Organic Chemistry Commons^™

Characterization Of Cellulase Enzyme Inhibitors Formed During The Chemical Pretreatments Of Rice Straw, Kalavathy Rajan

Graduate Theses and Dissertations

Production of fuels and chemicals from a renewable and inexpensive resource such as lignocellulosic biomass is a lucrative and sustainable option for the advanced biofuel and bio-based chemical platform. Agricultural residues constitute the bulk of potential feedstock available for cellulosic fuel production. On a global scale, rice straw is the largest source of agricultural residues and is therefore an ideal crop model for biomass deconstruction studies. Lignocellulosic biofuel production involves the processes of biomass conditioning, enzymatic saccharification, microbial fermentation and ethanol distillation, and one of the major factors affecting its techno-economic feasibility is the biomass recalcitrance to enzymatic saccharification. Preconditioning …

Novel [3,3]- And [1,3]- Rearrangements Of Azole-Derived N,X-Ketene Acetals, Sefat A. Alwarsh

Graduate Theses and Dissertations

The formation of carbon-carbon bonds in organic chemistry is fundamentally important. One of the major reactions that chemists have widely investigated is the Claisen rearrangement. Based on the fundamental features of this rearrangement, chemists exploited the capability of the transformation and invented their own variations of Claisen-type rearrangements. Our goal in this project is to develop a novel variation of the Claisen rearrangement using azole compounds, which are common heteroaromatic ring systems that are present extensively in the biomedically important natural products. We propose here novel methodologies of preparing 2-substitution azole derivatives using aza-based Claisen rearrangement, N,X-ketene acetals that requires …

Low-Level Mercury Causes Inappropriate Activation In T And B Lymphocytes In The Absence Of Antigen Stimulation, K. L. Weigand, J. L. Reno, B. M. Rowley

Journal of the Arkansas Academy of Science

The immune system primarily utilizes two cell types for adaptive immunity: T lymphocytes and B lymphocytes. T lymphocytes are activated when antigen presenting cells (APCs) present antigen to membrane-bound T cell receptors. B lymphocytes are activated when an antigen binds to receptors embedded in the plasma membrane. In both T and B cells this antigen binding crosslinks the receptor complexes and initiates the signal transduction cascade. These cascades frequently consist of a series of intracellular molecules becoming phosphorylated in a step-wise fashion. Once activated, these cells differentiate into effector cells that clear out the stimulating antigen. Mercury, which is a …

Bond Length - Bond Valence Relationships For Carbon - Carbon And Carbon - Oxygen Bonds, C. Harris, F. D. Hardcastle

Journal of the Arkansas Academy of Science

In the present study, relationships are developed for determining bond orders (also referred to as bond valences or bond numbers) from published bond lengths for carbon-carbon (C-C) and carbon-oxygen (C-O) bonds. The relationships are based on Pauling’s empirical formula s = exp((Ro-R)/b)), where s is the bond order, R is the corresponding bond length, Ro is the unit valence bond length, and b is a fitting parameter. We use a recently derived relationship for the b parameter in terms of the bonding atoms’ published atomic orbital exponents. The resulting equations were checked against published x-ray diffraction (XRD) data for 176 …

Wave Profile For Anti-Force Waves With Maximum Possible Currents, M. Hemmati, R. Horn, W. P. Childs, A. K. Meredith

Journal of the Arkansas Academy of Science

In the theoretical investigation of the electrical breakdown of a gas, we apply a one-dimensional, steady state, constant velocity, three component fluid model and consider the electrons to be the main element in propagation of the wave. The electron gas temperature, and therefore the electron gas partial pressure, is considered to be large enough to provide the driving force. The wave is considered to have a shock front, followed by a thin dynamical transition region. Our set of electron fluid-dynamical equations consists of the equations of conservation of mass, momentum, and energy, plus the Poisson's equation. The set of equations …

Oxidative Stability Of Conjugated Linoleic Acid Rich Soy Oil Obtained By Heterogeneous Ruthenium Catalysis, Saurabh Ravindra Lele

Graduate Theses and Dissertations

Conjugated linoleic acid (CLA) has multiple health benefits but it is difficult to obtain sufficient CLA in a healthy diet to obtain the clinical effects. A CLA rich-soy oil (CLARSO) with up to 20% CLA has been produced by heterogenous catalysis but no studies of its oxidative stability have been reported. CLARSO and soy oil primary and secondary oxidation products were measured at 50oC in the dark. The CLARSO was less stable than soy oil but adsorption bleaching improved its oxidative stability. However, induction times were dependent on the analytical method used. Fatty acid oxidation kinetics was determined by measuring …

Visible Light Mediated Intermolecular [3 + 2] Annulation Of Cyclopropylanilines With Alkynes, Theresa H. Nguyen, Soumitra Maity, Nan Zheng

Chemistry & Biochemistry Faculty Publications and Presentations

Intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes is realized using visible light photoredox catalysis, yielding a variety of cyclic allylic amines in fair to good yields. This method exhibits significant group tolerance particularly with heterocycles. It can also be used to prepare complex heterocycles such as fused indolines.

Low Speed Current Bearing Anti-Force Waves, M. Hemmati, W. P. Childs, H. Shojaei, H. Morris

Journal of the Arkansas Academy of Science

For theoretical investigation of electrical breakdown of a gas, we apply a one-dimensional, steady profile, constant velocity, three-component (electrons, ions and neutral particles) fluid model. Our fluid model consists of the equations of conservation of mass, momentum and energy, coupled with the Poison’s equation. The set of equations is referred to as the electron fluid dynamical equations (EFD). This investigation involves breakdown waves with a substantial current behind the wave front, and waves for which the electric field force on electrons is in the opposite direction of the wave propagation (anti-force waves – lightning return stroke). Therefore, the set of …

Evaluating N-Benzylgalactonoamidines As Putative Transition State Analogs For Β-Galactoside Hydrolysis, Qui-Hua Fan, Susanne Striegler, Rebekah Langston, James Barnett

Chemistry & Biochemistry Faculty Publications and Presentations

Experimental evidence is provided for p-methylbenzyl-D-galactonoamidine to function as a true transition state analog for the enzymatic hydrolysis of aryl-β-D-galactopyranosides by β-galactosidase (A. oryzae). The compound exhibits inhibition constants in the low nanomolar concentration range (12–56 nM) for a selection of substrates. Along these lines, a streamlined synthetic method based on phase-transfer catalysis was optimized to afford the required variety of new aryl-β-D-galactopyranosides. Last, the stability of the galactonoamidines under the assay conditions was confirmed.

Visible-Light Photocatalyzed Cross-Linking Of Diacetylene Ligands By Quantum Dots To Improve Their Aqueous Colloidal Stability, Marion G. Götz, Hiroko Takeuchi, Matthew J. Goldfogel, Julia M. Warren, Brandon D. Fennel, Colin D. Heyes

Chemistry & Biochemistry Faculty Publications and Presentations

Ligand cross-linking is known to improve the colloidal stability of nanoparticles, particularly in aqueous solutions. However, most cross-linking is performed chemically, in which it is difficult to limit interparticle cross-linking, unless performed at low concentrations. Photochemical cross-linking is a promising approach but usually requires ultraviolet (UV) light to initiate. Using such high-energy photons can be harmful to systems in which the ligand–nanoparticle bond is fairly weak, as is the case for the commonly used semiconductor quantum dots (QDs). Here, we introduce a novel approach to cross-link thiolated ligands on QDs by utilizing the photocatalytic activity of QDs upon absorbing visible …

Towards The Total Synthesis Of Antascomicin B. Efforts To Construct The C1-C21 Fragment, Juliette Rivero-Castro

Graduate Theses and Dissertations

Antascomicin B is a macrolide isolated from a strain of Micromonospora. It possesses structural similarities to FK506 and rapamycin and exhibits potent binding ability to FKBP12. Recent reports suggest that small molecule ligands of FKBP12 possess potent neuroprotective and neurodegenerative properties in mouse models of Parkinson's disease. Our approach to the C1-21 fragment of antascomicin B involves an asymmetric amino-Claisen rearrangement originally developed by Tsunoda et al.35 report the scalability of the preparation and rearrangement of an allylic amide possessing a silyloxy group at the terminal position of the alkene. The Tsunoda-Claisen rearrangement uses inexpensive (S)-α-methylbenzylamine as the chiral …

Tin Sensitization For Electroless Plating, Xingfei Wei

Graduate Theses and Dissertations

The tin sensitization process has been used in electroless plating since 1940s Brenner and Riddell developed the electroless plating for surface metallization method. It was found to be an interesting topic to study tin sensitization for chemically controlling metal deposition on different substrates, because the tin sensitization process had critical effects on the electroless plated metal thin films. Nowadays electroless plating metal deposition is still an important method for depositing metals. It has a few advantages over the vapor deposition and electrodeposition method, such as work in an ambient condition, on nonconductive substrates, and without extra power input. Applying electroless …

Developing A Presumptive Test For Select Synthetic Cannabinoids, Carrie Snyder

Graduate Theses and Dissertations

Synthetic cannabinoids (SC's) began to gain popularity around the world in 2009. Since then, many of the compounds have been outlawed and methods developed to detect them and their metabolites using mass spectrometry. Our work investigated the possibility of developing a colorimetric presumptive test. The SC JWH-019 was synthesized and its ketone targeted as a possible reaction site. Many SC's contain ketones and thus a reaction at this site would be applicable to many of the compounds. Since JWH-019 is costly and time consuming to synthesize, much of the experimental work was done using benzophenone (BP). BP contains a diaryl …

Synthesis Of Platinum And Platinum-Copper Branched Nanoparticles For Electrooxidation Of Methanol, Eric Courtland Taylor

Graduate Theses and Dissertations

Platinum and Pt alloys are among the most important heterogeneous catalysts for many organic reactions and electrochemical reactions associated with the fuel cell technologies. How to reduce Pt usage while maintaining the performance of the catalysts becomes a subject for intensive research in materials chemistry. For heterogeneous catalysis, the catalytic reactivity and selectivity are strongly correlated with different crystallographic facets exposed on the surface. The facets with high-index planes whose Miller indices with at one is larger than unity are generally more active than those with low-index planes (e.g., {100}, {111}, and {110}). Tuning the morphology of the nanoparticles to …

Further Studies On The Allylic Diazene Rearrangement, Maha Laxmi Shrestha

Graduate Theses and Dissertations

Former graduate student Wei Qi and Professor Matt McIntosh have reported diastereoselective reductive 1,3-transpositions of acyclic alpha, beta-unsaturated tosyl hydrazones to afford substrates with a 1,4-syn or 1,4-anti relationship between alkoxy and methyl groups that proceed via an ADR (Qi, W.; McIntosh, M. C. Org. Lett. 2008, 10, 357; Qi, W.; McIntosh, M. C. Tetrahedron 2008, 64, 7021). In these reports, silica gel was employed to accelerate the reduction. We have found that acetic acid gives the same results with high diastereoselectivity in the reaction. We further optimized the reaction by lowering the amount of catecholborane to 3 eq. Effects …

Wave Profile For Current Bearing Antiforce Waves, H. Morris, W. Childs, P. Pinkston, M. Hemmati, J. Christensen

Journal of the Arkansas Academy of Science

For fluid dynamical analysis of breakdown waves, we employ a one-dimensional, three-component (electrons, ions and neutral particles) fluid model to describe a steady-state, ionizing wave propagating counter to strong electric fields. The electron gas temperature and therefore the electron fluid pressure is assumed to be large enough to sustain the wave motion down the discharge tube. Such waves are referred to as antiforce waves. The complete set of equations describing such waves consists of the equations of conservation of mass, momentum and energy coupled with Poisson’s equation. Inclusion of current behind the wave front alters the set of electron fluid …

Microwave Assisted Synthesis Of Chloropentahaptocyclopentadienediphenylphosphinoethaneruthenium(Ii), S. Muthyala, Mark Draganjac

Journal of the Arkansas Academy of Science

No abstract provided.

Molecular Structure Of Pentahaptocyclopentadienebis (Tetrahydrothiophene) Triphenylphosphineruthenium(Ii) Triflate, Paul M. Nave, Mark Draganjac, A. W. Cordes

Journal of the Arkansas Academy of Science

No abstract provided.

New Applications Of Mass Spectrometry For Drug And Lipid Analysis, Elizabeth Lauren Emerson

Graduate Theses and Dissertations

Mass spectrometry is an important tool used in many different disciplines and settings that include forensics, drug discovery, environmental analysis, and proteomics. Gas chromatography - mass spectrometry (GC-MS) and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI - TOF MS) are two of the most important instruments used for analysis of compounds. Chapters 1 and 2 of this discussion use GC-MS for the investigation of synthetic cannabinoids in `K2' incense products and the detection of metabolites in urine samples from individuals suspected of consuming these mixtures. Analytical standards were synthesized and used for identification and confirmation of structures. Detection of …

Semiconductor Nanocrystals: From Quantum Dots To Quantum Disks, Zheng Li

Graduate Theses and Dissertations

The bottom-up colloidal synthesis opened up the possibility of finely tuning and tailoring the semiconductor nanocrystals. Numerous recipes were developed for the preparation of colloidal semiconductor nanocrystals, especially the traditional quantum dots. However, due to the lack of thorough understanding to those systems, the synthesis chemistry is still on the empirical level. CdS quantum dots synthesis in non-coordinating solvent were taken as a model system to investigate its molecular mechanism and formation process, ODE was identified as the reducing agent for the preparation of CdS nanocrystals, non-injection and low-temperature synthesis methods developed. In this model system, we not only proved …

Part I - A Study Of The Formation Of Carbenes By Elimination Of Α-Bromosilanes And Application Toward The Synthesis Of Transition Metal Complexed Quinone Methide Analogs. Part Ii - Development Of Novel 7-Membered Ring Carbene Ligands For Palladium Catalyzed Cross Coupling Reactions., Christian Michael Loeschel

Graduate Theses and Dissertations

In part I, we wish to report our approaches toward transition metal complexed ortho-quinone methide analogs. ortho-Quinone Methides are a class of highly reactive compounds with a wide range of chemical and biological applications. Previously, a stable iron complexed benzannulated 5-membered ring quinone methide analog was reported by Allison and Neal27. Herein, we report our approaches to improve the reactivity of that system by removing benzannulation as well as changing the metal from iron to manganese and rhenium.

Furthermore, a methodological study on generating carbenes under mild conditions by elimination of α-halosilanes and its application towards metal complexed quinone methide …

Studies Toward The Total Synthesis Of Antascomicin B, David Ross Clay

Graduate Theses and Dissertations

The following dissertation describes synthetic efforts toward the synthesis of the C21-C34 fragment of antascomicin B. Our initial enzymatic approach is detailed as well as an asymmetric transfer hydrogenation (ATH) strategy that will be used in the eventual total synthesis of the molecule. Several investigations into anomalies observed during (ATH) reactions are also discussed.

The Design, Synthesis And Application Of A Novel Class Of N-Heterocyclic Carbene Catalysts, Abigail Lynn Hubbard

Graduate Theses and Dissertations

A copper carbenoid representative of a novel class of N-heterocyclic carbene (NHC) catalysts has been synthesized. This compound was characterized by X-ray crystallography and was found to confirm the rationale of our synthetic design: The C2-symmetric structure places four stereocenters in close proximity (<5Å) to the reactive site of the carbene via a trans-annular gearing effect. The copper carbenoid was found to catalyze the hydrosilylation of prochiral ketones with superb selectivity in high yield.

Dynamics And Catalytic Resolution Of Selected Chiral Organolithiums, Timothy Kum Beng

Graduate Theses and Dissertations

One of the most important developments of the last decade has been the emergence of new methods to dynamically resolve racemic organolithiums using stoichiometric amounts of the chiral ligand. When this concept is implemented successfully, it obviates the need for covalently attached chiral auxiliary based methods, asymmetric deprotonation, and asymmetric synthesis of a precursor stannane as ways to access enantioenriched organolithium compounds for use in asymmetric synthesis. Since certain electrophiles consume the chiral ligand, it is desirable to render this process catalytic in the chiral ligand.

As part of a larger study on the amenability of chiral organolithiums to a …

Studies Toward The Development Of A Microelectrode Array For Detection Of Dopamine Through Redox Cycling, Anupama Aggarwal

Graduate Theses and Dissertations

Redox cycling is an electrochemical technique that cycles the reversible redox species between its oxidative states repeatedly on generator and collector electrodes. Two or more individually-addressable microelectrodes located close to each other allow redox cycling to be possible. Electrochemical behavior of a biologically important molecule, dopamine is examined under redox cycling conditions. To our knowledge, this is the first report on detection of physiological concentration of dopamine in presence of up to 100 times excess ascorbate with the use of redox cycling, without the involvement of polymer coating such as Nafion®.

Microfabrication was used to produce different geometries (parallel bands …

Synthesis, Characterization, And Properties Of Homometallic Dinuclear Ruthenium Complex Containing Chloro-Phenanthroline And Bipyridine, A. A. Bhuiyan, S. Kudo

Journal of the Arkansas Academy of Science

This paper deals with the synthesis and spectroscopic investigation of homometallic dinuclear ruthenium(II) complex containing chlorophenanthroline and bipyridine ligands. This bimetallic ruthenium polypyridine complex may be useful for biological electron transfer studies. Heteroleptic ruthenium monomer complex Ru(bpy)2(Cl-phen) (where bpy = 2,2’-bipyridine and Cl-phen = 5-chloro- 1,10-phenanthroline) was prepared in a two step procedure previously developed in our laboratory. This monomer complex was used to prepare the ruthenium dimer complex, (bpy)2Ru(phen-phen)Ru(bpy)2, by utilizing the Ni-catalyzed coupling reaction. Both the complexes were purified by column chromatography. The identity and the integrity of the complexes were confirmed by elemental analysis as well as …

Density Functional Studies Of The Structure And Bonding In Piano Stool Carbene Complexes, John P. Graham, Robbie Davis

Journal of the Arkansas Academy of Science

No abstract provided.

Computational Study Of A Novel Dinuclear Metal Complex, Dragos Seghete

Inquiry: The University of Arkansas Undergraduate Research Journal

The first compound containing an M-H-M was recently reported by Vicic et al. With recent availability of large computational resources, molecular modeling has become a reliable tool for confirming experimental results. The novel dinuclear Ni complex [( dippm)2Ni2Br2]( 0 -H) was investigated in this work from a theoretical perspective. Full geometry optimization was carried on the dinuclear Ni complex at the DFT/B3LYP with the 6-31G* basis set. The result verifies the linear Ni-H-Ni bond. Two different starting structures that converged to the same geometry confirm that a global minimum was reached. The computed structure differs from the experimentally determined one …

Studies Of Zeolite Entrapped Ruthenium Polypyridine Complexes, Anwar A. Bhuiyan

Journal of the Arkansas Academy of Science

There is an intense interest in designing molecular systems which will absorb visible sunlight, initiate an electron transfer process, and ultimately convert the solar energy to useful chemical energy of fuels such as hydrogen produced from water. The zeolite-entrapped polypyridine complexes of divalent ruthenium hold promise as efficient photocatalysts for net charge separation and such efficiencies are further enhanced by organized incorporation of donor and acceptor components. This paper deals with the synthesis and spectroscopic investigation of zeolite-entrapped ruthenium polypyridine complexes which may be useful in the development of solar energy conversion schemes. The sensitizer molecules, such as Ru(bpy)3 2+ …

The Effects Of Multiple Mutations In The Hydrophobic Core Upon The Stability Of Staphylococcal Nuclease, Rebecca L. Danforth

Inquiry: The University of Arkansas Undergraduate Research Journal

Previous work in the laboratory of my research advisor, Dr. Wesley Stites, has investigated the core packing of the protein staphylococcal nuclease. The core of a protein is critical in determining a protein's structure and stability. The hydrophobicity of the core has long been thought to be the principal driving force for folding, but recent work in the Stites lab has shown that optimization of van der Waals contacts and minimization of cavities, in our shorthand term, packing, is at least as energetically important. We are building upon this information in our attempt to better pack the protein core. If …