Physical Sciences and Mathematics Commons^™

Dansylation Of Hydroxyl And Carboxylic Acid Functional Groups, Ronald Bartzatt

Chemistry Faculty Publications

Fluorescent labeling of primary and secondary amines using dansyl chloride has been widely used in the past. Its application provides an extremely sensitive means to detect amine functional groups to amounts of less than 1 mg of material. This work describes a method for the dansylation of hydroxyl (–OH) and carboxylic acid (–COOH) functional groups. This technique is demonstrated with ethanol, gamma hydroxy butyric acid (GHB), benzoic acid, and p-chloroaniline. Sensitivity of detection for all compounds are microgram or microliter. For the compounds ethanol and GHB which are liquids at room temperature, as little as 1 ml quantity can be …

Calculation Of 13C Chemical Shifts In Rna Nucleosides: Structure-13C Chemical Shift Relationships, Paolo Rossi, Gerard S. Harbison

Gerard Harbison Publications

Isotropic ¹³C chemical shifts of the ribose sugar in model RNA nucleosides are calculated using SCF and DFT-GIAO ab initio methods for different combinations of ribose sugar pucker, exocyclic torsion angle, and glycosidic torsion angle. Idealized conformations were obtained using structures that were fully optimized by ab initio DFT methods starting with averaged parameters from a collection of crystallographic data. Solid-state coordinates of accurate crystal or neutron diffraction structures were also examined directly without optimization. The resulting ¹³C chemical shifts for the two sets of calculations are then compared. The GIAO-DFT method overestimates the shifts by an average …

Ice Nucleation In Sulfuric Acid And Ammonium Sulfate Particles, Anthony J. Prenni, Matthew E. Wise, Sarah D. Brooks, Margaret A. Tolbert

CUP Faculty Research

Cirrus clouds are composed of ice particles and are expected to form in the upper troposphere when highly dilute sulfate aerosols cool and become supersaturated with respect to ice. In the laboratory we have used Fourier transform infrared spectroscopy to monitor ice nucleation from sulfate particles for relevant compositions of sulfuric acid/water and ammonium sulfate/water aerosols. Measured freezing temperatures are presented as a function of aerosol composition, and results are compared to existing aerosol data. We find that sulfuric acid solution aerosol exhibits greater supercooling than ammonium sulfate solution aerosol of similar weight percent. Ice saturation ratios based on these …

Solubilizing Single Walled Carbon Nanotubes By Direct Reaction With Amines And Alkylaryl Amines, Robert C. Haddon, Jian Chen

Chemistry Faculty Patents

Naked single-walled nanotube carbon metals and semiconductors are dissolved in organic solutions by direct functionalization with amines or alkylaryl amines having an uninterrupted carbon chain of at least 5 and more preferably 9 carbon atoms in length.

Stereoselective One-Pot Synthesis Of Vinylsilanes From Aromatic Aldehydes, Man Lung Kwan, Chiu Yeung, Kerry Breno, Kenneth Doxsee

Man Lung Desmond Kwan

Vinylsilanes serve as convenient vinyl anion equivalents, but procedures for their stereoselective synthesis from aldehydes are scarce. A variety of aromatic aldehydes are converted to the corresponding vinylsilanes in a one-pot procedure involving the addition of (trimethylsilylmethyl)lithium to the aldehyde followed by treatment with Cp2TiCH2·AlMe2Cl (‘Tebbe's reagent’). Halide and alkoxide substituents are tolerated, and (E)-vinylsilanes are formed exclusively in good yield.

Effect Of Carrier-Gas Pressure On Barrier To Nucleation: Monte Carlo Simulation Of Water/Nitrogen System, K.J. Oh, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Carrier gases are used in most nucleation experiments for releasing the latent heat generated during vapor condensation. In the analysis of experimental data it is often assumed that the carrier gas is inert and would not participate in the nucleation process of the target gas. Several recent nucleation experiments show that the influence of carrier gases to nucleation rate is not negligible under certain conditions. To gain more insight into the carrier-gas effect, we carry out Monte Carlo simulation to compute the free energy of formation of water clusters in the presence of a nitrogen carrier gas. At fixed temperature …

Adsorption And Decomposition Of Nickelocene On Ag(100): A High-Resolution Electron Energy Loss Spectroscopy And Temperature Programmed Desorption Study, D. L. Pugmire, C. M. Woodbridge, N. M. Boag, Marjorie Langell

Marjorie A. Langell Publications

Nickelocene adsorption and decomposition on the Ag(100) surface were studied with temperature programmed desorption and high resolution electron energy loss spectroscopy. At monolayer coverages on the relatively inert Ag(100) surface at 175 K, nickelocene physisorbs molecularly, with its molecular axis perpendicular to the surface plane. Nickelocene begins decomposing to adsorbed cyclopentadienyl and nickel at 225 K. Molecular desorption is only observed from multilayer material, at 210 K, or from the first monolayer if adjacent surface sites for decomposition are not available. The cyclopentadienyl decomposes through disproportionation to cyclopentadiene, which desorbs, and adsorbed nickel and carbon fragments on the Ag(100) surface …

Rayleigh And Raman Scattering, David W. Ball

Chemistry Faculty Publications

Details the molecular aspect of Raman spectroscopy. Overview on the molecular absorption process; Information on Rayleigh scattering; Effects of the Raman scattering.

Simulations Of Ice And Liquid Water Over A Range Of Temperatures Using The Fluctuating Charge Model, Steven W. Rick

Chemistry Faculty Publications

The temperature dependence of the thermodynamic and dynamical properties of liquid water using the polarizable fluctuating charge (FQ) model is presented. The properties of ice Ih, both for a perfect lattice with no thermal disorder and at a temperature of 273 K, are also presented. In contrast to nonpolarizable models, the FQ model has a density maximum of water near 277 K. For ice, the model has a dipole moment of the perfect lattice of 3.05 Debye, in good agreement with a recent induction model calculation. The simulations at 273 K and the correct density find that thermal motion decreases …

Effects Of External Electric Field On The Interfacial Properties Of Weakly Dipolar Fluid, V.B. Warshavsky, T.V. Bykov, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

In the framework of modified mean-field density-functional theory, effects of a uniform electric field on the interfacial properties of a model dipolar fluid [Teixeira and Telo da Gama, J. Phys.: Condens. Matter 3, 111 (1991)] are studied. Both density and orientational order-parameter profiles of the planar vapor-liquid interface are obtained as a function of the field strength. For the dipolar fluids with reduced dipole moment μ₀^*0^*E*/T*!1) can shift the surface tension by few percent. We also find that the electric field actually reduces the thermodynamical surface tension but enhances the mechanical surface …

Synthons And Design In Metal Phosphates And Oxalates With Open Architectures, Chintamani Nagesa Ramachandra Rao, Srinivasan R. Natarajan, Amitava Choudhury, Sharma Neeraj, Ramamurthy Vaidhyanathana

Chemistry Faculty Research & Creative Works

We briefly describe the structures of open-framework metal phosphates with different dimensionalities, such as the one-dimensional linear-chain and ladder structures, two-dimensional layer structures and three-dimensional structures with channels. We demonstrate the role of the zero-dimensional four-membered ring monomer and of the one-dimensional ladder structure as the starting building units or synthons involved in the formation of the complex architectures. Thus, we show how the one-dimensional ladder structure transforms to two- and three-dimensional structures under mild conditions. The two-dimensional layer structures also transform to three-dimensional structures, while the zero-dimensional monomer transforms to layered and three-dimensional structures under ordinary reaction conditions. These …

Probing The Relative Timing Of Hydrogen Abstraction Steps In The Flavocytochrome B2 Reaction With Primary And Solvent Deuterium Isotope Effects And Mutant Enzymes, P. Sobrado, S. C. Daubner, P. F. Fitzpatrick

Chemistry Faculty Research & Creative Works

Flavocytochrome b2 catalyzes the oxidation of lactate to pyruvate. Primary deuterium and solvent kinetic isotope effects have been used to determine the relative timing of cleavage of the lactate O - H and C - H bonds by the wild-type enzyme, a mutant protein lacking the heme domain, and the D282N enzyme. The DVmax and D(V/Klactate) values are both 3.0 with the wild-type enzyme at pH 7.5 and 25 °C, increasing to about 3.6 with the flavin domain and increasing further to about 4.5 with the D282N enzyme. Under these conditions, the D20Vmax values are 1.38, 1.18, and 0.98 for …

Process For Immobilizing Waste Using Bagasse (Us Patent 6174275), Michael A. Janusa

Faculty Publications

No abstract provided.

Tectorna: Modular Assembly Units For The Construction Of Rna Nano-Objects, Neocles B. Leontis, Luc Jaeger, Eric Westhof

Chemistry Faculty Publications

Structural information on complex biological RNA molecules can be exploited to design tectoRNAs or artificial modular RNA units that can self-assemble through tertiary interactions thereby forming nanoscale RNA objects. The selective interactions of hairpin tetraloops with their receptors can be used to mediate tectoRNA assembly. Here we report on the modulation of the specificity and the strength of tectoRNA assembly tin the nanomolar to micromolar range) by variation of the length of the RNA subunits, the nature of their interacting motifs and the degree of flexibility of linker regions incorporated into the molecules. The association is also dependent on the …

An Approach For Clarification Of The Mechanism Of Inactivation Of Ribonucleotide Reductases With 3'<¹⁷O>-Labeled 2'-Azido-2'-Deoxynucleotides, Saiful Mahmud Chowdhury

FIU Electronic Theses and Dissertations

Inactivation of ribonucleotide reductases by 2'-azido-2'-deoxynucleotides is accompanied by appearance of new EPR signals for a nitrogen-centered radical. The structure of this elusive nitrogen-centered radical has been studied extensively and shown to be derived from azide moiety. Synthesis of 3'[¹⁷ O]-labeled 2'-azido-2'-deoxyuridine-5'- diphosphate was targeted in this research. Such a labeled analogue should perturb the EPR spectrum in predictable fashion, and the hyperfine interaction between the free electron and the ¹⁷O nucleus should allow the choice between the recently proposed structures of this elusive radical (Van Der Donk, W. A. et al. J Am. Chem. Soc. 1995 …

Semiclassical Application Of The Mo”Ller Operators In Reactive Scattering, Sophya Garashchuk, John C. Light

Faculty Publications

Mo\ller operators in the formulation of reaction probabilities in terms of wave packet correlation functions allow us to define the wave packets in the interaction region rather than in the asymptotic region of the potential surface. We combine Mo\ller operators with the semiclassical propagator of Herman and Kluk. This does not involve further approximations and can be used with any initial value representation (IVR) semiclassical propagator. Time propagation in asymptotic regions of the potential due to Mo\ller operators reduces the oscillations of the propagator integrand and improves convergence of the results with respect to the number of trajectories. The effectiveness …

High-Performance Liquid Chromatographic And Capillary Electrophoretic Enantioseparation Of Plant Growth Regulators And Related Indole Compounds Using Macrocyclic Antibiotics As Chiral Selectors, F. Hui, K. H. Ekborg-Ott, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

Enantioseparation of plant growth regulators, such as 3-(3-indolyl)-butyric acid, abscisic acid and structurally related molecules including a variety of substituted tryptophan compounds, has been achieved by HPLC and/or CE. The covalently bonded macrocyclic antibiotics, teicoplanin, ristocetin A and vancomycin, were used as chiral stationary phases (CSPs) in HPLC. Most of the racemates were baseline resolved in the reversed-phase mode (EtOH-H2O) using the teicoplanin CSP. The chiral recognition mechanism is discussed in regard to the structure of the analytes. In CE, the three aforementioned macrocyclic antibiotics were used as chiral additives in a phosphate run buffer. The effect of pH and …

Atomically Resolved Single-Walled Carbon Nanotube Intramolecular Junctions, Min Ouyang, Jin-Lin Huang, Chin Li Cheung, Charles M. Lieber

Barry Chin Li Cheung Publications

Intramolecular junctions in single-walled carbon nanotubes are potentially ideal structures for building robust, molecular-scale electronics but have only been studied theoretically at the atomic level. Scanning tunneling microscopy was used to determine the atomic structure and electronic properties of such junctions in single-walled nanotube samples. Metal-semiconductor junctions are found to exhibit an electronically sharp interface without localized junction states, whereas a more diffuse interface and low-energy states are found in metal-metal junctions. Tight-binding calculations for models based on observed atomic structures show good agreement with spectroscopy and provide insight into the topological defects forming intramolecular junctions. These studies have important …

Simple Relationships For The Estimation Of Melting Temperatures Of Homologous Series, James S. Chickos, Gary Nichols

James Chickos

No abstract provided.

Tandem 4+3 Cycloaddition/Nucleophilic Trapping Reactions Of Butyne-1,4-Diether Dicobalt Hexacarbonyl Complexes, Yafan Lu, James R. Green

Chemistry and Biochemistry Publications

Butyne-1,4-diether hexacarbonyldicobalt complexes 1 undergo Lewis acid mediated 4+3 cycloadditions with allylsilanes, incorporating halide from the Lewis acid to give halocycloheptynes 3, 6, 7. A phenyl group may be incorporated in place of the halogen (to give 8) by use of benzene as solvent and with B(C6F5)(3) as the Lewis acid; chlorobenzene and toluene also participate in the process.

Cycloheptenyne Dicobalt Hexacarbonyl Complexes By Ring Closing Metathesis, James R. Green

Chemistry and Biochemistry Publications

Hexacarbonyldicobalt complexes of cycloheptenynes (4) may be prepared by the ring closing metathesis of the corresponding acyclic dienes (2) using Grubbs' catalyst, (Cy3P)(2)Cl2Ru=CHPh. A cyclooctenyne complex (8) has also been prepared in the strictly analogous manner.

Halogen Oxidation Reactions Of (C5ph5)Cr(Co)3 And Lewis Base Addition To [(C5ph5)Cr(Μ-X)X]2: Electrochemical, Magnetic, And Raman Spectroscopic Characterization Of [(C5ph5)Crx2]2 And (C5ph5)Crx2(Thf) (X = Cl, Br, I). X-Ray Crystal Structure Of [(C5ph5)Cr(Μ-Cl)Cl]2, Marc A. Hutton, James C. Durham, Robert W. Grady, Brett E. Harris, Carter S. Jarrell, J. Matthew Mooney, Michael Castellani, Arnold L. Rheingold, Ulrich Kölle, Brenda J. Korte, Roger D. Sommer, Gordon T. Yee, J. Matthew Boggess, Roman S. Czernuszewicz

Chemistry Faculty Research

The 17-electron complex (C5Ph5)Cr(CO)3 reacts with halogens (C6H5I•Cl2, Br2, and I2) in C6H6 to yield the dimeric oxidation products [(C5Ph5)Cr(m-X)X]2 as thermally stable solids. Reactions with other chlorinating agents similarly yield [(C5Ph5)CrCl2]2. An X-ray crystal structure of [(C5Ph5)Cr(m-Cl)Cl]2 was obtained. The magnetic properties of the Cl₂ bridged dimer have been determined and modeled using the usual isotropic hamiltonian which yields J/k = –30 K. Low-temperature (77 K) Raman spectra of solid [(C5Ph5)CrX2]2 (X = Cl, I) allow assignments to be made for the metal-ring and metal halogen stretching modes in the low frequency region (< 600 cm-1). Tetrahydrofuran (THF) cleaves these dimers to yield complexes of the form (C5Ph5)CrX2(THF).

Some Notable Discoveries In Organosilicon Chemistry: Proceedings Of The History And Retrospective Session Of The 34th Organosilicon Symposium (2001), Adrian G. Brook, Robert West, Kim M. Baines, William B. Herdle, Larry H. Wood, Kenrick M. Lewis, George H. Wagner, Bernard Kanner

Proceedings

The 34th Organosilicon Symposium at White Plains, NY, in 2001 featured a History and Retrospective Session, during which invited speakers from academic and industrial laboratories recounted the path to some significant 20th century discoveries in organosilicon chemistry.

• The Si=C Story: The Way it Happened, Adrian G. Brook (University of Toronto)

• The Discovery of Stable Disilenes and Silylenes, Robert West (University of Wisconsin)

• Yellow Fever: The Story Behind the Synthesis of Germasilenes, Kim M. Baines (University of Western Ontario)

• Direct Synthesis of Tris(dimethylamino)silane, William B. Herdle (OSi Specialties, formerly of Union Carbide Corporation)

• Discovery of Tin and Phosphorus Effects on …

Assembly And Characterization Of Sams Formed By The Adsorption Of Alkanethiols On Zinc Selenide Substrates, Alison Noble, Ralph G. Nuzzo

Educator Scholarship

Alkanethiols HS(CH₂)_nCH₃ (n = 7, 11, 15, 17) and the hydroxy functional thiol HS(CH₂)₁₂OH are shown to adsorb from solution onto zinc selenide crystals and form well-organized monolayers. The chemisorption of these organosulfur compounds has been studied using transmission Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and surface wetting properties. FTIR indicates that the longer chain alkanethiols (n = 15, 17) form well-defined SAMs with crystalline-like conformations of the chains within the monolayers. As the chain length decreases, there is less conformational order …

Thermodynamic Investigation Of The Si7 And Si8 Clusters By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich

Chemistry Faculty Publications

The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of the Si[sub 7] and Si[sub 8] clusters under equilibrium conditions above liquid silicon, contained in a boron nitride liner inside a graphite Knudsen cell. Gaussian 2 (G2) theory and B3LYP density functional method were employed to determine the geometry, the vibrational frequencies, and the binding energy of the Si[sub 8] cluster. From the all-gas analyzed equilibria the following atomization enthalpies, Δ[sub a]H[sub 0][sup o](Si[sub n]), and enthalpies of formation, Δ[sub f]H[sub 298.15][sup o](Si[sub n]), in kJ mol-1, have been obtained: Si[sub 7], 2381±36 and …

Structure And Thermodynamic Stability Of The Osc And Osc2 Molecules By Theoretical Calculations And By Knudsen Cell Mass Spectrometry, Giovanni Meloni, L M. Thomson, Karl A. Gingerich

Chemistry Faculty Publications

Knudsen cell mass spectrometric equilibrium measurements together with theoretical computations have been employed to gain structural and thermodynamic information of the OsC and OsC[sub 2] molecules. Several levels of theory have been applied to determine the structures, molecular parameters, and physico-chemical properties of OsC(g) and OsC[sub 2](g), and their singly charged ions. Complete active space self-consistent field (CASSCF) calculations were performed on the apparent [sup 3]Σ[sup -] ground state and first [sup 3]Δ excited state of OsC. From the analyzed gaseous equilibria and the thermal functions calculated from the computed molecular parameters, the following atomization enthalpies, Δ[sub a]H[sub 0][sup o](OsC,g) …

Solidification/Stabilization Of Lead With The Aid Of Bagasse As An Additive To Portland Cement, Michael A. Janusa

Faculty Posters

No abstract provided.

Dispersion Of Potassium Nitrate And The Resulting Strong Basicity On Zirconia, Ying Wang, Wenyu Huang, Yuan Chun, Jia Rong Xia, Jian Hua Zhu

Wenyu Huang

A novel solid superbase is derived from zirconia-supported potassium nitrate. Dispersion and decomposition of potassium nitrate on zirconia were investigated and compared with that on alumina to explore the effect of the support on the preparation of solid strong bases. Spontaneous dispersion capacity of KNO3 on ZrO2 was found to be 8.1 K+ nm-2, very close to that of a vacant site on ZrO2. An unusually strong basicity was generated on ZrO2 through decomposition of the loaded KNO3 that began around 613 K, enhancing the catalytic activity of ZrO2 in cis-but-2-ene isomerization at 273 K. Moreover, KNO3/ZrO2 samples, except 34% …

Synthesis And Characterization Of Potassium-Modified Alumina Superbases, Ying Wang, Jian Hua Zhu, Wenyu Huang

Wenyu Huang

Novel solid superbases can be prepared by dispersing potassium salts such as K2CO3 and KHCO3 on alumina followed by thermal treatments. The resulting materials show an extremely high activity in the isomerization of cis-but-2-ene at 0°C and possess base strength of at least H− = + 26.5. X-Ray diffraction (XRD) and Raman spectra of K2CO3 or KHCO3 modified alumina reveal the formation of potassium hydroalumina carbonate, which is the precursor of active species. Decomposition of potassium salts on alumina has been studied by use of thermal gravimetric differential thermal analysis (TG-DTA) and temperature programmed decomposition-mass spectrometry (TPDE-MS). Two CO2 evolution …

Propagating Conformational Changes Over Long (And Short) Distances In Proteins, Edward Yu, Daniel E. Koshland Jr.

Edward Yu

The problem of the propagation of conformational changes over long distances or through a closely packed protein is shown to fit a model of a ligand-induced conformational change between two protein states selected by evolution. Moreover, the kinetics of the pathway between these states is also selected so that the energy of ligand binding and the speed of the transition between conformational states are physiologically appropriate. The crystallographic data of a wild-type aspartate receptor that has negative cooperativity and a mutant that has no cooperativity but has native transmembrane signaling are shown to support this model.