arylene ether blocks. Block molecular weights studied were 3110 and 6545 g/mole for each block and all four combinations possible were prepared in each series. Also, several segmented copolymers were prepared by forming the imide segment and the copolymer in the presence of the pre-formed arylene ether block.

Two amine-terminated poly(arylene ether) blocks (ATPAE) were prepared by reacting 1,3-bis(4-fluorobenzoyl)benzene with either 2,2-bis(4-hydroxyphenyl)propane (BPA) or 9,9-bis(4-hydroxyphenyl)fluorene (BPF) and 4-aminophenol. Two anhydride-terminated poly(amic acid) blocks were prepared by reacting 4,4'-oxydianiline (ODA) or 1,3-bis(4-aminophenoxy-4’- benzoyl)benzene …

Reactions Of Substituted Pyridinium Salts With Cyanide; Formation And Metal Complexes Of 2,2'Bis (Hydroxymethyl)-4,-4'Bipyridine, Dorothy N. Eseonu

Theses and Dissertations

The unique combination of properties of bipyridinium salts and their use in biological systems, chemical reactions, and as herbicides in agriculture have made them a discovery of major international importance. The controversy about the position of attack of the cyanide ion on the pyridine ring and the discovery of the formation of unsubstituted bipyridinium salts from the reaction of pyridinium salt with cyanide ion opened a new area of research. The current work involved a study of reactions of substituted pyridinium salts with cyanide ion. The substituted pyridinium salts were prepared by the literature methods. The 2- and 3- cyanopyridinium …

Development Of Solid Substrate Luminescence And Chromatographic Techniques For Chemical Analysis, William J. Long

Theses and Dissertations

Room Temperature Phosphorimetry (RTP) is a sensitive and selective technique which is well suited to the analysis of compounds of environmental and pharmaceutical interests. Absolute sensitivity is generally in the low to subnanograrn range. Selectivity of this technique is due to the fact that only several hundred compounds phosphoresce at room temperature. In these studies attempts are made to gain a greater understanding of the phenomenon of solid substrate room temperature phosphorimetry and to extend the application range of the technique.

This goal is approached through several directions, all leading to a greater understanding of solid substrate luminescence in general, …

Electrochemical And Surface Enhanced Resonance Raman Study Of Heme Proteins At Bare Metal Electrodes, David Edward Reed

Theses and Dissertations

Direct heterogeneous electron transfer reactions between horse heart cytochrome g_and silver electrodes were investigated by electrochemical and spectroelectrochemical methods. The kinetics of these reactions were established as being quasi-reversible, with a formal heterogeneous rate constant (k°'s,h) ranging between 0.18 - 1.5 x 10^-3 cm/s, for both polished and electrochemically roughened silver surfaces. Such reactions were stable and reproducible for over ten hours at room temperature. These results clearly demonstrate that neither electrode surface modification nor the inclusion of mediators is necessary to study electron transfer reactions of heme proteins at metal electrodes.

A crucial factor in obtaining the quasi-reversible …

A Study Of The Heterogeneous Electron Transfer And Dioxygen Binding Reactions Of Myoglobin, Bertha Bauer Cosby King

Theses and Dissertations

Quasi-reversible electron transfer kinetics are reported for sperm whale myoglobin reacting at tin-doped indium oxide electrodes. This reaction was studied by three different electrochemical or spectroelectrochemical methods; cyclic voltammetry (CV), single potential step chronoabsorptometry (SPS/CA) and derivative cyclic voltabsorptometry (DCVA). Kinetic parameters were determined from experiments which followed the purification of the protein,

the pretreatment of the electrode surface, and the removal of dioxygen from the sample solution. A formal heterogeneous electron transfer rate constant, k0′, of 2.6 (±0.5) x 10-5 cm/s and a transfer coefficient, α, of 0.48 (±0.05) were obtained using SPS/CA. These results are shown to correlate …

The Synthesis And Characterization Of Some Thermally Stable Polypyrazoles And Acetylene Terminated Aspartimides, John W. Connell

Theses and Dissertations

Reactions involving the nucleophilic addition cyclization to activated acetylenes have been employed as a novel route to moderate to high molecular weight polymers. Polypyrazoles (PI to P12) have been prepared from the Michael-type addition cyclization of various aromatic dihydrazines to aromatic dipropynones in m-cresol. The aromatic dihydrazines employed were 4, 4'-dihydrazinodiphenyl ether (4,4' -DHDPE), 4,4 '-dihydrazinodiphenylmethane (4, 4'-DHDPM), and 4, 4' -dihydrazinodiphenyl sulfone (4,4'-DHDPS). The dipropynone sutilized were 1,1’- (1,4-phenylene) bis (3-phenyl- 2-propyn-l-one), (l,4 -PPPO), 1,1’ - (1, 3-phenylene) bis (3 -phenyl- 2 -propyn-l-one), (1,3-PPPO), 1,1 '-(1,4 -phenylene) bis (2 -propyn- l-one), (1,4 -PPO), and 1,1’- (1,3 -phenylene) bis (2 …

Electrochemical Investigation Of The Effects Of Temperature, Ph, And Electrolyte On The Electron Transfer Reactions Of Cytochrome C, Kent Brian Koller

Theses and Dissertations

Spectroelectrochemical and electrochemical methods have been used to investigate the characteristics of heterogeneous electron transfer between cytochrome c and indium oxide electrodes. Direct electron transfer between cytochrome c and solid electrodes is of interest due to the interfacial character of electron transfer between the protein and its membrane-bound physiological redox partners. The conformation of ferricytochrome c is affected more by changes in temperature or pH than is its reduced form, ferrocytochrome c. This difference in conformational stability is attributed to the +1 charge of the heme in ferricytochrome c that is largely embedded in the hydrophobic interior of the enzyme. …

Chemical Studies On Oxomolybdenum(Vi,Iv) Complexes As Bioinorganic Models For The Molybdenum Oxidases, James Thomas Lyon Iii

Theses and Dissertations

The synthesis, characterization, and chemical properties of Mo(VI)o₂(5-X-SSP) and Mo(VI)o₂(5-X-SSE), (5-X- SSP²- = 2-((5-X-salicylidene)amino)benzenethiolate; 5-X- SSE^2- = 2-((5-X-salicylidene)amino)ethanethiolate; X = Br, Cl, H, CH₃O), which contain tridentate (ONS) Schiff base ligands is described. The chemical properties of these molybdenum complexes are compared with those which possess tridentate (ONO) Schiff base ligands. Cyclic voltammetry was used to obtain cathodic reduction potentials (E_PC) for the quasi-reversible reduction of the cis-dioxomolybdenum (VI) complexes. Although the reductions are quasi-reversible, trends are observed in E_PC both within series and when different series are …

Magnetic And Mössbauer Study Of Metal‐Zeolite Interaction In Catalysts, Thomas Pannaparayil, M. Oskooie-Tabrizi, C. Lo, L. N. Mulay, G. A. Melson, V. U. S. Rao

Chemistry Publications

Molecular sieve aluminosilicates, such as ZSM‐5 and mordenite, when impregnated with highly dispersed Fe, yield catalysts for the selective conversion of coal‐derived syngas (CO+H₂) to liquid hydrocarbon fuels. Fe performs the primary Fischer‐Tropsch (FT) syngas to yield light olefins which are converted by the acidic (H⁺) and shape‐selective function of the zeolite to high octane gasoline components. The physical aspects of the Fe‐mordenite interaction studied by magnetic measurements, Mössbauer, and IR spectroscopy are reported and correlations with the catalytic properties are drawn. Mordenite samples with [SiO₂/Al₂O₃] ratio in the range …

Effects Of N-Substituents On The Polymerization Properties Of Maleimide, Dilip R. Abayasekara

Theses and Dissertations

The effect of the amide function and the carbethoxy function on the polymerization properties of maleimide are reported. The effects of these functions on homopolymerization and copolymerization (with styrene) were examined. These electron-withdrawing groups appeared to decrease the rate of homopolymerization and increase the rate of copolymerization.

N-carbamylmaleimide and N-carbethoxymaleimide were copolymerized with styrene in 1,4 -dioxane at 60.0° C at different feed ratios to high conversion. Copolymer composition, determined by elemental analysis and 1H NMR, indicated that while 1:1 copolymers were obtained with an equimolar feed ratio, the two systems were not alternating. It is of note that the …

Synthesis Gas Conversion With Zs M-5 Supported Ruthenium Catalysts, Robin Elizabeth Young Eaton

Theses and Dissertations

Some bifunctional ZSM-5 supported ruthenium catalysts (Ru/ ZSM-5) were prepared by an extraction technique employing Ru ₃(C0)₁₂ • The weight percentage Ru ranged from approximately 1% to 8% Ru as determined by Atomic Absorption Spectroscopy. Characterization data employing Infrared (IR) Spectroscopy, X-ray Powder Diffractometry (XRPD), X-ray Photoelectron Spectroscopy (XPS/ESCA), Ion-Scattering Spectrometry (ISS) and Chemisorption were obtained for the catalysts. The data indicated the presence of highly dispersed Ruo₂ particles of less than 60 A on the surface of the as-prepared (AP) catalysts. Calcination of the AP catalysts at 500°C for 24 h increased the particle size of …

Electrochemical Determination Of The Heterogeneous Electron Transfer Kinetics Of Soluble Spinach Ferredoxin, Charlene D. Crawley

Theses and Dissertations

The application of electrochemical techniques to biological systems has become an attractive method for characterizing the redox and electron transfer behavior of biomacromolecules. This study focuses on the role of soluble spinach ferredoxin (Fd) in photosynthesis where it functions as an electron carrier to membrane bound species in the plant chloroplast. An electrochemical model is used where in Fd now serves as a soluble redox species which undergoes oxidation and reduction via electron transfer at an electrode. This type of model is significant in that both the membrane and electrode reactive sites are characterized by charged bilayer interfacial regions which …

Interfacial Electrochemistry Of Cytochrome C And Myoglobin, Edmond F. Bowden

Theses and Dissertations

The interfacial electrochemistry of horse heart cytochrome c was studied at metal and metal oxide electrodes. Sperm whale myoglobin reactions at metal oxide and surface modified electrodes were also investigated. Emphasis was on the measurement and mechanistic interpretation of the heterogeneous electron transfer kinetic parameters for these electrode reactions.

The motivation for this study stems from the fact that some electron transfer proteins, e.g., cytochrome c, transfer electrons heterogeneously in physiological systems. Specific electrodes may, therefore, serve as suitable models for physiological surfaces. Electrode and membrane interfaces are both electrically charged and both have oriented hydration water layers.

The cyclic …

Collisional Depolarization Of State Selected (J,M J ) Bao A 1Σ+ Measured By Optical–Optical Double Resonance, Stuart J. Silvers, Richard A. Gottscho, Robert W. Field

Chemistry Publications

The optical–optical double resonance (OODR) technique is used to investigate the change in magnetic quantum number (M) a state selected molecule undergoes on collision with other molecules. A first linearly polarized dye laser prepares A  ¹Σ⁺BaO(v = 1) in the J = 1, M = 0 sublevel. The extent of collisional transfer to other M sublevels of both J = 1 and J = 2 is then probed by a second polarized dye laser which induces fluorescence from the C  ¹Σ⁺ state. Elastic collisions (ΔJ = 0) between BaO (A …

Direct Determination Of Pentachlorophenol By Differential Pulse Polarography, Albert L. Wade

Theses and Dissertations

Concern over environmental contamination leading to the introduction of pentachlorophenol into human and animal systems has resulted in the need for a rapid and direct method for determining trace concentrations of this highly toxic compound. A direct electrochemical procedure has been developed for determining trace conccentrations of this phenol dovm to 0.27 ppm. This method uses the electrochemical techniques of differential pulse polarography at the dropping mercury electrode, and differential pulse voltammetry at the carbon paste electrode to reduce pentachlorophenol for this determination. Cyclic voltammetry at the hanging mercury drop electrode has been used to characterize the reaction behavior of …

Synthesis Of Tcne And Tcnq Derivatives And The Preparation Of Conducting Polymers, Michael L. Runge

Theses and Dissertations

Tetracyanoethylene and tetracyanoquinodimethane were reacted with various N,N-dimethyl-a, w-alkyldiamines to produce TCNE and TCNQ diamino and monoamino derivatives. NMR and ir spectra of the monoamino derivatives, 1-(N,N-dimethyl-a,w-alkyldiamino)-1,2,2-tricyanoethylenes and 7-(N,N-dimethyl-a,w-alkyldiamino)-7,8,8-tricyanoquinodimethans, indicated that these compounds exhibited strong nitrogen-hydrogen-nitrogen intramolecular hydrogen bonding. This phenomenon was corroborated by molecular weight and preliminary x-ray analyses.

The 1,1-bis(N,N-dimethyl-a,w-alkyldiamino)-2,2-dicyanoethylene and 7,7-bis(N,N-dimethyl-a,m-alkyldiamino)-8,8-dicyanoquinodimethan derivatives were polymerized with a,m-alkyldibromides containing two to six methylene groups to produce the corresponding ionene polymers. Viscosity measurements of the polymers indicated that the TCNE copolymers were generally of higher molecular weight than the corresponding TCNQ copolymers.

The two polymer series were treated with lithium …

The Synthesis Of 4-Spiro-2-Aryloxazolines Of Potential Pharmacological Interest, Paul Waddell Collins

Theses and Dissertations

Numerous and diverse physiological actions are found among 2-oxazoline compounds. No reports of the synthesis or biological testing of 4-spiro-2-aryl-2-oxazolines were found in the literature. On the basis of the known pharmacological activities of certain aza- and diazaspirans, it was felt that 4-spiro-2-aryl-2-oxazolines should possess medicinal activity. In particular, it was reasoned that the combination in a bicyclic spiro structure of the 2-oxazoline ring with rings systems commonly found in synthetic antitussive compounds might result in active antitussive agents.

The aim of this research was the synthesis of a series· of 2-aryl-2-oxazoline-4-spirocyclopentanes and a series of 1'-methyl-2-aryl-2-oxazoline-4-spiro-4’-piperidines. Six members were …