Chemistry Commons^™

Determination Of Barbituric Acid, Utilizing A Rapid And Simple Colorimetric Assay, Ronald Bartzatt

Chemistry Faculty Publications

Barbituric acid is widely used in the manufacturing of plastics, textiles, polymers, and pharmaceuticals. Three assay methods are presented, which can utilize either aqueous or solid samples. The detection of as little as 10 μg of barbituric acid can be accomplished, either as an aqueous or solid sample, when using micro reaction tubes. The red–violet endpoint is easily discerned and results upon the formation of a violuric acid derivative. A Spot Test protocol is described which allows for a positive/negative indication of barbituric acid presence. The Spot Test is sensitive to as little as 18.75 μg/ml of barbituric acid. The …

44th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 44th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Denver, Colorado, July 28 - August 1, 2002.

Heterogeneous Nucleation On Mesoscopic Wettable Particles: A Hybrid Thermodynamic/Density-Functional Theory, T.V. Bykov, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A hybrid thermodynamic and density-functional theory for heterogeneous nucleation on mesoscopic wettable particles is developed. The nonlocal density-functional theory (DFT) is on basis of the weighted-density approximation (WDA) of Tarazona. The model system consists of a Lennard-Jones (LJ) fluid and a 9–3 LJ wall for the solid particle. Effects of the droplet curvature and compressibility are accounted for in the theory. A by-product of this work is the calculation of the Tolman length using the WDA-DFT (Appendix A). Important characteristics of the heterogeneous nucleation, including the chemical potential of the liquid condensate, the free energy of droplet formation, and the …

A Model For Mechanochemical Transformations: Applications To Molecular Hardness, Instabilities, And Shock Initiation Of Reaction, Tadeusz Luty, Piotr Ordon, Craig J. Eckhardt

Craig J. Eckhardt Publications

A basic theoretical structure for mechanochemical transformations based on prior models for solid-state reactions and HOMO–LUMO (highest occupied molecular orbital–lowest unoccupied molecular orbital) gap closing produces the concept of distortion-induced molecular electronic degeneracy (DIMED) of the highest occupied and lowest unoccupied molecular orbitals of an energetic molecule. Both intermolecular and intramolecular charge transfer are involved. The resulting distortion-induced local instability, a mechanochemical effect, leads to chemical transformations and can be analyzed by renormalization of the molecular hardness through the molecular deformation energy. Linear combinations of normal modes are shown to be useful for description of the mechanically induced reaction path. …

Preprogramming Of Porphyrin−Nucleic Acid Assemblies Via Variation Of The Alkyl/Aryl Substituents Of Phosphonium Tetratolylporphyrins, Pavel Kubat, Kamil Lang, Vladimir Kral, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Cationic alkyl/arylphosphonium meso-tetratolylporphyrins aggregate in an aqueous solution to form H-aggregates, J-aggregates, and long-range assemblies. The ratio between the monomer and various types of aggregates can be controlled by the substitution in the phosphonium units and by the ionic strength. A trimethylphosphonium derivative is predominantly monomeric, dimethylphenylphosphonium forms monomers as well as low-molecular-weight H- and J-aggregates, triphenylphosphonium forms mainly H- and J-aggregates, and tri(n-butyl)phosphonium forms mainly long-range assemblies. Porphyrin monomers associate with calf thymus DNA (binding constant Kb approximate to 10(7) M-1) and oligonucleotides (K-b approximate to 10(5-)10(6) M-1). The large size of the meso-substituents prevents the intercalation between base …

In-Situ X-Ray-Absorption Spectroscopy Study Of Hydrogen Absorption By Nickel-Magnesium Thin Films, B. Farangis, Ponnusamy Nachimuthu, T. J. Richardson, J. L. Slack, Rupert C. Perera, Eric M. Gullikson, Dennis W. Lindle, M. Rubin

Chemistry and Biochemistry Faculty Research

Structural and electronic properties of co-sputtered Ni-Mg thin films with varying Ni to Mg ratio were studied by in-situ x-ray absorption spectroscopy in the Ni L-edge and Mg K-edge regions. Co-deposition of the metals led to increased disorder and decreased coordination around Ni and Mg compared to pure metal films. Exposure of the metallic films to hydrogen resulted in formation of hydrides and increased disorder. The presence of hydrogen as a near neighbor around Mg caused a drastic reduction in the intensities of multiple scattering resonances at higher energies. The optical switching behavior and changes in the x-ray spectra varied …

Non-Dipolar Electron Angular Distributions From Fixed-In-Space Molecules, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, E. Shigemasa, K. Le Guen, D. Ceolin, C. Miron, N. Leclercq, P. Morin, Marc Simon, P. W. Langhoff

Environmental Studies Faculty Publications

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N₂. Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.

Synthetic Studies Directed Toward The Phorboxazoles: Preparation Of The C3–C15 Bisoxane Segment And Two Stereoisomers, Patrick Bernard Greer, William A. Donaldson

Chemistry Faculty Research and Publications

A synthetic approach to the C3–C15 segment of the cytotoxic marine metabolite phorboxazoles is described. This segment consists of a methylene linked bisoxane structure. The first pyran ring was constructed by a Lewis acid catalyzed diene–aldehyde cyclocondensation. The β-C-glucoside substitution pattern of this ring was established by a stereoselective allylation. Ozonolysis of vinyl group and enantioselective allylation of the racemic aldehyde generated two separable homoallylic alcohols (−)-22 and (+)-23. The Mosher's esters of each alcohol were determined to be >90% de. Reaction of (−)-22 with acryloyl chloride, followed by ring closing metathesis gave the …

Electron Hopping Conductivity And Vapor Sensing Properties Of Flexible Network Polymer Films Of Metal Nanoparticles, Francis P. Zamborini, Michael C. Leopold, Jocelyn F. Hicks, Pawel J. Kulesza, Marcin A. Malik, Royce W. Murray

Chemistry Faculty Publications

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and ω-carboxylate alkanethiolate monolayers, linked together in a network polymer by carboxylate-Cu2+-carboxylate bridges, exhibit electronic conductivities (σEL) that vary with both the numbers of methylene segments in the ligands and the bathing medium (N2, liquid or vapor). A chainlength-dependent swelling/contraction of the film's internal structure is shown to account for changes in σEL. The linker chains appear to have sufficient flexibility to collapse and fold with varied degrees of film swelling or dryness. Conductivity is most influenced (exponentially dependent) by the chainlength of the nonlinker (alkanethiolate) ligands, a result consistent …

Synthesis Of The Abc Ring System Of Azaspiracid. 2. A Systematic Study Into The Effect Of C16 And C17 Substitution On Bis-Spirocyclization, Rich G. Carter, David E. Graves, Melissa A. Gronemeyer, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

(matrix presented) A systematic study into the effect of C16 and C17 substitution on the stereochemical outcome of bis-Spiro cyclization to form the ABC ring system of azaspiracid is disclosed. Successful construction of the natural 10R,13R bis-spirocyclic stereochemistry has been accomplished on the C16 benzyloxy-containing precursor.

Hydrogen-Induced Embrittlement Of Candidate Target Materials For Applications In Spallation-Neutron-Target Systems: Annual Progress Report (May 2001 – May 2002), Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the effect of hydrogen on environment-assisted cracking of candidate target materials for applications in spallation-neutron-target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization are martensitic stainless steels including Alloy HT-9, Alloy EP 823 and Type 422 stainless steel. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of these materials are being evaluated in environments of interest using tensile specimens under constant load and slow-strain-rate (SSR) conditions. Further, the localized corrosion behavior of these alloys …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics: Quarterly Progress Report 03/16/02- 06/15/02, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the AAA proposed application. Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with very limited density. Scientists have noticed that the concentration of oxygen dissolved in the liquid alloy could control the corrosion rate of steels exposed to Pb or Pb-Bi. At high oxygen concentration, …

Evaluation Of Fluorapatite As A Waste-Form Material, Dennis W. Lindle, Dale L. Perry

Separations Campaign (TRP)

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF₄, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Organic Matrix, Spencer M. Steinberg

Separations Campaign (TRP)

The recovery of iodine released during the processing of used nuclear fuel poses a significant challenge to the transmutation of radioactive iodine. This proposal will develop and examine the use of Fullerene Containing Carbon (FCC) compounds as potential sorbents for iodine release from the reprocessing of nuclear fuel. This work will also include the development of bench-scale testing capabilities at UNLV to allow the testing of the FCC material in a simulated process off-gas environment. This experimental capability will also be used to test other potential sorbtion materials and processes, such as natural organic matter (NOM) and other promising alternatives. …

Computational Simulation Of The Docking Of Prochlorothrix Hollandica Plastocyanin To Photosystem I: Modeling The Electron Transfer Complex, Neocles B. Leontis, Eugene Myshkin, George S. Bullerjahn

Chemistry Faculty Publications

We have used several docking algorithms (GRAMM, FTDOCK, DOT, AUTODOCK) to examine protein-protein interactions between plastocyanin (Pc)/photosystem I (PSI) in the electron transfer reaction. Because of the large size and complexity of this system, it is faster and easier to use computer simulations than conduct x-ray crystallography or nuclear magnetic resonance experiments. The main criterion for complex selection was the distance between the copper ion of Pc and the P700 chlorophyll special pair. Additionally, the unique tyrosine residue (Tyr(12)) of the hydrophobic docking surface of Prochlorothrix hollandica Pc yields a specific interaction with the lumenal surface of PSI, thus providing …

Organic Geochemical Analysis Of Late-Glacial And Early-Holocene Ecosystem Changes: A Case Study From Northern New England Lakes, Michael A. Kruge, Andrea Lini

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

The lacustrine sedimentary archive of organic remains provides important evidence for the reconstruction of the environmental histories of lakes and their watersheds, recording the response of the Earth's biota to changes on scales varying from the local to the global. The last Glacial-Interglacial transition presents an opportunity to investigate how, and at what rates, watershed and lake ecosystems were established on once glaciated, carbon and nutrient-poor landscapes. The small lakes of northern Vermont (USA) provide an appropriate setting in which to investigate such changes.

As part of a multidisciplinary study of three Vermont lake sediment cores, samples ranging in age …

Luminescence Lifetime-Based Sensor For Cyanide And Related Anions, Pavel Anzenbacher Jr., Daniel S. Tyson, Karolina Jursı´Kova, Felix N. Castellano

Chemistry Faculty Publications

A new Ru(II) complex is described which serves as a luminescence lifetime-based sensor for fluoride and cyanide anions (KF = 640 000 mol-1, KCN = 430 000 mol-1). This chromophore displays observable changes in its UV-vis and steady-state luminescence spectra upon cyanide binding. Prior to cyanide addition, this complex exhibits a single-exponential lifetime (tau = 377 +/- 20 ns). With increasing cyanide concentrations, the intensity decays are composed of two exponentials: long tau (320-370 ns) and short tau (13-17 ns). The average lifetimes shorten as a function of cyanide concentration since the fractional intensity shifts from an initial dominant long …

Synthesis Of Cyclopropanes Via Organoiron Methodology: Stereoselective Preparation Of Cis-2-(2’-Carboxycyclopropyl)Glycine, Nathaniel J Wallock, William A. Donaldson

Chemistry Faculty Research and Publications

A stereoselective route to cis-2-(2′-carboxycyclopropyl)glycine has been developed. exo-Nucleophilic addition to the (bicyclo[5.1.0]octadienyl)iron(1+) cation establishes the relative stereochemistry at the cyclopropane ring and the α-stereocenter. Subsequent removal of the metal and cleavage of the cyclic diene gave the protected target 10, which upon hydrolysis gave 1.

A stereoselective route to cis-2-(2′-carboxycyclopropyl)glycine has been developed. exo-Nucleophilic addition to the (bicyclo[5.1.0]octadienyl)iron(1+) cation establishes the relative stereochemistry at the cyclopropane ring and the α-stereocenter.

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics-Phase Two, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The proposed work will combine chemical kinetics and hydrodynamics in target and test-loop lead-bismuth eutectic (LBE) systems to model system corrosion effects. This approach will result in a predicative tool that can be validated with corrosion test data, used to systematically design tests and interpret the results, and provide guidance for optimization in LBE system designs. The task includes two subtasks. The first subtask is to try to develop the necessary predictive tools to be able to predict the levels of oxygen and corrosion products close to the boundary layer through the use of Computational Fluid Dynamics (CFD) modeling. The …

Development Of A Systems Engineering Model Of The Chemical Separations Process, Yitung Chen, Darrell Pepper, Randy Clarksean

Separations Campaign (TRP)

Two activities are proposed: the development of a systems engineering model and the refinement of the Argonne code AMUSE (Argonne Model for Universal Solvent Extraction). The detailed systems engineering model will be the start of an integrated approach to the analysis of the materials separations associated with the AAA Program. A second portion of the project will streamline and improve an integral part of the overall systems model, which is the software package AMUSE. AMUSE analyzes the UREX process and other related solvent extraction processes and defines many of the process streams that are integral to the systems engineering model. …

Novel Synthesis Of 2-Methyl-3, 4, 5-Trichloropyrimidine, Daniel M. Goldman

Theses

A one-step synthesis of the heterocycle 2-methyl-3,4,5-trichloropyrimidine by the cycloaddition of hexachloropropene with acetamidine hydrochloride in methanolic NaOH was attempted. The product was dark amber oil. A by-product of this reaction was sodium chloride. The proposed reaction was expected to proceed via a SN2 nucleophilic displacement of three chlorine atoms on hexachloropropene by acetamidine, the nucleophile. The proposed driving force for this transformation is the lone pair of electrons on the amidine nitrogen along with the electron withdrawing ability of three chlorines on hexachloropropene which induces a partial positive charge on the carbon. It is proposed that the chlorine atoms …

The Electrochemical Etching Of Metals, Li-Min Jiang, Zhong-Qun Tian, Zhu-Fang Liu, Bin-Wei Mao, Hai-Gou Huang, Jian-Jun Sun

Journal of Electrochemistry

All kinds of current methods for etching metals are reviewed. The electrochemical etching methods among them, including through-mask, scanning electrochemical microscopy, confined etchant layer technique, electrochemical scanning tunneling microscopy and super-short potential pulse, are discussed in detail. The compositive analyses were made for the methods in terms of the processing precision (whether processing in micrometer or nanometer scale), the processing efficiency (the complexity of the procedure, and whether fabricating in batch), the extent of application (mainly refer to the procedure, and whether fabricating in batch), the extent of results was shown that each method has itself advantage and imperfection. The …

The Preparation And Characterization Of Growing Preferentially Cds Nanopartile Film, Huai-Guo Huang, Yan-Yan Xi, Zhi-Xin Zheng, Jia-Wei Yan, Jian-Zhang Zhou, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

CdS nanoparticle films were prepared on the PANI film, PATP film, Au film and ITO respectively by constant current deposition or current impulse method, and their structure and character were also studied. The results show that the substrates influence the structure and character of CdS particle film.

An Investigation On Sr-Doped Spinel Phase-LisrXMn2-XO4, Hui Zhan, Yun-Hong Zhou

Journal of Electrochemistry

Sr-doped spinel phase-LiSr_xMn_2-xO₄ was successfully prepared by solid-state method. Structural and electrochemical characterizations were carried out. Although Sr²⁺ has a large ion radius-1.12 , the spinel structure can be well maintained for LiSr_xMn_2-xO₄ sample as far as the x value doesn't surpass 0.05. Electrochemical study presents supporting evidence that doping the stoichiometric LiSr_xMn_2-xO₄ phase with Sr is an effective way to improve the cycleability of LiSr_xMn_2-xO₄ spinel material. A remarkable enhancement of the cycleability with retention of the initial …

Polishing Rate And Dependent Factors Of Copper In Nh3 ·H2O Aqueous Solution Containing K3Fe(Cn)6 During Cmp, Han-Wei He, Yue-Hua Hu, Ke-Long Huang

Journal of Electrochemistry

Dependence of polishing rates of copper on concentrations of NH₃·H₂O, passivator K₃[Fe(CN)₆], γ-Al₂O₃ abrasives and polishing pressures, polishing rotative rates were studied. Dependent mechanisms were explained. It was shown a linear relation between polishing and polishing pressures and rotative rates within some range, non-linear relation between polishing and various reagent concentrations. Preston coefficient was varied. CMP recipe of the best polishing rate was gained: 4%K₃Fe(CN)₆+1%NH₃·H₂O+25%γ-Al₂O₃, K_p=0.02383. Technics conditions were 300 rpm and 80 kpa. The …

Electrosynthesis Of Glyoxylic Acid In A Cooled Cathode Reactor, Jin-Hong Fan, Jun Li, Xue-Yun Chen, Wei Li, Hao-Qi Gao

Journal of Electrochemistry

Glyoxylic acid was produced by electroreduction of oxalic acid in a well designed cooled cathode reactor. The cathodic and anodic electrolytes were super-saturated oxalic acid and hydrochloric acid aqueous solutions separated by a super-acid ion-exchange membrane. The current efficiency and time-space yield of glyoxylic acid were studied under different temperatures of cathode and electrolyte, current densities, materials of cathode. With the cooled cathode reactor, the energy consumption was reduced and higher oxalic acid concentration was available in solution, so that current efficiency was improved. The results indicated that the average time-space yield of glyoxylic acid was about 0.032 kg·dm^{-3 …}

Self-Assembled Monolayer Of Schiff Bases On Au Electrode, Ke-Qiang Ding, Qing-Fei Wang, Zhen-Bin Jia, Na Tian, Ning Wang, Ru-Ting Tong, Xin-Kui Wang, Hui-Bo Shao

Journal of Electrochemistry

Schiff bases tailored with -SH group, was self-assembled on Au substrate for the first time. The packing degree of this monolayer was described with SEM technique. Spontaneously, the self-assembled monolayer (SAM) was briefly characterized with CV and EIS methods. Though Comparing with the SAM of alkanethiol, the membrane we fabricated was relatively loose, our work is the first step to study Schiff bases by means of self-assembled monolayer.

Application Of Electrochemical Techniques To The Researches In Life Science, Jian-Tao Pang, Chun-Hai Fan, Gen-Xi Li

Journal of Electrochemistry

The research work of our group in the last two years is briefly reviewed in this paper. By using electrochemical method, and combining some other chemical and biological techniques, lots of achievements have been obtained. And these researches are towards some hot topics in life science, such as function conversion, interaction between signal molecules and proteins, electron-transfer of biomolecules, gene detection, structural biology, biochemical analysis and the third generation biosensors.

Development Of 200～500 W Portable Proton Exchange Membrane Fuel Cell Power System, Li-Qing Hu, Li-Rong Zhou, Zheng Li, Jian-Wei Xia, Ming-Zhu Fu, Xin Wu, Yun Zhu

Journal of Electrochemistry

The Properties of the Portable PEM Fuel Cell Power Source are very unique compared with the common primary or rechargeable electro-chemical battery. This paper describes the In this work, of the 200～500 W portable PEM fuel cell power system, was developed. The system mainly composed of four subsystem: 1)Fuel cell stack; 2)Air delivery; 3)Hydrogen source; 4)Heat dissipation and system control.

Corrosive Electrochemical Behavior Of Carbon Steel In Microbiological Medium, Jing Liu, Hong-Bo Fan, Hai-Ping Xu, Jia-Shen Zheng, Li-Ming Xu, Zong-Qiang Mao

Journal of Electrochemistry

Sulfate-reducing bacteria (SRB)grows and propagates, PH of the solution is dropped from 7.5 to 5.8, and forms the biofilms on carbon steel in culture medium. The micro-environment on the surface of carbon steel is changed under the biofilms, the factors accelerate the formation of the pitting corrosion. When the biofilm on carbon steel is cleaned out, the surface of carbon steel have the non-uniform pitting corrosion. The activity of SRB and the porous structure of biofilms induced the initiation and development of the pitting corrosion of carbon steel. The process of microbiologically induced corrosion (MIC) involves the development of SRB …