Organic Chemistry Commons^™

Hplc Of Monolayer-Protected Gold Nanoclusters, Victoria L. Jimenez,, Michael C. Leopold, Carolyn Mazzitelli, James W. Jorgenson, Royce W. Murray

Chemistry Faculty Publications

Polydisperse samples of Au nanoparticles protected with monolayers of hexanethiolate ligands (C6 MPCs) and with mixed monolayers of hexanethiolate and mercaptounde- canoic acid (C6/MUA MPCs) have been chromatographically separated using C8 120-Å columns and acetone/toluene mobile phase. The spectral details of eluted peaks and of quantized double-layer charging features in the differential pulse voltammetry of collected fractions were used to show that the elution orders of C6 MPC mixtures and of C6/MUA MPC mixtures were different. For C6 MPCs, the smallest MPCs were eluted first, whereas the smallest C6/MUA MPCs were eluted last. The reversal of order of elution was …

A Comparison Of The Low Mode And Monte Carlo Conformational Search Methods, Carol A. Parish, Rosina Lombardi, Kent Sinclair, Emelyn Smith, Alla Goldberg, Melissa Rappleye, Myrianne Dure

Chemistry Faculty Publications

The Low Mode (LM) and Monte Carlo (MC) conformational search methods were compared on three diverse molecular systems; (4R, 5S, 6S, 7R)-hexahydro-5,6-dihydroxy-1,3,4,7-tetrakis(phenylmethyl)-2H-1,3-diazapin-2-one (1), 2-methoxy-2-phenyl-2-triflouromethyl-N-α-methyl benzyl propanamide (2) and a trimeric 39-membered polyazamacrolide (3). We find that either method, or a combination of the methods, is equally efficient at searching the conformational space of the smaller molecular systems while a 50:50 hybrid of Low Mode and Monte Carlo is most efficient at searching the space of the larger molecular system.

Analysis Of Fuel Additives And Impurities In Gasoline, Nicholas Lentz

Honors Capstones

Capstone submitted as a graduation requirement for the BSU Honors Program.

Styrene Monomer Solubility In Artificial And Natural Seawaters Of The Lower Chesapeake Bay, Eric Joseph Miller

Chemistry & Biochemistry Theses & Dissertations

Used for making a variety of plastic products, styrene monomer is an aromatic hydrocarbon frequently shipped in bulk quantities through the Port of Hampton Roads, Virginia. Despite its common use around the world and its high aquatic toxicity, little research has been conducted on the chemical's aqueous solubility and reactions during a major spill. In this study, the solubility of styrene monomer was measured in artificial seawater and natural waters collected from four sites on the lower Chesapeake Bay and Elizabeth River. The samples represented a range of different water chemistries in terms of salinity (13.8 — 29.0%) and the …

The Influence Of Gold Substrate Topography On The Voltammetry Of Cytochrome C Adsorbed On Carboxylic Acid Terminated Self-Assembled Monolayers, Michael C. Leopold, Edmond F. Bowden

Chemistry Faculty Publications

Interfacial investigations of a protein monolayer electrochemical system, equine cytochrome c (cyt c) adsorbed to carboxylic acid terminated self-assembled monolayer (COOH SAM) modified gold electrodes, were performed. Electrochemical, spectroscopic, and scanning probe microscopy techniques were utilized to explore the influence of gold topography in the cyt c/COOH SAM/gold system. COOH SAMs were prepared from 14-mercaptotetradecanoic acid and 11-mercaptoundecanoic acid on a variety of substrates including evaporated, bulk, single crystal, and epitaxially grown gold on mica. These substrates encompassed a wide range of surface roughness. As the topography of the gold became smoother, SAMs exhibited an increased ability to …

Sythesis And Characterization Of [(C5r5) M (Co)2 (L2)]+: R=H, Me And Ph; M=Cr And Mo; L2=Dmpe And Dppe, Brian Dearman

Theses, Dissertations and Capstones

For two decades much research has been concentrated on open-shell transition metal complexes as chemical intermediates. To date, most efforts have concentrated on electron deficient, 17-electron (17e) compounds; however past research has shown that electronically supersaturated, 19-electron (19e) complexes can also participate as intermediates in many reactions. Yet, excluding (C₅ H₅)Fe(C₆ H₆) type complexes, very few of these compounds have been prepared.^2,3 To better understand the nature of 19e, the preparation of another series of compounds is desirable.

The addition of the bidentate Lewis bases 1,2- bis(dimethylphosphino)ethane (dmpe) or 1,2-bis(diphenylphosphino)ethane (dppe) to a …

Chemical Composition Of Particles Of D < 0.20 Mu In The Lower Stratospheric Aerosol, Spring 1993, Joseph D. Scott, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

The majority of the mass of stratospheric aerosol collected during the spring of 1993 consisted principally of particles of d >0.20 mu containing a mixture of H2SO4 and (NaK)2SO4. However, the composition of the more numerous particles with d< 0.2 mu was very different. X-ray emission spectra (EDS) of individual particles indicated that there were three different chemical populations of small particles. The most numerous population was almost all C with only traces of S and Na. The second population contained metal sulfates and chlorides, possibly accreted to a C-containing matrix. The third population consisted of S- and Cl- containing species and trace amounts of Na and K ions. The number of equivalents of metal ion was much less than that of S and Cl species, indicating that most of the S and Cl was not ionic, but was covalently bonded, perhaps to a C matrix.

Time-Dependent Density Functional Theory Investigation Of The Ground And Excited States Of Coumarins 102, 152, 153, And 343, Robert J. Cave, Edward W. Castner Jr.

All HMC Faculty Publications and Research

We present calculations of various properties of the ground and excited electronic states of coumarins 102, 152, 153, and 343. Using density functional theory (DFT) and time-dependent density functional theory (TDDFT), we examine the excitation energies to the S₁ and S₂ states, the ground and excited-state dipole moments, and the lowest ionization potentials of these coumarins. In the case of C153, we locate two distinct S₀ minima due to differing conformations of the julolidyl ring structure and compare properties for the syn and anti conformers. For C343, we examine the possibility of proton transfers in the ground …

Synthesis And Chemistry Of Naphthalene Annulated Trienyl Iron Complexes: Potential Anticancer Dna Alkylation Reagents, Traci Means

Inquiry: The University of Arkansas Undergraduate Research Journal

Iron complex chemistry that opens a new door to the medicinal and pharmaceutical worlds is the aim of this research. Specifically, ortho-quinone methide moieties are intermediates in several antitumor drugs and have been identified as bioreductive alkylators of DNA. In our research, a class of iron compounds has been targeted to resemble these quinone methides. It is hoped that these new compounds could be modified to provide a window of opportunity toward the discovery of a selective mode of drug delivery. We have focused our efforts on generating a reactive transition metal complexed 5-membered ring analog of o-quinone methide based …

Pyridoimidazolium Cationic Dyes: Theory, Synthesis, And Sub-Cellular Localization, Robert William Rambacher

Theses, Dissertations and Capstones

(PICs, Figure 1) are a new class of fluorescent dyes which are prepared by an exceedingly flexible methodology. Using computational chemical methods, the excitation and emission maxima of these dyes were simulated. This was best accomplished through geometry optimization (MM+) followed by calculating the electronic spectrum with ZINDO/S. This protocol has been found to be effective and has the potential to greatly streamline the design of new longer wavelength dyes. Several new longer wavelength dyes have now been identified as synthetic targets.

The presence of amino groups on a known fluorescent ring system is well established to markedly affect the …

Theoretical Investigation Of The Ground And Excited States Of Coumarin 151 And Coumarin 120, Robert J. Cave, Kieron Burke, Edward W. Castner Jr.

All HMC Faculty Publications and Research

We present calculations of various properties of the ground and excited states of Coumarins 151 and 120. These and related coumarins are important in investigating ultrafast solvation processes in liquids and complex solutions as well as being important acceptors in model electron-transfer systems. We calculate the following:  (1) the electronic excitation energies to several low-lying singlet states, (2) ground and excited-state dipole moments, (3) solvation effects on excitation energies, and (4) the properties of single Coumarin 151-water complexes. We test our Time-Dependent Density Functional Theory (TDDFT) calculations against CASSCF, CASPT2 (both single and multistate versions), CIS, and ZINDO. Using TDDFT, …

Multistate Effects In Calculations Of The Electronic Coupling Element For Electron Transfer Using The Generalized Mulliken−Hush Method, Michael Rust '01, Jason Lappe '00, Robert J. Cave

All HMC Faculty Publications and Research

A simple diagnostic is developed for the purpose of determining when a third state must be considered to calculate the electronic coupling element for a given pair of diabatic states within the context of the generalized Mulliken−Hush approach (Chem. Phys. Lett. 1996, 275, 15−19). The diagnostic is formulated on the basis of Löwdin partitioning theory. In addition, an effective 2-state GMH expression is derived for the coupling as it is modified by the presence of the third state. Results are presented for (i) a model system involving charge transfer from ethylene to methaniminium cation, (ii) a …

Applications Of Bismuth(Iii) Compounds In Organic Synthesis, Ram Mohan, Nicholas Leonard, Laura Wieland

Scholarship

No abstract provided.

Bismuth Triflate Catalyzed Allylation Of Acetals: A Simple And Mild Method For Synthesis Of Homoallyl Ethers, Ram Mohan, Laura Wieland, Herbert Zerth

Scholarship

The allylation of acetals using allyltrimethylsilane is efficiently catalyzed by bismuth triflate (1.0 mol%). The reaction proceeds smoothly at room temperature to afford the corresponding homoallyl ether in good yield. The mild reaction conditions, the low toxicity of bismuth salts, and the high catalytic efficiency of the system make this procedure particularly attractive for large-scale synthesis.

Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton

Journal of the Arkansas Academy of Science

A simple, rapid, and effective method for the extraction of fifteen organochlorine and organophosphorus pesticides based on the use of solid phase Bond Elut C-18 cartridges was studied as an alternative method to those based on extraction with organic solvents. Solid phase extraction is an attractive chromatographic sample preparation technology that reduces analysis time, costs, labor, and solvent consumption relative to traditional liquid/liquid extraction methods. The sample recoveries with the use of solid phase extractions were excellent for most pesticides. Analyte concentration by a factor as great as 1000-fold was achieved readily. The adsorbed pesticides were eluted from the solid …

Adsorptive Immobilization Of Cytochrome C On Indium/Tin Oxide (Ito): Electrochemical Evidence For Electron Transfer-Induced Conformational Changes, Asma El Kasmi, Michael C. Leopold, Ryan Galligan, Rebecca T. Robertson, S. Scott Saavedra, Kacem El Kacemi, Edmond F. Bowden

Chemistry Faculty Publications

The adsorptive immobilization and electrochemistry of horse and yeast cytochrome c on indium/tin oxide (ITO) electrodes is reported. Near-monolayer coverage was achieved in pH 7 phosphate buffers of ionic strength equal to 10 and 50 mM, respectively, for the horse and yeast species. The layers exhibit very well-behaved voltammetry and are stable on the timescale of hours to days. Cyclic voltammetry revealed quasireversible behavior that is a product of both electron transfer (ET) kinetics and ET-induced conformational changes. A square scheme mechanism linking the redox states and the conformational states is proposed. Using a simple ET kinetic model that adequately …