Chemistry Commons^™

Coherence Peak And Superconducting Energy Gap In Rb_{3}C_{60} Observed By Muon Spin Relaxation, R. F. Kiefl, W. A. Macfarlane, K. H. Chow, S. Dunsiger, T. L. Duty, T. M. S. Johnston, J. W. Schneider, J. Sonier, Laurent Brard, Robert M. Strongin, J. E. Fischer, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

Muon spin relaxation resulting from spin exchange scattering of endohedral muonium (μ+e-) with thermal electronic excitations has been observed in the fullerene superconductor Rb₃C₆₀. The temperature dependence of T₁^-1 shows a coherence peak just below T_c and can be fit to the conventional Hebel-Slichter theory for spin relaxation in a superconductor with a broadened BCS density of states. The average energy gap for electronic excitations, Δ/k_B=53(4) K or 2Δ/ k_BT_c=3.6(3), is consistent with the BCS weak coupling limit.

Unusual Thermal Stability Of A Site-Ordered Mc60 Rocksalt Structure (M=K, Rb, Or Cs), Q. Zhu, O. Zhou, J. E. Fischer, Andrew R. Mcghie, W. R. Romanow, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

X-ray diffraction and differential scanning calorimetry of M_xC₆₀, with x∼1 and M=K, Rb, or Cs, reveal an unusual T-dependent phase sequence. A low-symmetry ground state is found, while the high-T limit is an ordered rocksalt structure in which only the octahedral sites are occupied. The unusual high-T stability of this ordered phase is attributed to the entropy of molecular orientational disorder and/or thermal disorder of the alkali-metal ions within the octahedral sites. Unique to K_xC₆₀ with x≥1.4, we find at intermediate temperatures an fcc site-disordered lattice gas …

Nuclear Magnetic Resonance Study Of Antigen-Antibody Complexes, Including Sequence Specific Assignments And Structural Analysis Of Neurophysin As An Antigen Model, Elisar Jamil Barbar

Dissertations and Theses

The interaction between molecules is essential in a wide range of biological processes. A detailed knowledge of these interactions is necessary for understanding these processes. Among the systems that involve important interactions is the immune system. NMR spectroscopy has a large number of spectral parameters that were used in this work to study antibody-antigen interactions. These same parameters were also used to begin a structural analysis of a medium-sized protein, neurophysin, that has important interactions with neurohormones, and served here as a model antigen. A set of ligands differing in size and charge was designed and used to probe the …

Dynamic Nmr Study Of Bond Rotational Activation Parameters In Micelles, Dietmar A. Leitner

Dissertations and Theses

The behavior of surfactants in solution has been and still is of scientific, technological, and industrial interest. The micelle forming compounds sodium N-( octyloxycarbonyl)sarcosinate (NaOcSarc), and sodium N-(decyloxycarbonyl)sarcosinate (NaDecSarc) show in aqueous solution two ¹H NMR N-methyl peaks arising from a possible cis- or trans-conformation. The relative population of the N-methyl peaks depends mostly on the concentration of surfactant indicating micelle formation. Upon heating the two peaks start to coalesce and finally appear as one single peak. The temperature range in which this phenomenon occurs is from 25°C to 65°C. The primary interest of this study was to determine …

Theoretical And Experimental Evaluation Of Hysteresis In Atmospheric Chemistry, Theodore Alan Haigh

Dissertations and Theses

This treatise is a recapitulation of the theoretical and experimental study of hysteresis in atmospheric kinetics. The original problem arose from a theoretical study of a series of reactions for clean air. Upon evaluation a bistable equilibrium was predicted. The steady-state analysis had delineated a metastable region for the set of reactions. This bounded region is the hysteresis that this research project evaluated.

The Synthesis And Chemistry Of N-Chlorosulfenylaziridines, Michael Claude Hare

Dissertations and Theses

Thiazyl chloride, the monomer of trichlorotrithiazene, reacts with fluorinated olefins to form N-chlorosulfenylaziridines. Four members of this new class of compounds have been prepared. Fluorine NMR, carbon-13 NMR, mass spectrometry, infrared spectroscopy, and elemental analysis have been used to characterize these compounds.

Preparation Of Electron Donor And Acceptor Molecules For Porphyrin Derivatization, Christoph Hoefler

Dissertations and Theses

Porphyrins derivatized with electron donating and electron withdrawing groups can be used for artificial photosynthesis. Four new compounds, two electron donors and two electron acceptors, have been synthesized for prospective porphyrin linkages.

Bis(1h+-Pyrazinium N4-Oxide) Dichromate, Gary L. Gard, Roger D. Willett, W. W. Paudler, R. M. Sheets, Mark R. Pressprich

Chemistry Faculty Publications and Presentations

2C₄H₅N₂O⁺.Cr₂O²₇⁻, Mᵣ=410∙2, monoclinic, P2₁, a=8∙(2), b=6∙132 (2), c=14∙493 (4) Å, β=94∙50 (2)°, V=708∙8 (3) ų, Z=2, Dₓ=1∙92 g cm⁻³, Mο Κα, λ=0∙71069 Å, μ=15∙5 cm⁻¹, F(000)=412, T=293 K, R=0∙0602 for 1980 unique observed reflections with F≥3σ(F). The structure consists of discrete dinegative dichromate anions hydrogen bonded to monopositive pyrazinium N-oxide cations (N―H∙∙∙O=2∙724, 2∙644 Å). A strong hydrogen bond to the bridging O atom in the Cr₂O²₇⁻ anion leads to significant lengthening of the bridging Cr―O bonds. A short C―H∙∙∙O interaction (3∙180 Å) is also observed.

An Analysis Of The Inhibitory Effects Of Linolenic Acid Upon Photosystem Ii Of Higher Plants, Mark Edward Iven

Dissertations and Theses

This study utilizes steady state fluorescence measurements, flash-induced P680+ absorption transients, and DCIP reduction kinetics to study the inhibitory effects of linolenic acid (LA) upon Photosystem II (PSII) in whole spinach chloroplasts and insideout wheat thylakoids. It confirms the presence within PSII of LA-induced inhibition of energy trapping and/or primary charge separation (i.e., primary inhibition), in addition to donor side inhibition. The latter is diminished in the presence of 1,5-Diphenylcarbohydrazide (DPC) and probably takes place at the oxygen evolving complex. Primary inhibition, which is more controversial, probably occurs between Ph and QA, with a likely contribution at the level of …

Study Of Photolytic Interference On Ho Measurements By Lif-Fage, Carmen Ivette Martinez

Dissertations and Theses

For many years there has been a great interest among the scientific community in the study of the hydroxyl radical, HO. This interest stems from the fundamental role played by this molecule in the photochemistry of the atmosphere, mainly as a cleansing agent of environmental pollutants. Knowing the concentration of the radical would enable scientists to corroborate current atmospheric models and to predict future trends in the atmosphere. Even though there is a great interest in the determination of atmospheric concentrations of this molecule, the task has been very difficult. This is mainly due to the lack of a method …

Fluorinated Esters: Synthesis And Identification, Jilla Schaff

Dissertations and Theses

Reactions of different alcohols with 2-hydroxy - 1- trifluoromethyl -1,2,2-trifluoroethanesulfonic acid sultone F₃CCFCF₂OSO₂ were studied. Six new esters were prepared: C₆F₅OC(O)CF(CF₃)SO₂F, CH₃CH₂OC(O)CF(CF₃)SO₂F, CF₃CH₂OC(O)CF(CF₃)SO₂F, (CF₃)₂CHOC(O)CF(CF₃)SO₂F, CH2=CHCH₂OC(O)CF(CF₃)SO₂F, (CH₂OC(O)CF(CF₃)SO₂F)₂. Analytical data, infrared, nmr and mass spectra are presented supporting the proposed structures for these new compounds.

Fluorinated [Beta]-Sultones As Precursors To Fluorinated Sulfonic Acids, And New Fluorosulfonyl Containing Monomers/Polymers, Javid Mohtasham

Dissertations and Theses

Sulfur trioxide (SO₃) adds to fluoroolefins of the form RCF=CF₂, (where R = F, SF₅, CF₃, CF₃OCF₂, CF₂=CF(CF₂)₂, CF₃(CF₂)₃O, CF₃O(CF₂)₂OCF₂, or CH₂ClCHClCH₂), yielding the fluorinated [beta]-sultones, RCFCF₂OSO₂. In the case of CF₃(CF₂)₃OCF=CF₂, a reverse addition occurs, giving the sultone, CF₃(CF₂)₃CF₂2OCFCF₂SO₂O. The fluoro [beta]-sultones are capable of undergoing different reactions, such as rearrangement, hydrolysis, esterification, and polymerization. These reactions, will result in the formation of compounds containing the fluorosulfonyl grouping (SO₂F); it is this group that yields the corresponding sulfonic acid upon base/acid treatment.

The addition of sodium bisulfite to CF₃CF= CF₂ and CF₃(CF₂)₄CF=CF₂ in the presence of (C₆H₅CO)₂O₂ and Na₂B₄O₇·10H₂O …

The Chemistry Of Sulfonyl Fluorides: Sf5 And/Or So2f Containing Compounds As Precursors To Sulfonic Acids, Robin Joyce Terjeson

Dissertations and Theses

Sulfonyl fluoride systems and their derivatives, RS0₂F, where R represents hydrocarbon/fluorocarbon moieties continue to be of considerable interest. The incorporation of the sulfonyl fluoride group (S0₂F) into molecular systems can lead to compounds that are useful as ion-exchange resins, surface active agents, fuel cell electrolytes, and strong sulfonic acids/salts.

Interest in preparing SF₅ containing sulfonyl fluorides led to the synthesis of the ᵝ-sultone, SF₅CHCF₂0S0₂, and its rearranged product. Hydrolysis of the sultone gave SF₅CH₂S0₂F which led to the sulfonic acid and salt, SF …

Chemical Modification Of Skeletal Muscle Sarcoplasmic Reticulum Vesicles: A Study Of Calcium Permeability, Janice F. Stuart

Dissertations and Theses

Skeletal muscle contains an internal membrane system called the sarcoplasmic reticulum (SR) whose function is to regulate the Ca²⁺ concentration of the myoplasm. Ca²⁺ is transported into the SR from the myoplasm via a Ca²⁺ dependent ATPase thus lowering the myoplasmic Ca²⁺ concentration. Ca²⁺ exits from the SR via a Ca²⁺ releqse pathway resultingin the increase of myoplasmic Ca²⁺. Muscles contract when the myoplasmic Ca²⁺ concentration is > 5 uM and relax when the Ca²⁺ concentration is lowered below 1 uM. The Ca²⁺ dependent ATPase has been extensively studied but …

Analysis Of Ferredoxin And Flavodoxin In Anabaena And Trichodesmium Using Fast Protein Liquid Chromatography, Karen Lorraine Jones

Dissertations and Theses

Iron is an essential nutrient for growth of photosynthetic microorganisms such as cyanobacteria and algae. Iron is required for proteins involved in the important processes of carbon and nitrogen assimilation. Low concentrations of iron in cultures or natural waters can lead to iron limitation which affects many aspects of algal metabolism. In natural waters, iron limitation can have effects on the patterns and rates of primary productivity.

The cellular content of certain proteins can be affected by media iron concentrations. Methods have been used that assay components of the cell as an indirect measure of iron nutritional status. For example, …

Medium Resolution Atmospheric Pressure Ionization Mass Spectrometer, Andrew H. Grange, Robert J. O'Brien, Douglas F. Barofsky

Chemistry Faculty Publications and Presentations

An atmospheric pressure ionization (API) source for a VG 7070E‐HF mass spectrometer has been built and successfully operated at an accelerating potential of 6 kV. Hydrated protons and hydrated organic ions formed in the API source can be either partially or completely disaggregated by collisionally induced dissociation before entering the mass analyzer. The protonated molecular ions of pinacolone and 2,4‐pentanedione can be fully separated (R=2800, m/z 101,

Synthesis And Characterization Of Some Sf₅- Containing Sulfonic Acids, Robert J. Willenbring

Dissertations and Theses

Pentafluorosulfur (VI) bromide (SF₅Br) adds to olefins of the form CX₂=CX₂, where X= H or F, with the pentafluorosulfur group usually adding to the carbon with more hydrogens attached to it. This series of compounds was used in an attempt to prepare the corresponding sulfonic acid hydrates of the general formula SF₅CX₂CX₂SO₃H·nH₂O, in order to have these compounds tested as possible fuel cell electrolytes. The reaction scheme involved reflux of the SF₅Br adduct with an equimolar amount of sodium sulfite in 50% …

The Chemistry Of Novel Chromium(Iv) Systems And Fluorinated Hypochlorites, Joseph Onuorah Udeaja

Dissertations and Theses

Chromium(IV) has been of interest for some time because of its role as an intermediate in chromic oxidation reactions. Since there are not a great number of stable tetravalent chromium complexes known, and the use of such species as oxidizing agents has not been widely explored, the preparation, isolation and characterization of new stable tetravalent chromium species may allow chemists the opportunity to more fully understand the role which tetravalent chromium plays in oxidation reactions. The present study thus involves the synthesis of Cr(OC₄H₉)₄ and other Cr(IV) derivatives and the use of Cr(OC₄H …

Derivatives Of Trifluorovinylsulfur Pentafluoride And F-(Tert-Butyl) Hypochlorite, Jo Ann Marie Canich

Dissertations and Theses

Trifluorovinylsulfur pentafluoride dimerizes to (SF₅CFCF₂)₂ in the presence of cesium fluoride. Two derivatives of trifluorovinylsulfur pentafluoride, SF₅CF(CF₃)C(O)F and SF₅CF(CF₃)C(O)NH₂, were used to prepare the new compounds, SF₅CF(CF₃)CO₂H and SF₅CF(CF₃)CN, respectively. The first was prepared by reacting the SF₅-acid fluoride with water, while the second involved the abstraction of water from the SF₅-amide using P₄O₁₀. The attempted preparation of a bis-pentafluorosulfur ketone and a pentafluorosulfur containing acid anhydride …

High Valent Chromium (V) And Chromium (Vi) Complexes, Harry Bennett Davis

Dissertations and Theses

A new preparative route to the only neutral chromium(V) oxide fluoride, chromium oxide trifluoride, has been accomplished by the reaction of xenon difluoride with chromyl fluoride at high temperature. The chromium oxide trifluoride is produced as crystals which are suitable for single crystal studies. In reactions of chromium oxide trifluoride with alkali and alkaline metal fluorides in anhydrous hydrogen fluoride, new chromium(V) oxide fluoride salts were obtained; these salts were not of high purity due to unknown problems. An attempt to prepare chromium oxide tetrafluoride by the reaction of xenon difluoride with chromyl fluoride in anhydrous hydrogen fluoride failed to …

Measurement Of Low Vapor Pressures : A Kinetic Approach, Samuel Bernard Bliden

Dissertations and Theses

A kinetic model was applied to vapor pressure data obtained by a variable flow method. The vapor pressures of benzoic acid, naphthalene, benzophenone, and phenylhydrazine were measured at temperatures of 293K to 307K. The data are summarized in the data table on the following page. These data were obtained by passing air over a sample of the substance in a tube. The air stream was combusted, and a flame ionization detector was used to measure the mass of CO₂ so obtained. Several different flow rates were used at each temperature with each substance.

A Theoretical And Experimental Examination Of Sodium Chloride Hydration, Debra Conway Modra

Dissertations and Theses

A Hitachi Hu 125C transmission electron microscope in which the standard specimen holder was replaced by an environmental cell was used to observe the hydration of sodium chloride crystals. To observe Kelvin curvature and solubility effects sodium chloride crystals which were 0.1u or smaller were of special interest. An electrohome video system attached to the electron microscope was used to record the sodium chloride hydration for subsequent particle measurement and viewing.

A theoretical model was also developed. Thermodynamic properties such as the Kelvin curvature and solubility effects were considered as well as the kinetic expressions for salt dissolution/recrystalization and water …

Generalized Response Of Chemiluminescence Analyzers, A. A. Mehrabzadeh, Robert J. O'Brien, Thomas M. Hard

Chemistry Faculty Publications and Presentations

The mass flow and chemical kinetic equations for a gaseous chemiluminescence (CL) analyzer are formulated and solved. The resultant equation can be used to predict the absolute response of the analyzer as a function of the sample flow rate, the sample gas pressure, the chamber pressure, the chamber volume, the mass flow rate and mole fraction of the reagent gas, and the rate constants of the relevant chemical processes. Thus, the equation allows optimization of these parameters. It is shown that for varying sample pressure the analyzer can be used to measure either concentration or mole fraction and that interfering …

The Combined Effect Of Cu And Zn On Selenastrum Capricornutum, Helmer Colonia-Roque

Dissertations and Theses

It has been demonstrated that the toxicity of heavy metals depends on their chemical speciation and can be related to their free ion activities, rather than the total metal concentrations. The objective of this study was to determine the effect of combined free ions of zinc and copper on the toxicity to the green alga Selenastrum capricornutum. This alga was grown in a defined medium, under controlled laboratory conditions, with a varying range of zinc and copper concentrations. The growth rate of the alga was inhibited at pZn = 5.93 or at pCu = 7.24. The results suggest that …

The Effects Of Various Chemical Treatments On The Surface Area Of Coals, Maria Margaret Ludvig

Dissertations and Theses

Surface areas of most American coals are small when measured by N₂ adsorption at 77 K and large when measured by CO₂ adsorption at 298 K, implying that the majority of the pores are less than 5 Å in diameter. This small pore size would restrict many gaseous and liquid reactants from entering the internal pore system of the coal, and hence, reduces the efficiency of coal conversion. Therefore, if the surface area, as measured by N₂ (77 K), could be increased, that is, to increase the pore size, the conversion of coal into useful products should …

An Investigation Of Cadmium And Sulfur Reactions In Dimethylsulfoxide, Howard W. Hogle

Dissertations and Theses

The study of the reaction of cadmium and sulfur in dimethylsulfoxide (DMSO) is presented. Specifically, the reaction of dissolved molecular sulfur in DMSO at temperatures greater than 90°C with freshly precipitated metallic cadmium is followed by UV-visible spectrometry, atomic absorption spectrometry, and Raman spectrometry. Evidence for the formation of a new cadmium-sulfur species and S₃^- is discussed. In a second reaction, an equilibrium sodium polysulfide solution in DMSO is titrated with a solution of cadmium ion at room temperature and the reaction progress is followed by means of UV-visible spectrometry. A calculation of the average number of polysulfide …

Hydroxide Binding Equilibrium In Hemerythrin, John David Mccallum

Dissertations and Theses

The measurement of the equilibrium constant and the thermodynamic parameters of the binding of hydroxide ions to the active site of hemerythrin, an invertebrate iron containing protein, was done by a new difference spectroscopic method. The method enables accurate measurements of equilibrium constants without accurate knowledge of molar absorptivities or protein concentrations and is novel in that it takes the difference between the two equilibrium mixtures, thus enabling the measurement of equilibrium constants when it is not convenient or possible to produce either substance as a pure reference material.

Chemistry Of Chromium Oxyfluorides And Group Vib Perfluoroglutarates, Bruce Michael Johnson

Dissertations and Theses

Pure chromium oxide trifluoride was prepared for the first time by reaction of CrO₃ and ClF with subsequent multiple fluorine treatments at 120°C. On the basis of its infrared spectrum, the purple CrOF₃ was assigned as a fluorine-bridged polymer with terminal oxygen groups. Chromium oxide trifluoride was found to be stable to 300°C, where it decomposes with the loss of oxygen to CrF₃.

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.

Pressure Dependence Of Fluorescent And Photolytic Interferences In Ho Detection By Laser-Excited Fluorescence, Thomas M. Hard, Robert J. O'Brien, T. B. Cook

Chemistry Faculty Publications and Presentations

In the measurement of HO concentrations by laser-excited fluorescence, expansion of the sampled air offers a way to reduce fluorescent and photolytic interference by other species. The decrease in [HO] upon expansion is balanced by an increase in HO fluorescence yield over a wide range of pressures. Background air fluorescence is reduced if the responsible species have fluorescence yields higher than those of HO. Preliminary experiments indicate that most of the fluorescence observed in laboratory air is due to such species. Upon expansion, the suppression of fluorescent interference can be no greater than the reduction in pressure, whereas the suppression …