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- Photochemistry (4)
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Articles 1 - 30 of 35
Full-Text Articles in Analytical Chemistry
A New Lc-Ms/Ms Technique For Separation Of Gangliosides Using A Phenyl-Hexyl Column: Systematic Separation According To Sialic Acid Class And Ceramide Subclass, Ashta Lakshmi Prasad Gobburi, Eric Wekesa Kipruto, Denise M. Inman, David J. Anderson
A New Lc-Ms/Ms Technique For Separation Of Gangliosides Using A Phenyl-Hexyl Column: Systematic Separation According To Sialic Acid Class And Ceramide Subclass, Ashta Lakshmi Prasad Gobburi, Eric Wekesa Kipruto, Denise M. Inman, David J. Anderson
Chemistry Faculty Publications
A LC-MS/MS technique separated the bovine and mouse brain gangliosides monosialotetrahexosylgangliosides (GM1), disialotetrahexosylgangliosides (GD1a), trisialotetrahexosylgangliosides (GT1b) and tetrasialotetrahexosylgangliosides (GQ1b) using a phenyl-hexyl HPLC column and employing a linear methanol gradient in water, which is 0.028% in ammonium hydroxide. The gangliosides were separated according to sialic acid class, and within a particular class, gangliosides having different ceramide carbon chain lengths were also separated. All gangliosides of a particular sialic acid class eluted in characteristic retention time windows in the order of GQ1b, (earliest), GT1b, GD1a, and GM1 (latest). Within each specific retention time window for a particular ganglioside class, gangliosides were …
Production Of Singlet Oxygen (1O2) During The Photochemistry Of Aqueous Pyruvic Acid: The Effects Of Ph And Photon Flux Under Steady-State O2(Aq) Concentration, Alexis J. Eugene, Marcelo I. Guzman
Production Of Singlet Oxygen (1O2) During The Photochemistry Of Aqueous Pyruvic Acid: The Effects Of Ph And Photon Flux Under Steady-State O2(Aq) Concentration, Alexis J. Eugene, Marcelo I. Guzman
Chemistry Faculty Publications
The photochemistry of pyruvic acid (PA) in aqueous atmospheric particles contributes to the production of secondary organic aerosols. This work investigates the fate of ketyl and acetyl radicals produced during the photolysis (λ ≥ 305 nm) of 5-100 mM PA under steady state [O2(aq)] = 260 μM (1.0 ≤ pH ≤ 4.5) for photon fluxes between 1 and 10 suns. The radicals diffuse quickly into the water/air interface of microbubbles and react with dissolved O2 to produce singlet oxygen (1O2*). Furfuryl alcohol is used to trap and bracket the steady-state production of …
The Effects Of Reactant Concentration And Air Flow Rate In The Consumption Of Dissolved O2 During The Photochemistry Of Aqueous Pyruvic Acid, Alexis J. Eugene, Marcelo I. Guzman
The Effects Of Reactant Concentration And Air Flow Rate In The Consumption Of Dissolved O2 During The Photochemistry Of Aqueous Pyruvic Acid, Alexis J. Eugene, Marcelo I. Guzman
Chemistry Faculty Publications
The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. …
An Overview Of Dynamic Heterogeneous Oxidations In The Troposphere, Elizabeth A. Pillar-Little, Marcelo I. Guzman
An Overview Of Dynamic Heterogeneous Oxidations In The Troposphere, Elizabeth A. Pillar-Little, Marcelo I. Guzman
Chemistry Faculty Publications
Due to the adverse effect of atmospheric aerosols on public health and their ability to affect climate, extensive research has been undertaken in recent decades to understand their sources and sinks, as well as to study their physical and chemical properties. Atmospheric aerosols are important players in the Earth’s radiative budget, affecting incoming and outgoing solar radiation through absorption and scattering by direct and indirect means. While the cooling properties of pure inorganic aerosols are relatively well understood, the impact of organic aerosols on the radiative budget is unclear. Additionally, organic aerosols are transformed through chemical reactions during atmospheric transport. …
Oxidation Of Substituted Catechols At The Air-Water Interface: Production Of Carboxylic Acids, Quinones, And Polyphenols, Elizabeth A. Pillar, Marcelo I. Guzman
Oxidation Of Substituted Catechols At The Air-Water Interface: Production Of Carboxylic Acids, Quinones, And Polyphenols, Elizabeth A. Pillar, Marcelo I. Guzman
Chemistry Faculty Publications
Anthropogenic activities contribute benzene, toluene, and anisole to the environment, which in the atmosphere are converted into the respective phenols, cresols, and methoxyphenols by fast gas-phase reaction with hydroxyl radicals (HO(•)). Further processing of the latter species by HO(•) decreases their vapor pressure as a second hydroxyl group is incorporated to accelerate their oxidative aging at interfaces and in aqueous particles. This work shows how catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol (all proxies for oxygenated aromatics derived from benzene, toluene, and anisole) react at the air-water interface with increasing O3(g) during τc ≈ 1 μs contact time and contrasts their …
Reactivity Of Ketyl And Acetyl Radicals From Direct Solar Actinic Photolysis Of Aqueous Pyruvic Acid, Alexis J. Eugene, Marcelo I. Guzman
Reactivity Of Ketyl And Acetyl Radicals From Direct Solar Actinic Photolysis Of Aqueous Pyruvic Acid, Alexis J. Eugene, Marcelo I. Guzman
Chemistry Faculty Publications
The variable composition of secondary organic aerosols (SOA) contributes to the large uncertainty for predicting radiative forcing. A better understanding of the reaction mechanisms leading to aerosol formation such as for the photochemical reaction of aqueous pyruvic acid (PA) at λ ≥ 305 nm can contribute to constrain these uncertainties. Herein, the photochemistry of aqueous PA (5-300 mM) continuously sparged with air is re-examined in the laboratory under comparable irradiance at 38° N at noon on a summer day. Several analytical methods are employed to monitor the time series of the reaction, including (1) the derivatization of carbonyl (C═O) functional …
Aqueous Photochemistry Of Glyoxylic Acid, Alexis J. Eugene, Sha-Sha Xia, Marcelo I. Guzman
Aqueous Photochemistry Of Glyoxylic Acid, Alexis J. Eugene, Sha-Sha Xia, Marcelo I. Guzman
Chemistry Faculty Publications
Aerosols affect climate change, the energy balance of the atmosphere, and public health due to their variable chemical composition, size, and shape. While the formation of secondary organic aerosols (SOA) from gas phase precursors is relatively well understood, studying aqueous chemical reactions contributing to the total SOA budget is the current focus of major attention. Field measurements have revealed that mono-, di-, and oxo-carboxylic acids are abundant species present in SOA and atmospheric waters. This work explores the fate of one of these 2-oxocarboxylic acids, glyoxylic acid, which can photogenerate reactive species under solar irradiation. Additionally, the dark thermal aging …
Photocatalytic Reduction Of Fumarate To Succinate On Zns Mineral Surfaces, Ruixin Zhou, Marcelo I. Guzman
Photocatalytic Reduction Of Fumarate To Succinate On Zns Mineral Surfaces, Ruixin Zhou, Marcelo I. Guzman
Chemistry Faculty Publications
The reductive tricarboxylic acid (rTCA) cycle is an important central biosynthetic pathway that fixes CO2 into carboxylic acids. Among the five reductive steps in the rTCA cycle, the two-electron reduction of fumarate to succinate proceeds nonenzymatically on the surface of photoexcited sphalerite (ZnS) colloids suspended in water. This model reaction is chosen to systematically study the surface photoprocess occurring on ZnS in the presence of [Na2S] (1–10 mM) hole scavenger at 15 °C. Experiments at variable pH (5–10) indicate that monodissociated fumaric acid is the primary electron acceptor forming the monoprotic form of succinic acid. The following …
Heterogeneous Oxidation Of Catechol, Elizabeth A. Pillar, Ruixin Zhou, Marcelo I. Guzman
Heterogeneous Oxidation Of Catechol, Elizabeth A. Pillar, Ruixin Zhou, Marcelo I. Guzman
Chemistry Faculty Publications
Natural and anthropogenic emissions of aromatic hydrocarbons from biomass burning, agro-industrial settings, and fossil fuel combustion contribute precursors to secondary aerosol formation (SOA). How these compounds are processed under humid tropospheric conditions is the focus of current attention to understand their environmental fate. This work shows how catechol thin films, a model for oxygenated aromatic hydrocarbons present in biomass burning and combustion aerosols, undergo heterogeneous oxidation at the air–solid interface under variable relative humidity (RH = 0–90%). The maximum reactive uptake coefficient of O3(g) by catechol γO3 = (7.49 ± 0.35) × 10–6 occurs for …
Synthesis And Flammability Testing Of Epoxy Functionalized Phosphorous-Based Flame Retardants, Vladimir Benin, Xuemei Cui, Alexander Morgan, Karl Seiwert
Synthesis And Flammability Testing Of Epoxy Functionalized Phosphorous-Based Flame Retardants, Vladimir Benin, Xuemei Cui, Alexander Morgan, Karl Seiwert
Chemistry Faculty Publications
Several potential new phosphorus-containing flame retardant molecules were evaluated for heat release reduction potential by incorporation of the molecules into a polyurethane, generated from methylene diphenyl diisocyanate and 1,3-propane diol. The heat release reduction potential of these substances was evaluated using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods to qualitatively evaluate their potential reactivity into the polyurethane prior to heat release testing. The functionality of the flame retardants was epoxide based that would potentially react with the diol during polyurethane synthesis. Flammability testing …
Catechol Oxidation By Ozone And Hydroxyl Radicals At The Air-Water Interface, Elizabeth A. Pillar, Robert C. Camm, Marcelo I. Guzman
Catechol Oxidation By Ozone And Hydroxyl Radicals At The Air-Water Interface, Elizabeth A. Pillar, Robert C. Camm, Marcelo I. Guzman
Chemistry Faculty Publications
Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air–water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon …
Heat Release Of Polyurethanes Containing Potential Flame Retardants Based On Boron And Phosphorus Chemistries, Vladimir Benin, Bastien Gardelle, Alexander Morgan
Heat Release Of Polyurethanes Containing Potential Flame Retardants Based On Boron And Phosphorus Chemistries, Vladimir Benin, Bastien Gardelle, Alexander Morgan
Chemistry Faculty Publications
Using a polyurethane of methylene diphenyl isocyanate and 1,3-propane diol, several new non-halogenated aromatic boron and phosphorus flame retardants were evaluated for heat release reduction potential using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods, and were then analyzed via spectroscopic methods to determine if the flame retardant was still present in the final product. PCFC testing on the resulting products showed that the flame retardant molecule can have different effects on heat release depending upon how it is mixed into the polyurethane. Some …
Determination Of Corrosion Inhibitor Lubricity Improver In Jet Fuel By Liquid Chromatography-Electrospray Ionization Mass Spectrometry, David W. Johnson, Milissa Flake, Ryan Adams
Determination Of Corrosion Inhibitor Lubricity Improver In Jet Fuel By Liquid Chromatography-Electrospray Ionization Mass Spectrometry, David W. Johnson, Milissa Flake, Ryan Adams
Chemistry Faculty Publications
Military jet fuel (JP-8) is very similar to commercial jet fuel (Jet A) except for the presence of three additives, fuel system icing inhibitor, corrosion inhibitor–lubricity improver (CI-LI), and antistatic additive, which are added to improve characteristics of JP-8. Of particular interest is the CI-LI additive; the most common active ingredient is a dimer of linoleic acid. This article focuses on quantification of the active ingredient in the CI-LI additive by liquid chromatography–mass spectrometry (LC–MS). This method will allow the determination of CI-LI content in military jet fuel samples.
Science Classics, Mark Masthay
Science Classics, Mark Masthay
Chemistry Faculty Publications
An essay on the impact of the works in the Imprints and Impressions: Milestones in Human Progress, an exhibition of rare books from the collection of Stuart Rose. Exhibition was held Sept. 29-Nov. 9, 2014, at the University of Dayton.
Phosphate Esters, Thiophosphate Esters And Metal Thiophosphates As Lubricant Additives, David W. Johnson, John E. Hils
Phosphate Esters, Thiophosphate Esters And Metal Thiophosphates As Lubricant Additives, David W. Johnson, John E. Hils
Chemistry Faculty Publications
Phosphate esters, thiophosphate esters and metal thiophosphates have been used as lubricant additives for over 50 years. While their use has been extensive, a detailed knowledge of how they work has been a much more recent development. In this paper, the use of phosphate esters and thiophosphate esters as anti-wear or extreme pressure additives is reviewed with an emphasis on their mechanism of action. The review includes the use of alkyl phosphates, triaryl phosphates and metal containing thiophosphate esters. The mechanisms of these materials interacting with a range of iron and steel based bearing material are examined.
Structure, Theoretical Studies And Coupling Reactions Of Some New Cyclic Boronic Esters, Andrew Kuttler, Sravanthi Durganala, Albert Fratini, Alexander Morgan, Vladimir Benin
Structure, Theoretical Studies And Coupling Reactions Of Some New Cyclic Boronic Esters, Andrew Kuttler, Sravanthi Durganala, Albert Fratini, Alexander Morgan, Vladimir Benin
Chemistry Faculty Publications
The present report describes the X-ray structural and theoretical studies of some new pinacolboronate esters, and it also outlines the use of the target structures in Suzuki coupling reactions to produce new aromatic or heteroaromatic esters and amides. X-ray structural analysis of the studied compounds revealed that the pinacolborane ring's position with respect to the benzene ring varies, depending on the particular environment. An ortho-positioned carboxylic ester (methyl ester) causes a nearly perpendicular orientation of the pinacolborane unit with respect to the benzene ring, whereas an ortho-positioned amide (N,N-dimethylamide) causes the pinacolborane unit to orient itself nearly coplanar. A plausible …
Characterization By Nmr Of Reactants And Products Of Hydrofluoroether Isomers, Cf3(Cf2)3och3 And (Cf3)2c(F)Cf2och3, Reacting With Isopropyl Alcohol, Howard Knachel, Vladimir Benin, William E. Moddeman, Janine C. Birkbeck, Thomas A. Kestner, Tayna L. Young
Characterization By Nmr Of Reactants And Products Of Hydrofluoroether Isomers, Cf3(Cf2)3och3 And (Cf3)2c(F)Cf2och3, Reacting With Isopropyl Alcohol, Howard Knachel, Vladimir Benin, William E. Moddeman, Janine C. Birkbeck, Thomas A. Kestner, Tayna L. Young
Chemistry Faculty Publications
The 3M Company product Novec™ 71IPA DL, a mixture of methoxyperfluorobutane, methoxyperfluoroisobutane and 4.5 wt.% isopropyl alcohol, has been found to be very stable at ambient temperature, producing fluoride at the rate of ~1 ppm/year. Our earlier kinetic and theoretical studies have identified the reaction mechanism. This paper identifies the 1H and 19F NMR chemical shifts, multiplicities, and coupling constants of reactants and the major products that result from aging the mixture in sealed Pyrex NMR tubes for periods up to 1.8 years at temperatures from 26 °C to 102 °C. Chemical shifts and coupling constants of fluorine …
Interaction Between Lubricants Containing Phosphate Ester Additives And Stainless Steels, David W. Johnson, Matthew Bachus, John E. Hils
Interaction Between Lubricants Containing Phosphate Ester Additives And Stainless Steels, David W. Johnson, Matthew Bachus, John E. Hils
Chemistry Faculty Publications
One way to improve fuel efficiency in today’s jet aircraft engines is to create an environment for higher operating temperatures and speeds. New and improved lubricants and bearing materials must be developed to remain stable in these elevated operating temperatures. Three lubricants, with varying amounts of tricresyl phosphate added as an anti-wear/extreme pressure additive were tested on two different stainless steels at varying temperatures ranging from 300 °C to 350 °C in vacuum. Significant decomposition of the lubricant base-stocks and the phosphate ester additive did occur in most of the trials resulting in the formation of carboxylic acids and phenols. …
Preparation Of Phosphonoterephthalic Acids Via Palladium-Catalyzed Coupling Of Aromatic Iodoesters, Nathaniel Ivan, Vladimir Benin, Alexander Morgan
Preparation Of Phosphonoterephthalic Acids Via Palladium-Catalyzed Coupling Of Aromatic Iodoesters, Nathaniel Ivan, Vladimir Benin, Alexander Morgan
Chemistry Faculty Publications
The current article reports in detail the preparation of two phosphonoterephthalic acids: 2-phosphonoterephthalic acid (1) and 2,5-diphosphonoterephthalic acid (2). Efficient, scalable syntheses have been developed for both compounds based on Pd-catalyzed coupling reactions of iodinated terephthalate esters. Phosphonoterephthalic acids are potentially useful as flame-retardant additives or as monomers for the construction of acid-pendant polymer chains.
Reaction Between Polyol-Esters And Phosphate Esters In The Presence Of Metal Carbides, David W. Johnson, Carolyn Iacullo, John E. Hils
Reaction Between Polyol-Esters And Phosphate Esters In The Presence Of Metal Carbides, David W. Johnson, Carolyn Iacullo, John E. Hils
Chemistry Faculty Publications
The reaction of metal carbides with polyol esters found in aerospace lubricants and phosphate esters commonly used as additives was investigated. Carbides were of particular interest since modern materials under consideration at high temperature bearings have surfaces that are primarily metal carbides. Vanadium and chromium carbide were found to react with the ester and phosphate ester by a transesterification reaction, producing an alkyl phosphate which is less stable than the aromatic phosphate esters. In the process, the metal carbide is converted to the metal phosphate and metal polyphosphate, evidenced by the infrared and Raman spectra of the solid residue and …
En Route Towards Α-Benzotriazoyl Nitroso Derivatives, Jean-Christophe M. Monbaliu, Lucas K. Beagle, Judit K. Beagle, Matthias Zeller, Christian V. Stevens, Alan R. Katritzky
En Route Towards Α-Benzotriazoyl Nitroso Derivatives, Jean-Christophe M. Monbaliu, Lucas K. Beagle, Judit K. Beagle, Matthias Zeller, Christian V. Stevens, Alan R. Katritzky
Chemistry Faculty Publications
A new class of geminally-substituted nitroso compounds, i.e., α-benzotriazoyl nitroso derivatives, is presented. These compounds display a rather different behavior than other related nitroso compounds bearing a geminal electron-withdrawing group. An unexpected and spontaneous oxidation to the nitro analog is observed in solution.
Reactions Of Methyl Perfluoroalkyl Ethers With Isopropyl Alcohol: Experimental And Theoretical Studies, Howard Knachel, Vladimir Benin, Chadwick Barklay, Janine C. Birkbeck, Billy D. Faubion, William E. Moddeman
Reactions Of Methyl Perfluoroalkyl Ethers With Isopropyl Alcohol: Experimental And Theoretical Studies, Howard Knachel, Vladimir Benin, Chadwick Barklay, Janine C. Birkbeck, Billy D. Faubion, William E. Moddeman
Chemistry Faculty Publications
The reaction of an isomeric mixture of the methyl perfluoroalkyl ether, C4F9OCH3 (Novec-7100), in the presence of isopropyl alcohol (IPA) and/or water has been studied by measuring the rate of product formation using an ion-selective electrode (ISE) for fluoride ion, Karl Fisher coulometric titrations for water, and 1H and 19F NMR spectroscopy for product identification and rate studies. The results showed the methyl perfluoroalkyl ether to be very stable with products forming at the rate of ∼1 ppm per year at a laboratory temperature of 20 °C. Measurements over the temperature range of 6° to 100 °C were made on …
Synthesis And Flame Retardant Testing Of New Boronated And Phosphonated Aromatic Compounds, Vladimir Benin, Sravanthi Durganala, Alexander Morgan
Synthesis And Flame Retardant Testing Of New Boronated And Phosphonated Aromatic Compounds, Vladimir Benin, Sravanthi Durganala, Alexander Morgan
Chemistry Faculty Publications
The present report describes the preparation and use of some dimethyl terephthalate derivatives in transition metal-catalyzed coupling reactions to produce new reactive flame retardants. Dimethyl iodoterephthalate and dimethyl 2,5-diiodoterephthalate were successfully employed in the preparation of phosphonic and boronic esters and acids. The latter were tested for heat release with a microcombustion calorimeter (ASTM D7309) to determine the potential for heat release reduction of these flame retardant molecules. The results showed that the addition of boronic or phosphonic acids greatly lowered the heat release, due to a condensed phase (char formation) mechanism. Adding ester groups to the boronic acids or …
The Tetrafluoroborate Salt Of 4-Methoxybenzyl N-2-(Dimethylamino)Ethyl-N-Nitrosocarbamate: Synthesis, Crystal Structure And Dft Calculations, Helene Hedian, Vladimir Benin
The Tetrafluoroborate Salt Of 4-Methoxybenzyl N-2-(Dimethylamino)Ethyl-N-Nitrosocarbamate: Synthesis, Crystal Structure And Dft Calculations, Helene Hedian, Vladimir Benin
Chemistry Faculty Publications
The tetrafluoroborate salt of 4-methoxybenzyl N-2-(dimethylamino)ethyl-N-nitrosocarbamate was prepared in two steps, via the corresponding carbamate. Its crystal structure is monoclinic, space group P21/c. The unit cell dimensions are: a = 19.499(8) Å, b = 5.877(3) Å, c = 15.757(7) Å, α = 90°, β = 110.019(7)°, γ = 90°, V = 1696.5(12) Å3, Z = 4. The structure exhibits an unexpected, pseudo-gauche conformation with respect to the C2–C3 bond, due to a stabilizing hydrogen bond between the carbonyl oxygen (O1) and the hydrogen atom at the trialkylammonium center (H3n), with a distance between them of …
Application Of Raman Spectroscopy To Lubricants, Lubricated Surfaces And Lubrication Phenomena, David W. Johnson
Application Of Raman Spectroscopy To Lubricants, Lubricated Surfaces And Lubrication Phenomena, David W. Johnson
Chemistry Faculty Publications
Recent advances in lasers and detector technologies and the development of low-cost instruments and fiber-optic probes have brought about an explosion in the lubrication systems being studied by Raman spectroscopy. This article provides examples of the use of Raman spectroscopy in the study of lubrication phenomena, including the characterization of liquid lubricants, lubricant additives, and solid lubricants; the study of vapor-phase lubrication; and the use of coated nanoparticles as lubricants.
A Sodium Salt Of The Dimer Of Boronoterephthalic Acid Anhydride, Scott Simmons, Albert Fratini, Vladimir Benin
A Sodium Salt Of The Dimer Of Boronoterephthalic Acid Anhydride, Scott Simmons, Albert Fratini, Vladimir Benin
Chemistry Faculty Publications
The title compound, sodium bis(6-carboxy-1-hydroxy-3-oxo-1,3-dihydro-2,1-benzoxaborol-1-yl)oxidanium, Na+·C16H15B2O13-, was prepared in two steps from 2-bromo-p-xylene. Its crystal structure was determined at 140 K and has triclinic (P) symmetry. The compound presents a unique structural motif, including two units of the cyclic anhydride of boronoterephthalic acid, joined by a protonated, and thereby trivalent, oxonium center. Association in the crystal is realized by complementary hydrogen bonding of the carboxyl groups, as well as by coordination of the sodium cations to the oxygen centers on the five-membered rings.
Theoretical Investigation Of A Reported Antibiotic From The 'Miracle Tree' Moringa Oleifera, Michael Horwath, Vladimir Benin
Theoretical Investigation Of A Reported Antibiotic From The 'Miracle Tree' Moringa Oleifera, Michael Horwath, Vladimir Benin
Chemistry Faculty Publications
Moringa oleifera, sometimes called the “Miracle Tree,” has received international attention for its potential to improve health in impoverished tropical areas. In addition to high vitamin content in the leaves and pods, the tree contains compounds with antioxidant and antibacterial properties. This study focused on the theoretical investigation of the suggested structure of one antibacterial compound, “pterygospermin,” whose existence was proposed after some studies of the roots of M. oleifera. The structure of pterygospermin was first proposed by a research group working in the 1950s, but later studies have not found evidence of this compound and have instead …
Preparation And Characterization Of Some Substituted Benzyl N-Nitrosocarbamates Containing An N-2-(Methylthio)Ethyl Or A Bis(2-Aminoethyl)Sulfide Functionality, Satya Venkata, Eric Shamo, Vladimir Benin
Preparation And Characterization Of Some Substituted Benzyl N-Nitrosocarbamates Containing An N-2-(Methylthio)Ethyl Or A Bis(2-Aminoethyl)Sulfide Functionality, Satya Venkata, Eric Shamo, Vladimir Benin
Chemistry Faculty Publications
The synthesis and characterization of some substituted benzyl N-nitrosocarbamates with an N-2-(methylthio)ethyl or a bis(2-aminoethyl)sulfide functionality is reported, as a part of a long-term goal to design and prepare novel photolabile structures that could be used as substances for controlled release of alkylating and/or crosslinking agents. The synthesis was accomplished by reaction of benzyl chloroformates with the corresponding amines, resulting in the preparation of carbamates. The latter were subsequently nitrosated, utilizing two different N-nitrosation methods, to yield the target structures.
Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis
Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis
Chemistry Faculty Publications
Chlorination and bromination reactions of thiazolo[5,4-d]thiazole led to the generation of its mono- and dihalogenated derivatives. These are the first instances of successful direct electrophilic aromatic substitution in the thiazolo[5,4-d]thiazole ring system. X-ray analysis demonstrates that both 2-bromothiazolo[5,4-d]-thiazole and 2,5-dibromothiazolo[5,4-d]thiazole are planar structures, with strongly manifested π-stacking in the solid state. Theoretical analysis of the pyridine-catalyzed halogenation (MP2/6-31+G(d) and B3LYP/6-31+G(d)calculations) reveals that introduction of one halogen actually leads to a slightly enhanced reactivity towards further halogenation. Several halogenation mechanisms have been investigated: 1) The direct C-halogenation with N-halopyridine as electrophile; …
C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin
C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin
Chemistry Faculty Publications
The current report presents the first theoretical study of the restricted CN bond rotation in carbamoyl chlorides. Several N-benzyl-N-methylcarbamoyl chlorides were investigated, with varying pattern of substitution in the aromatic ring. Optimizations and frequency calculations were conducted employing DFT at the B3LYP/6-31+G(d) level of theory. Each of the studied structures exhibits a pair of rotamers (s-Z and s-E), generated upon rotation around the C(O)N bond. The s-E isomer is the global minimum in every case, but the preference for it is usually less than 1 kcal/mol. Two possible transition state structures were identified …