Chemistry Commons^™

Flame Retardancy Of Polymer Nanocomposites Based On Layered Aluminum Phosphate And Computational Study Of Intercalation Of Amines Into Α-Zirconium Phosphate And Adsorption Of A Model Organic Pollutant, Ning Wang 1982-

Master's Theses (2009 -)

Layered metal materials, such as layered metal hydroxides, hydroxy double salts, and layered metal phosphates can be used for applications such as fire retardancy, ion exchangers, or removal of pollutants. Optimization of materials for these applications requires an understanding of their physical and chemical properties.

Part A: Flame retardancy of polymer nanocomposites based on taranakite

Taranakite with tunable interlayer spacing has been prepared and modified by sodium dodecyl sulfate (AL-SDS). The layered materials are used as the additive to study the fire retardancy of polymers, including polystyrene (PS), polypropylene (PP), and polyvinyl alcohol (PVA). The dispersion of taranakite was characterized …

Fluorescence Probes For Cellular Thiol And Disulfide Detection: Sythesis And Biophysical Characterization, Timothy Jonhera

Dissertations (1934 -)

The total concentration of cellular thiols is about 30 mM, and use of current fluorescent chemical probes to quantitate these thiols inside cells is impractical. We recently reported fluorescent dithio probes (donor-S-S-acceptor, DSSA) with unusually low reduction potential (- 0.6 V) that can detect changes in intracellular thiols and cross membranes of bacterial and mammalian cells, but they could not quantify thiol redox state. Here we report a new variant of the DSSA series, which has hydroxy coumarin (Ex: 320 nm, Em: 460 nm) as donor and fluorescein (Ex: 485 nm, Em: 520 nm) as acceptor. The probe was characterized …

Development, Kinetic Analysis And Applications Of 2-D Nanostructured Layered Metal Hydroxides, Stephen Majoni

Dissertations (1934 -)

Nanodimensional layered metal hydroxides which include layered hydroxy salts (LHSs) and hydroxy double salts (HDSs) have the ability to accommodate species between the layers. The structural composition of these materials can be tuned so as to create materials with targeted physico-chemical properties for applications where it is advantageous to intercalate or release molecules. Some of the applications include ion-exchange, fire retardation, catalysis, and controlled release delivery. Anion exchange reactions are among methods used to optimize these materials for targeted applications, making the characterization of exchange kinetics of practical interest. In addition, understanding fundamental factors that control retention and release of …

Complete Determination Of The Pin1 Catalytic Domain Thermodynamic Cycle By Nmr Lineshape Analysis, Alexander I. Greenwood, Monique J. Rogals, Soumya De, Kun Ping Lu, Evgenii L. Kovrigin, Linda K. Nicholson

Chemistry Faculty Research and Publications

The phosphorylation-specific peptidyl-prolyl isomerase Pin1 catalyzes the isomerization of the peptide bond preceding a proline residue between cis and trans isomers. To best understand the mechanisms of Pin1 regulation, rigorous enzymatic assays of isomerization are required. However, most measures of isomerase activity require significant constraints on substrate sequence and only yield rate constants for the cis isomer, k^cis_catand apparent Michaelis constants, K^App_M . By contrast, NMR lineshape analysis is a powerful tool for determining microscopic rates and populations of each state in a complex binding scheme. The isolated catalytic domain of Pin1 was employed as …

Synthetic And Mechanistic Studies Of Coupling Reactions Involving C-H Bond Activation, Ki Hyeok Kwon

Dissertations (1934 -)

Transition metal-catalyzed C-C bond forming reactions involving C-H bond activation have been shown to be effective methods for functionalization of unreactive compounds. Since Murai's pioneering work on ruthenium-catalyzed regioselective arene-to-alkene coupling reactions, a number of well-defined, late transition metal catalysts have been shown to mediate regioseletive C-C bond forming reaction involving C-H bond activation. Recently, late transition metal complexes have also been found to catalyze the regioselective coupling reaction of nitrogen containing compounds with alkenes as well as sp3 bond insertions and oxidative coupling reaction of aimdes. The catalytic C-C bond forming reaction involving C-H bond activation would provide simple …

Generation Of Diverse Molecular Complexity From Simple Hydrocarbons, Anobick Sar

Dissertations (1934 -)

In an effort to make diverse molecular complexity from simple hydrocarbons, tricarbonyl(cyclohexadienyl)iron(+1) cation was prepared in two steps from 1, 3-cycloxehadiene. Reactivity of the symmetric iron cation with heteroatom nucleophiles and stabilized carbon nucleophiles was studied. Nucleophilic attack of potassium phthalimide at the dienyl terminus of the cation followed by oxidative decomplexation with Ce4+ provided the ligand N-(2,4-cyclohexadiene-1-yl)phthalimide. A series of stereochemically diverse polyhydroxyl aminocyclohexane "aminocyclitols" derivatives and a number of racemic and optically active hydroxy-and polyhydroxy 1,3-diaminocyclohexane derivatives have been synthesized from N-(2,4-cyclohexadiene-1-yl)phthalimide. The relative stereochemistries of the compounds ware assigned on the basis of the 1H NMR data …

Design, Synthesis And Studies Directed Towards The Photophysical Properties Of The Polycyclic Aromatic Hydrocarbons, Rekha Sharma

Master's Theses (2009 -)

The cross conjugated molecules are also known as cruciforms, which effectively allow the HOMO-LUMO separation. The term Cruciform is used for diaxial chromophores in which the properties of the two axes can be manipulated upon suitable substitution with auxochromic substituents. Originally designed for molecular electronic applications, the discovery that these cruciforms possess a platform where Frontier Molecular Orbitals can be tuned, led to their investigative research as sensory flourophores. In the majority of organic chromophores, the HOMO and the LUMO are congruent. Thus, upon binding to an analyte both HOMO and LUMO are almost equally affected and hence large shifts …

Binding Energy Predictions Of Positron- And Positronium-Atom System, Xiang Cheng

Master's Theses (2009 -)

There has been a large amount of work studying positron and positronium (Ps) binding to atoms. Twelve atoms (including Ps) are known to bind with a positron and 14 atoms won't. For Ps binding, 12 atoms are found to bind with Ps and 2 atoms do not. For both positron and Ps binding to atoms, we find that the known binding energy can be fitted to a simple expression involving several common physical properties. Positron binding energies can be fitted using the parameters of ionization potentials, polarizabilities, and the number of s electrons of the atoms; while Ps binding energies …

Development And Applications Of Ionic Liquids And Near-Infrared Multispectral Imaging Techniques, Irena Mejac

Dissertations (1934 -)

In this work, we explore novel analytical applications of Ionic Liquids and Near-infrared multispectral imaging microscopy.

Ionic liquids (ILs) belong to a group of organic salts that are liquid at room temperature and can be, due to their unique chemical and physical properties, successfully used for a variety of applications. The main goal of this study was to explore the synergistic use of ILs in chemical separations. Specifically, chiral ILs were used as novel chiral selectors for Capillary Electrophoresis and as solvents for stationary phase in Gas Chromatography. As chiral selectors IL provides baseline-separation as well as enantiomeric separation of …

Spectroelectrochemistry And Voltammetry Of Metalloporphinones, Florentina Tutunea

Dissertations (1934 -)

Metalloporphinones have been found in a number of enzymes involved in nitrogen metabolism. The emphasis of this research project has been to develop spectroscopic markers in order to identify metal versus porphinone reduction. The carbonyl group in the porphinone has a very strong signal which is quite sensitive to the extent of reduction of the porphinone macrocycle.

The spectral change makes IR an important tool in the process of structure determination of metalloporphyrins because the carbonyl group shift can be correlated with the metal oxidation state. It was observed from previously published studies that a higher metal oxidation state moves …

An In Vitro Spectroscopic Analysis To Determine The Chemical Composition Of The Precipitate Formed By Mixing Sodium Hypochlorite And Chlorhexidine, James B. Nowicki, Daniel S. Sem

Chemistry Faculty Research and Publications

Introduction—The purpose of this in vitro study was to determine the chemical composition of the precipitate formed by mixing sodium hypochlorite (NaOCl) and Chlorhexidine (CHX), and relative molecular weight of the components.

Methods—Using commercially available chlorhexidine gluconate (CHXg), a 2% solution was formed and mixed in a 1:1 ratio with commercially available NaOCl producing a brown precipitate. The precipitate as well as a mixture of precipitate and pure chlorhexidine diacetate (CHXa) was then analyzed using 1D and 2D NMR spectroscopy.

Results—The 1D and 2D NMR spectra were fully assigned, in terms of chemical shifts of all proton …

Calcium Carbonate And Ammonium Polyphosphate-Based Flame Retardant Composition For Polypropylene, Sarang Deodhar, Kadhiravan Shanmuganathan, Qinguo Fan, Charles A. Wilkie, Maurius C. Costache, Nicholas A. Dembsey, Prabir K. Patra

Chemistry Faculty Research and Publications

The chemical mode of action as a flame retardant of calcium carbonate nanoparticles combined with ammonium polyphosphate in polypropylene was investigated. Reduction in burning rates for 0.5 mm thick samples were observed without appreciable char formation up to 30 wt % loading of additives. Thermogravimetric analysis (TGA) of the mixture of CaCO₃ and ammonium polyphosphate (APP) showed that calcium carbonate nanoparticles react with ammonium polyphosphate before the degradation of the phosphate chains. TGA–FTIR studies of the polymer composite samples and powder mixtures of the additives confirmed the evolution of ammonia and carbon dioxide due to interaction between the additives. …

Anharmonic Properties Of The Vibrational Two-Qubit System, Yingying Gu

Master's Theses (2009 -)

My thesis focuses on theoretical studies in the molecular quantum computing with vibrational qubits. We studied how the molecular vibrational properties affect the fidelity of the logic gates. Our approach is to encode states of the quantum information register into the vibrational eigenstates of a molecule and use the shaped laser pulse (femtosecond, infrared) to control the vibrational state-to-state transition. By using the Optimal Control Theory to shape a femtosecond laser and numerical propagation of laser-driven vibrational wave packets, we analyzed how the vibrational properties of a two-qubit system affect the accuracy of the quantum gates and how to effectively …

Synthetic And Mechanistic Studies On The Cross-Coupling Reactions Catalyzed By Ruthenium Complexes, Ruili Gao

Dissertations (1934 -)

Transition metal catalyzed C-H bond activation reaction is a powerful synthetic method for forming functionalized products directly from unreactive hydrocarbons, and has enormous synthetic potentials for developing chemical processes ranging from petroleum products to pharmaceutical agents. In an attempt to mimic the high stereo selectivity and region selectivity of catalytic reactions by transition metal catalysts, recent research has focused on design and synthesis of transition metal complex and the application on the coupling reactions involving C-H bond activation.

Herein, we wish to report the highly effective coupling reactions involving C-H bond activation by using well-defined ruthenium catalysts. Ruthenium hydride complex …

Eva-Layered Double Hydroxide (Nano)Composites: Mechanism Of Fire Retardancy, Xiaolan Wang, Rajendra Rathore, Ponusa Songtipya, Maria Del Mar Jimenez-Gasco, Evangelos Manias, Charles A. Wilkie

Chemistry Faculty Research and Publications

Composites of ethylene-vinyl acetate copolymer with two different layered double hydroxides have been obtained by melt blending and these have been characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, thermogravimetric analysis connected to mass spectroscopy and cone calorimetry. There is some small difference in dispersion between the zinc-containing and the magnesium-containing layered double hydroxides in EVA, but both these are microcomposites with good dispersion at the micrometer level and relatively poor dispersion at the nanometer level. There is a good reduction in the peak heat release rate at 10% LDH loading. In addition to chain stripping, which involves the …

Synthesis Of Hydroxy- And Polyhydroxy-Substituted 1,3-Diaminocyclohexanes, Anobick Sar, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

The synthesis of hydroxy-trans-1,3-diaminocyclo­hexanes based on nitroso-Diels-Alder cycloaddition of (cyclohexadienyl)phthalimide is reported.

Alteration Of Hydrogen Bonding In The Vicinity Of Histidine 48 Disrupts Millisecond Motions In Rnase A, Nicolet Doucet, Gennady Khirich, Evgenii L. Kovrigin, J. Patrick Loria

Chemistry Faculty Research and Publications

The motion of amino acid residues on the millisecond (ms) time scale is involved in the tight regulation of catalytic function in numerous enzyme systems. Using a combination of mutational, enzymological, and relaxation-compensated ¹⁵N Carr−Purcell−Meiboom−Gill (CPMG) methods, we have previously established the conformational significance of the distant His48 residue and the neighboring loop 1 in RNase A function. These studies suggested that RNase A relies on an intricate network of hydrogen bonding interactions involved in propagating functionally relevant, long-range ms motions to the catalytic site of the enzyme. To further investigate the dynamic importance of this H-bonding network, this …

Direct Patterning Of A Cyclotriveratrylene Derivative For Directed Self-Assembly Of C60, Zachary R. Osner, Dorjderem Nyamjav, Richard C. Holz, Daniel P. Becker

Chemistry Faculty Research and Publications

A novel apex-modified cyclotriveratrylene (CTV) derivative with an attached thiolane-containing lipoic acid linker was directly patterned onto gold substrates via dip-pen nanolithography (DPN). The addition of a dithiolane-containing linker to the apex of CTV provides a molecule that can adhere to a gold surface with its bowl-shaped cavity directed away from the surface, thereby providing a surface-bound CTV host that can be used for the directed assembly of guest molecules. Subsequent exposure of these CTV microarrays to C₆₀ in toluene resulted in the directed assembly of predesigned, spatially controlled, high-density microarrays of C₆₀. The molecular recognition capabilities …

Recent Advances In The Synthetic And Mechanistic Aspects Of The Ruthenium-Catalyzed Carbon-Heteroatom Bond Forming Reactions Of Alkenes And Alkynes, Chae S. Yi

Chemistry Faculty Research and Publications

The group’s recent advances in catalytic carbon-to-heteroatom bond forming reactions of alkenes and alkynes are described. For the C–O bond formation reaction, a well-defined bifunctional ruthenium-amido catalyst has been successfully employed for the conjugate addition of alcohols to acrylic compounds. The ruthenium-hydride complex (PCy₃)₂(CO)RuHCl was found to be a highly effective catalyst for the regioselective alkyne-to-carboxylic acid coupling reaction in yielding synthetically useful enol ester products. Cationic ruthenium-hydride catalyst generated in-situ from (PCy₃)₂(CO)RuHCl/HBF₄·OEt₂ was successfully utilized for both the hydroamination and related C–N bond forming reactions of alkenes. For …

Direct Patterning Of Silanized-Biomolecules On Semiconductor Surfaces, Dorjderem Nyamjav, Richard C. Holz

Chemistry Faculty Research and Publications

A novel approach to pattern silanized-biomolecules directly onto glass (SiO_x) substrates via Dip-Pen nanolithography (DPN) and microcontact printing (μCP) is presented. Subsequent hybridization reactions of DPN patterned silanized-DNA with its complementary strands provide “proof-of-concept” that the patterned oligonucleotides maintain their biological activities. The fabrication strategy does not require premodification of substrates and offers a cheap and robust way to immobilize molecules on electronically important semiconductor surfaces.

Study On Intumescent Flame Retarded Polystyrene Composites With Improved Flame Retardancy, Hongdian Lu, Charles A. Wilkie

Chemistry Faculty Research and Publications

The flame retardancy and thermal stability of ammonium polyphosphate/tripentaerythritol (APP/TPE) intumescent flame retarded polystyrene composites (PS/IFR) combined with organically-modified layered inorganic materials (montmorillonite clay and zirconium phosphate), nanofiber (multiwall carbon nanotubs), nanoparticle (Fe₂O₃) and nickel catalyst were evaluated by cone calorimetry, microscale combustion calorimetry (MCC) and thermogravimetric analysis (TGA). Cone calorimetry revealed that a small substitution of IFR by most of these fillers (≤2%) imparted substantial improvement in flammability performance. The montmorillonite clay exhibited the highest efficiency in reducing the peak heat release rate of PS/IFR composite, while zirconium phosphate modified with C₂₁H_{26 …}

Chelate-Assisted Oxidative Coupling Reaction Of Arylamides And Unactivated Alkenes: Mechanistic Evidence For Vinyl C–H Bond Activation Promoted By An Electrophilic Ruthenium-Hydride Catalyst, Ki Hyeok Kwon, Do W. Lee, Chae S. Yi

Chemistry Faculty Research and Publications

The cationic ruthenium hydride complex [(η⁶-C₆H₆)(PCy₃)(CO)RuH]⁺BF₄⁻ was found to be a highly regioselective catalyst for the oxidative C−H coupling reaction of aryl-substituted amides and unactivated alkenes to give o-alkenylamide products. The kinetic and spectroscopic analyses support a mechanism involving a rapid vinyl C−H activation followed by a rate-limiting C−C bond formation step.

Nmr-Based And Automated Docking Characterization Of Protein Structure, Dynamics, And Ligand Binding, Andrew Lawrence Olson

Dissertations (1934 -)

NMR-based methods used in conjunction with a technique called docking are used to characterize ligand binding to proteins. Standard NMR methods were used to study the backbone dynamics of substrate binding to phosphomevalonate kinase (PMK) and it was observed that ligand binding caused PMK to undergo large conformational changes. These changes were reflected by the appearance of many chemical shift changes upon binding of the natural substrates of PMK (both the binary and ternary complexes) in 1H-15N HSQC NMR titration experiments. The same process was used to characterize the effect ligand binding has on the many arginines in the active …

Detection Of Quercetin Using Polymer Coated Quartz Crystal Microbalance And The Modification Of Á-Zirconium Phosphate To Develop A Sorbent For Organic Pollutant Removal, Darlington Mlambo

Dissertations (1934 -)

Sorption processes involve physical and chemical interactions of sorbents with analytes. These may involve the physical and/or chemical processes in which a substance is accumulated at an interface between two phases, or the intermixing of a substance with the matrix of a second phase. The two processes are referred to as adsorption and absorption respectively. The sorption capacities of different classes of sorbents have many potential and demonstrated applications such as sensor development, water treatment, environmental remediation and chromatographic separations. The goal of this work is to explore the sorption capacity of polymers as well as nanodimensional layered materials for …

The Utility Of Nanocomposites In Fire Retardancy, Linjiang Wang, Xuejun He, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites have been shown to significantly reduce the peak heat release rate, as measured by cone calorimetry, for many polymers but they typically have no effect on the oxygen index or the UL-94 classification. In this review, we will cover what is known about the processes by which nanocomposite formation may bring this about. Montmorillonite will be the focus in this paper but attention will also be devoted to other materials, including carbon nanotubes and layered double hydroxides. A second section will be devoted to combinations of nanocomposite formation with conventional (and unconventional) fire retardants. The paper will conclude with …

The Effect Of Boron-Containing Layered Hydroxy Salt (Lhs) On The Thermal Stability And Degradation Kinetics Of Poly (Methyl Methacrylate), Stephen Majoni, Shengpei Su, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

A boron-containing layered hydroxy salt (LHS), ZHTMDBB, was prepared and compounded with a highly flammable synthetic polymer, poly (methyl methacrylate) {PMMA}, via melt blending: the composite structure was intercalated with poor dispersion. The effect of this LHS on the flammability, thermal stability and degradation kinetics of PMMA was investigated via cone calorimetry and thermogravimetric analysis. The addition of 3-10% by mass of ZHTMDBB to PMMA resulted in significant reduction of peak heat release rate (22-48%) of the polymer and improvements in thermal stability were observed in both air and nitrogen. Effective activation energies for the degradation process were evaluated using …

Chain-Selective And Regioselective Ethylene And Styrene Dimerization Reactions Catalyzed By A Well-Defined Cationic Ruthenium-Hydride Complex: New Insights On The Styrene Dimerization Mechanism, Do W. Lee, Chae S. Yi

Chemistry Faculty Research and Publications

The cationic ruthenium hydride complex [(η⁶-C₆H₆)(PCy₃)(CO)RuH]⁺BF₄⁻ was found to be a highly regioselective catalyst for the ethylene dimerization reaction to give 2-butene products (TOF = 1910 h⁻¹, >95% selectivity for 2-butenes). The dimerization of styrene exclusively produced the head-to-tail dimer (E)-PhCH(CH₃)CH═CHPh at an initial turnover rate of 2300 h⁻¹. A rapid and extensive H/D exchange between the vinyl hydrogens of styrene-d₈ and 4-methoxystyrene was observed within 10 min without forming the dimer products at room temperature. The inverse …

Spectroelectrochemical Studies Of Metalloporphyrins In Room Temperature Ionic Liquid, Yong Soo Hoo

Master's Theses (2009 -)

The oxidation/reduction reactions of porphyrins and metalloporphyrins play an important role in medicinal, industrial and biochemical reactions. Metalloporphyrins are particularly useful as potential catalysts for a variety of processes including catalytic oxidations. The unique properties of metalloporphyrins make them good candidates as electrocatalysts for fuel cells. Metalloporphyrins also play some important roles in biological functions.

By incorporating spectroscopic experiments such as UV-visible or infra-red spectroscopy along with electrochemical experiments such as cyclic voltammetry, one is able to determine the structural changes of the molecule when oxidation or reduction reaction is carried out.

Synthesis And Reactions Of A Tungsten Dioxo Complex, Deborah Bryant

Master's Theses (2009 -)

Metal dioxo complexes are largely known for their ability to epoxidize olefins. The importance of these reactions is reflected in the patents for the ARCO and Halcon processes from the late 1960's. It is very difficult to find literature that shows other indications for metal dioxo complexes.

Catalytic olefin dimerization has become significant in the realm of green chemistry for "atom economical" reactions. Many transition metals have been examined as catalysts for olefin dimerization, but the largest volume of work has been performed using group 8 transition metals, particularly nickel, palladium and platinum. This is especially true for the specific …

X-Ray Structure Of Mer-[Mo(Co)3(Pph3)(Κ2-Dppm)], Shishir Ghosh, Shariff E. Kabir, Faranza K. Camellia, Md. Kamal Hossain, Daniel T. Haworth, Sergey V. Lindeman, Tasneem A. Siddiquee, Dennis W. Bennett

Chemistry Faculty Research and Publications

Treatment of [Mo(CO)₃(NCMe)₃] with bis(diphenylphosphino)methane (dppm) and triphenylphosphine (PPh₃) at 50 °C afforded mer-[Mo(CO)₃(PPh₃)(κ²-dppm)] (1) in 55% yield which has been characterized by single crystal X-ray diffraction studies and spectroscopic measurements. Compound 1 crystallizes in the triclinic space group P−1 with a = 10.3449(6), b = 11.1570(6), c = 17.8961(10) Å, β = 80.8400(10)°, Z = 2 and V = 1959.8(2) ų.