Chemistry Commons^™

Enhanced Acidity Of Acetic And Pyruvic Acids On The Surface Of Water, Alexis J. Eugene, Elizabeth A. Pillar, Agustín J. Colussi, Marcelo I. Guzman

Chemistry Faculty Publications

Understanding the acid–base behavior of carboxylic acids on aqueous interfaces is a fundamental issue in nature. Surface processes involving carboxylic acids such as acetic and pyruvic acids play roles in (1) the transport of nutrients through cell membranes, (2) the cycling of metabolites relevant to the origin of life, and (3) the photooxidative processing of biogenic and anthropogenic emissions in aerosols and atmospheric waters. Here, we report that 50% of gaseous acetic acid and pyruvic acid molecules transfer a proton to the surface of water at pH 2.8 and 1.8 units lower than their respective acidity constants pK_{a …}

Infra-Red Microwave Spectra, Overtones, Degeneracy And Thermal Populations All In One Diagram, Carl W. David

Chemistry Education Materials

An old drawing, which had an error in it, is re-presented (corrected) for understanding the relationships in diatomic vibrational-rotational interactions at the introductory level.

Evidence For The Formation Of A Radical-Mediated Flavin-N5 Covalent Intermediate, Yumin Dai, Hannah Valentino, Pablo Sobrado

Chemistry Faculty Research & Creative Works

The redox-neutral reaction catalyzed by 2-haloacrylate hydratase (2-HAH) leads to the conversion of 2-chloroacrylate to pyruvate. Previous mechanistic studies demonstrated the formation of a flavin-iminium ion as an important intermediate in the 2-HAH catalytic cycle. Time-resolved flavin absorbance studies were performed in this study, and the data showed that the enzyme is capable of stabilizing both anionic and neutral flavin semiquinone species. The presence of a radical scavenger decreases the activity in a concentration-dependent manner. These data are consistent with the flavin iminium intermediate occurring by radical recombination.

Platinum@Hexaniobate Nanopeapods: Sensitized Composite Architectures For Photocatalytic Hydrogen Evolution Under Visible Light Irradiation, Clare Davis-Wheeler Chin

LSU New Orleans Theses and Dissertations

Hydrogen fuel is one of the most important areas of research in the field of renewable energy development and production. Hydrogen gas can be generated by fuel cells, water electrolyzers, and heterogeneous nanoscale catalysts. It can be burned to directly release chemical energy or condensed for storage and transport, providing fuel for combustion devices or storing excess energy generated by renewable sources such as wind turbines and concentrated solar power assemblies. While platinum is the most active catalyst for hydrogen reduction, its high cost significantly deters its utilization in advanced photocatalytic materials. One approach to mitigating this expense is optimizing …

Thiophene-Based Molecular Sensors Towards The Selective Detection Of Mercury(Ii) And Other Metals, Austin Kazuo Shigemoto

Dissertations and Theses

This work describes several thiophene-based molecular sensors and various modifications aimed to improve and understand the photophysical and supramolecular properties, such as the association constant (K_a) and selectivity, towards the development of a selective mercury(II) sensor. From the first generation of sensors containing pyridine and thiophene groups, it was determined that thiophene can offer good selectivity for mercury(II) against other transition metal ions, and provide a ratiometric absorption and fluorescent response. The projects following this focused on improving the K_a of the first generation of sensors through several different strategies. Substitution of thiophene for dibenzothiophene was …

Fabrication Of Mnox/Mwcnts-Gc Nanocatalyst For Oxygen Evolution Reaction, Yaser M. Asal Mr, Islam M. Al-Akraa Dr, Amr M. Arafa Eng.

Chemical Engineering

Manganese oxide (MnOx) and multiwalled carbon nanotubes (MWCNTs) are intended to modify the GC electrode for oxygen evolution reaction (OER). Optimization of MnOx loading is carried out and the deposition of 55 cycles was sufficient to obtain the highest activity toward OER. The stability of the catalyst is enhanced by the addition of MWCNTs. As a result, an amount of 22 kWh/Kg of O₂ of energy is saved. Several techniques including cyclic voltammetry, linear sweep voltammetry, chronoamperometry, chronopotentiometry, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy will be combined to track the catalyst activity and to determine its …

Light Absorption By Polar And Non-Polar Aerosol Compounds From Laboratory Biomass Combustion, Deep Sengupta, Vera Samburova, Chiranjiva Bhattarai, Elena Kirillova, Lynn Mazzoleni, Michealene Iaukea-Lum, Adam Watts, Audrey Khlystov

Department of Chemistry Publications

Fresh and atmospherically aged biomass-burning (BB) aerosol mass is mostly comprised of strongly light-absorbing black carbon (BC) and of organic carbon (OC) with its light-absorbing fraction – brown carbon (BrC). There is a lack of data on the physical and chemical properties of atmospheric BB aerosols, leading to high uncertainties in estimates of the BB impact on air quality and climate, especially for BrC. The polarity of chemical compounds influences their fate in the atmosphere including wet/dry deposition and chemical and physical processing. So far, most of the attention has been given to the water-soluble (polar) fraction of BrC, while …

Role Of Stone-Wales Defects On The Interfacial Interactions Among Graphene, Carbon Nanotubes, And Nylon 6: A First-Principles Study, Sanjiv K. Jha, Michael Roth, Guido Todde, J. Paige Buchanan, Robert D. Moser, Manoj K. Shukla, Gopinath Subramanian

Faculty Publications

We investigate computationally the role of Stone-Wales (SW) defects on the interfacial interactions among graphene, carbon nanotubes (CNTs), and Nylon 6 using density functional theory (DFT) and the empirical force-field. Our first-principles DFT calculations were performed using the Quantum ESPRESSO electronic structure code with the highly accurate van der Waals functional (vdW-DF2). Both pristine and SW-defected carbon nanomaterials were investigated. The computed results show that the presence of SW defects on CNTs weakens the CNT-graphene interactions. Our result that CNT-graphene interaction is much stronger than CNT-CNT interaction indicates that graphene would be able to promote the dispersion of CNTs in …

Ultrafast Laser Filament-Induced Fluorescence Spectroscopy Of Uranyl Fluoride, P. J. Skrodzki, M. Burger, L. A. Finney, F. Poineau, S. M. Balasekaran, J. Nees, K. R. Czerwinski, I. Jovanovic

Chemistry and Biochemistry Faculty Research

Uranyl fluoride (UO2F2) is a compound which forms in the reaction between water and uranium hexafluoride, a uranium containing gas widely used for uranium enrichment. Uranyl fluoride exhibits negligible natural background in atmosphere; as a result, its observation implies the presence and active operation of nearby enrichment facilities and could be used as a tracer for treaty verification technologies. Additionally, detection of UO2F2 has a potential application in guiding remediation efforts around enrichment facilities. Laser-induced fluorescence (LIF) has been proposed in the past as a viable technique for the detection and tracking of UO2F2. We demonstrate that ultrafast laser filamentation …

Examining The Effects Of Amino And Thiolate Ligands On The Reactivity And Selectivity Of Palladium On Carbon In Hydrogenation Reactions, Eric Liu, Christina Li

The Summer Undergraduate Research Fellowship (SURF) Symposium

Heterogeneous catalysts are used widely by chemical and energy industries because they show high reactivity but often suffer from lack of selectivity. On the other hand, ligands are commonly used in homogeneous catalysts to control the reactivity and selectivity; however, the effects of the ligands on the steric and electronic properties of heterogeneous catalysts are less understood. We examine the effects of four different ligands: 1-adamantanethiol, 1-adamantylamine, 1-dodecanethiol, and 1-dodecylamine, for the commercial hydrogenation catalyst palladium on carbon. Hydrogenation reactions are used as a screening tool to see the behavior that the different catalysts exhibit in the presence of unsaturated …

Electronic Effect Of Platinum Alloy Catalysts On Olefin Hydrogenation Kinetics, Colin Reedy, Jeff Miller, Stephen Purdy

The Summer Undergraduate Research Fellowship (SURF) Symposium

Dehydrogenation of alkanes is the first step in transforming light hydrocarbons into liquid fuels and chemicals. This process has traditionally used platinum alloys as catalysts. Alloys are used industrially because they have a greater selectivity than monometallic platinum. Alloying platinum with an inactive promoter modifies the crystalline structure of the surface (geometric effect), and the 5d electrons in platinum responsible for chemistry (electronic effect); both have been suggested to be primarily responsible for dehydrogenation selectivity in platinum alloys. Alloy catalysts have been synthesized using early 3d transition metal promoters with the same Pt₃M crystal structure. X-Ray Absorption Spectroscopy …

Thienoisatin Oligomers As N-Type Molecular Semiconductors, Natalie M. Kadlubowski, Xuyi Luo, Jianguo Mei

The Summer Undergraduate Research Fellowship (SURF) Symposium

Organic field effect transistors (OFETs) offer many advantages compared to traditional inorganic transistors, such as flexibility and solution processability. In this study we design and synthesize two thienoisatin-based organic semiconducting small molecules, then investigate their electronic properties in n-type OFETs. To introduce n-type charge transport, electron-withdrawing dicarbonitrile moieties were installed on thienoisoindigo and bis-thienoisatin molecules, which led to a quinoidal conjugation on thienoisoindigo, while maintaining an aromatic conjugation on the bis-thienoisatin. Following the syntheses, the molecules were characterized to determine highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels via cyclic voltammetry, as well as any potential …

Alkene Ozonolysis In The Academic Lab, Patrick Dussault

Organic Peroxides: Safety Issues

The following information is offered as a guide based upon our experience with application of ozone for organic oxidations and hydroperoxide synthesis. Please send suggestions, requests, or corrections to [email protected].

Introduction and leading references

Overview of ozonolysis: Mechanism, Substrate reactivity, Typical reaction conditions, Reaction monitoring, Reaction work-ups

Safety Issues

Acknowledgements:

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The following provides a brief introduction to the application of ozonolysis within academic labs. Ozonolysis remains among the most frequently used of methods for oxidative cleavage of alkenes. While best known as a means by which to introduce aldehydes and ketones, ozonolysis can also be used to generate other …

Tof-Sims Analysis Of Plant Seed Interactions With Plant Growth-Promoting Bacteria, Tammy Pheuphong, Rachel Komorek, Xiao-Ying Yu

STAR Program Research Presentations

The use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) in plant biology is a relatively unexplored and quickly developing field. The majority of research in plant SIMS involves the application of ToF-SIMS to study dried wood tissues, and only a handful of studies apply SIMS on plant stems, roots, and/or seeds. Our project provides a brief description and review of previous work using SIMS on plant stems, roots, and/or seeds, along with an emphasis on the sample preparation in each study. Additionally, the use of Brachypodium distachyon (Brachypodium) as a model system for research on grasses has also become more …

Applications Of Diels-Alder Chemistry In Polymer Synthesis, Joshua C. Stambaugh, Philip J. Costanzo, Sierra E. Gosting

STAR Program Research Presentations

Diels-Alder chemistry is utilized for a myriad of commercial applications during polymer synthesis, ranging from self-healing materials to heat responsive materials to emulsion coatings. In particular, the ability to regulate and control the amount and type of functional group linkages is key component for polymer applications. A common strategy that is employed is the use of phenolic maleimide as a dienophile during Diels-Alder synthesis to control the linkages on a polymer, which determines its properties and functionality. This summer was the beginning of a project to prepare a commercial scale, water-based emulsion floor coating/polish. The first step in this project …

Anisotropic Conductive Adhesives For Interdigitated Back Contact (Ibc) Silicon Solar Cells, Katherine M. Lohmuste, Manuel Schnabel, Maikel F.A.M. Van Hest

STAR Program Research Presentations

The current manufacturing process for solar panels using interdigitated back contact (IBC) silicon solar cells involves a multi-step metallization and interconnection process in which a substantial amount of silver is used. This work focuses on a new process using conductive adhesives (CA) which would increase efficiency and lower cost through a one-step metallization and interconnection process that combines with encapsulation using little silver and only requiring metal patterning on the back sheet or back glass. It would also not require direct metallization of the silicon, which would result in fewer defects, while increasing voltage and therefore efficiency. Silver-coated Poly(Methyl Methacrylate) …

Fuel Specific Emissions Trends For In-Use Medium And Heavy-Duty Vehicle Fleets In California, Molly J. Haugen

Electronic Theses and Dissertations

New heavy-duty vehicle regulations have caused significant reductions in hazardous air pollutants, such as particulate matter (PM) and nitrogen oxides (NO_x), due to better engine management and utilization of advanced after-treatment systems. The University of Denver has collected data for gaseous and PM emission measurements from on-road heavy-duty vehicles (HDVs). The On-Road Heavy-Duty Vehicle Emissions Measurement System (OHMS) collected fuel specific emission information on individual HDVs of in-use fleets at two California locations in the spring of 2013, 2015 and 2017. These complimentary fleets, studied over multiple years, produced 7,075 measurements of gaseous and particle emission data providing …

Crystal Structures Of 2-Bromo-1,1,1,3,3,3-Hexa­Methyl-2-(Tri­Methyl­Sil­Yl)Tris­Ilane And 2-Bromo-1,1,1,3,3,3-Hexa­Isopropyl-2-(Triiso­Propyl­Sil­Yl)Tri­Silane, Eva Gulotty, Richard Staples, Shannon Biros, Peter Gaspar, Nigam Rath, William Winchester

Chemistry & Biochemistry Faculty Works

The synthesis and crystal structures of two tris­(tri­alkyl­sil­yl)silyl bromide compounds, C9H27BrSi4 (I, HypSiBr) and C27H63BrSi4 (II, TipSiBr), are described. Compound I was prepared in 85% yield by free-radical bromination of 1,1,1,3,3,3-hexa­methyl-2-(tri­methyl­sil­yl)tris­ilane using bromo­butane and 2,2′-azobis(2-methyl­propio­nitrile) as a radical initiator at 333 K. The mol­ecule possesses threefold rotational symmetry, with the central Si atom and the Br atom being located on the threefold rotation axis. The Si—Br bond distance is 2.2990 (12) Å and the Si—Si bond lengths are 2.3477 (8) Å. The Br—Si—Si bond angles are 104.83 (3)° and the Si—Si—Si bond angles are 113.69 (2)°, reflecting the steric hindrance …

Imaging The Surface Of A Hand-Colored 19th Century Daguerreotype., Madalena S Kozachuk, Maria O Avilés, Ronald R Martin, Brianne Potts, Tsun-Kong Sham, François Lagugné-Labarthet

Chemistry Publications

Daguerreotypes are valued artifacts that constitute a unique historical photographic memory of the 19th century. Understanding their surface chemistry is important in order to conserve and, when necessary, to restore them. Colored highlights were often added by hand to emphasize different features on the daguerreotype's subjects. In the present work, we report on a daguerreotype that was hand-colored with a red pigment that was added to the cheeks of the two individuals. A series of experiments using micro-Raman and micro-Fourier transform infrared spectroscopy and synchrotron-based X-ray fluorescence microscopy and absorption spectroscopy are used to analyze the surface and to determine …

Manganese Oxide/Hemin-Functionalized Graphene As A Platform For Peroxynitrite Sensing, Haitham F. Kalil, Shaimaa Maher, Tiyash Bose, Mekki Bayachou

Chemistry Faculty Publications

Peroxynitrite (ONOO−, PON) is a powerful oxidizing agent generated in vivo by the diffusion-limited reaction of nitric oxide (NO) and superoxide (O₂˙⁻) radicals. Under oxidative stress, cumulated peroxynitrite levels are associated with chronic inflammatory disorders and other pathophysiological conditions. The accurate detection of peroxynitrite in biological systems is important, not only to understand the genesis and development of diseases, but also to explore and design potential therapeutics. Herein, a manganese oxide/hemin-modified graphene interface is explored as a platform for peroxynitrite amperometric detection. Hemin-functionalized reduced graphene oxide was further modified with manganese oxide nanoparticles to provide a …

Safe Use Of Hydrogen Peroxide In The Organic Lab, Patrick Dussault

Organic Peroxides: Safety Issues

The article describes good practices for use of hydrogen peroxide (H₂O₂) in an organic lab setting. Major headings include:

Leading references; Toxicity; Physical properties; Chemical properties; Stability and incompatibilities; Confinement/pressure; and, References to accidents involving H₂O₂.

Cell-Free Studies Of Catalytic Dna Cleavage By Ruthenium Polypyridyl Complexes (Rpcs) Containing Redox-Active Intercalating Ligands, Enantiomeric Separation And Semi-Prep Scale Purification Of Rpcs, Cynthia Ann Griffith

Chemistry & Biochemistry Dissertations - Archive

Herein, we report the ruthenium (II) polypyridyl complexes (RPCs), [(phen)₂Ru(tatpp)] ²⁺ (3²⁺) and [(phen)₂Ru(tatpp)Ru(phen)₂] ⁴⁺ (4⁴⁺) are shown to cleave DNA in cell-free studies in the presence of a mild reducing agent, i.e. glutathione (GSH), in a manner that is enhanced upon lowering the [O₂] . Reactive oxygen species (ROS) are involved in the cleavage process as hydroxy radical scavengers attenuate the cleavage activity. Cleavage experiments in the presence of superoxide dismutase (SOD) and catalase reveal a central role for H₂O₂ as the immediate precursor for hydroxy radicals. A mechanism is proposed which explains the inverse [O₂] dependence and ROS …

New Methods For Discovery, Fingerprinting, And Analysis Of Cannabis Sativa Natural Products, Allegra Leghissa

Chemistry & Biochemistry Dissertations - Archive

Cannabis sativa is an herbaceous annual that has always been of great interest due to its uses in the manufacturing of textiles and cordage, as well as for its medicinal properties. The two main bioactive components of C. sativa are cannabinoids and terpenes; the former confer the medicinal and pharmaceutical benefits, as well as the psycho-activity, to the plant, while the latter are largely responsible for aroma and flavor. Because of the importance of both sets of analytes, it is crucial to have a comprehensive understanding and characterization of these compounds, and different methods have been developed to address these …

New Strategies For Catalytic C-H And Olefin Hydrosilylation, Parham Asgari

Chemistry & Biochemistry Dissertations - Archive

In the works described here, new catalytic hydrosilylation strategies were explored. First, a highly selective, bond functionalization strategy, achieved via relay of two transition metal catalysts and use of traceless acetal directing groups, was introduced. Specifically, this approach involves the relay of Ir-catalyzed hydrosilylation and Rh-catalyzed ortho-C–H silylation. This acetal directing group strategy was used for catalytic ortho-C–H silylation of phenols and benzoate esters derivatives. Additionally, we developed a transition metal free, catalytic vinyl arenes hydrosilylation method. We describe our discovery on unprecedented, sustainable HAT process and report a mechanism involving Lewis base-catalyzed, complexation-induced HAT (LBCI-HAT), followed by highly selective …

Novel Relative Spontaneous Ignition Temperature Determination Using Carbon Dioxide Onset With Sta/Ir, Antonio David Trevino

Electronic Theses and Dissertations

Simultaneous thermal analysis, coupled with infrared spectroscopy (STA/IR), was utilized to monitor the evolution of gaseous products during the thermal degradation of samples from Triadica sebifera (Chinese tallow), Ligustrum sinense (Chinese privet), and Ilex vomitoria (yaupon) plants. Identification of carbon dioxide was successful with a spectral match of 90.2 percent and further used in the determination of relative spontaneous ignition temperature, or RSIT. The RSIT value during the growing season for Chinese tallow, Chinese tallow stem, Chinese privet, and Yaupon were 208.4°C, 250.3°C, 210.1°C, and 232.3°C respectively. During the dormant seasons, the values for Chinese tallow stem, Chinese privet, and …

Computational Study Of The Nature Of Tetrel Bond, Yama Aman

Masters Theses

For more than a hundred years, the type of a chemical bond has been distinguished according to the relative electronegativities of chemical units at the ends of a bond. Whereas, the bond of unequally electronegative on both ends is called a polar covalent or even ionic bond or a non-polar covalent bond in case of both equal. Regardless the type of bonded elements, the whole idea for the bond was believed to be electron driven only. In the 20th century the development of the idea, that not just the electronic relation but specific elements are also able to characterize the …

Studies Towards The Total Synthesis Of Imidazole-Containing Natural Products, Lawton Anthony Ii Seal

Chemistry & Biochemistry Dissertations - Archive

Nature has inspired man in all aspects of life, chemistry included. The first antibiotic ever discovered came from nature, and since then, chemists have been probing nature for insights to guide drug discovery and development. Alkaloids are a class of naturally occurring molecules which contain nitrogen atoms and can be found in all forms of life. Imidazole is common structural unit found in many natural molecules, from the simple amino acid histamine to more complex structures like the marine sponge derived alkaloid palau’amine. Many imidazole-containing natural products are biologically active, such as inhibiting the growth of tumors, possessing antibacterial properties, …

Separation, Detection, And Quantitation Of Underivatized Carbohydrates Using Liquid Chromatography- Electrospray Ionization-Triple Quadrupole- Tandem Mass Spectrometry, Jonathan B. Thacker

Chemistry & Biochemistry Dissertations - Archive

Carbohydrate analysis has many important implications in health, consumer products, and industrial processes. Among many possible analytical techniques for their analysis, mass spectrometry (MS) is an attractive approach, offering high sensitivity and specificity. In particular, electrospray ionization (ESI)-MS affords several advantages over other ionization techniques: the ability for direct coupling with upstream chemical separation techniques, its suitability for quantitation, and its compatibility with relatively inexpensive quadrupole mass analyzers for the analysis of high molecular weight compounds. However, the sensitivity of ESI-MS towards carbohydrates tends to be much less than for other classes of compounds, such as peptides. This is due …

Characterization And Remediation Of Wastewater From Unconventional Oil And Gas Development, Tiffany Michelle Liden

Chemistry & Biochemistry Dissertations - Archive

Increasing energy demands from the nation and technological advancement in well development have led to the rapid expansion of unconventional oil and gas extraction. Current disposal methods for wastewater generated from the development of low porosity formations are not environmentally sustainable. The billions of gallons of highly variable, chemically-rich wastewater, referred to as produced water, is frequently sequestered in subsurface, non-productive stratum through injection wells. Cost-effective options to treat produced water are being sought as an alternative to injection wells to prevent the loss of water from the water cycle and decrease anthropologically induced seismic events. Ultimately, it has been …

Redox And Non-Redox Reactions Catalyzed By Biomimetic Flavin-Based Organocatalysts And The Discovery Of Selective Oxidation Methods For The Preparation Of N-Heterocycles, Pawan Thapa

Chemistry & Biochemistry Dissertations - Archive

In nature, flavoproteins (FMN and FAD) are known to catalyze several chemical transformations which play a vital role in the growth, development, and survival of organisms. They are involved in one-electron and two-electron transfer reactions, photo-induced electron transfer reactions, dehydrogenase reactions, oxidative atom transfer reactions and also rare non-redox reactions. Their enhanced stability and ability to turn over in presence of dioxygen has inspired synthetic chemists, including our group, to perform biomimetic transformations within a range of function of natural flavoproteins. In chapter 1, both intramolecular and intermolecular dehydrogenative coupling between the alpha carbon of tertiary amines and various nitrogen, …