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Articles 138751 - 138780 of 303797
Full-Text Articles in Physical Sciences and Mathematics
Design And Synthesis Of Novel Chloroquine-Based Antimalarials, Kevin Vincent Murphy
Design And Synthesis Of Novel Chloroquine-Based Antimalarials, Kevin Vincent Murphy
Dissertations and Theses
Malaria is an infectious, often fatal disease that afflicts nearly 200 million people every year. The disease, characterized by recurring and extreme flu-like symptoms, is caused by the protozoan parasite Plasmodium falciparum. Victims usually contract the disease through a mosquito vector. Chloroquine is a chemotherapeutic that was introduced in the 1940s. For many years the drug was the foremost treatment of malaria, being effective and producing few side effects. Unfortunately, tolerance to chloroquine developed when the parasite evolved a resistance mechanism. Newer drugs have been developed and implemented, but these medicines also show a decreasing effect with continued administration. …
Evaluation Of Low-Cost Low Impact Development Practices In Southwest Florida For The Control Of Urban Runoff, Laura Kathren Rankin
Evaluation Of Low-Cost Low Impact Development Practices In Southwest Florida For The Control Of Urban Runoff, Laura Kathren Rankin
USF Tampa Graduate Theses and Dissertations
Stormwater management is required due to development and alteration of the natural environment. It is heavily regulated in Florida and at the national level. Over the last two decades, Low Impact Development (LID) has been promoted as a sustainable and environmentally friendly method of controlling urban runoff. Case studies, provided in Chapter 2, show that LIDs can restore watershed hydrology by balancing the water budget. The difference in runoff between pre-development and post-development appears to increase with soil perviousness. However, the potential for mitigating the impacts of urbanization through runoff reduction is also greater for pervious, sandy soils that dominate …
Land-Use & Water Quality In The Headwaters Of The Alafia River Watershed, Jaime Alison Swindasz
Land-Use & Water Quality In The Headwaters Of The Alafia River Watershed, Jaime Alison Swindasz
USF Tampa Graduate Theses and Dissertations
The objective of this study is to investigate land-use changes and water quality trends within the headwaters of the Alafia River watershed. Water quality data were obtained from the Environmental Protection Commission of Hillsborough County (EPCHC). Eleven water quality parameters selected for analysis included: temperature (˚C), dissolved oxygen (DO), percent saturation of DO, conductivity, pH, total phosphorous (TP), total nitrogen (TN), ammonium, chlorophyll-a (uncorrected), fecal coliforms, and enterococci. ArcMap® & SWFWMD data were used to map EPCHC sampling stations, calculate contributing watershed size, and determine land-use changes over the course of the sampling period; 17 stations were chosen for this …
U.S. Drought Monitor, November 3, 2015, David Miskus
U.S. Drought Monitor, November 3, 2015, David Miskus
United States Agricultural Commodities in Drought Archive
Drought map of U.S. for November 3, 2015 (11/3/15) plus: U.S. crop areas experiencing drought (map), Approximate percentage of crop located in drought, by state (bar graph), Percent of crop area located in drought, past 52 weeks (line graph) for: Corn, Soybeans, Hay, Cattle, Winter wheat.
Exploring Rapid Radiochemical Separations At The University Of Tennessee Radiochemistry Center Of Excellence, Howard L. Hall, John D. Auxier Ii
Exploring Rapid Radiochemical Separations At The University Of Tennessee Radiochemistry Center Of Excellence, Howard L. Hall, John D. Auxier Ii
Faculty Publications and Other Works -- Institute for Nuclear Security
The University of Tennessee formed its Radiochemistry Center of Excellence (RCoE) in 2013 with support from the U.S. National Nuclear Security Administration. One of the major thrusts of the RCoE is to develop deeper understanding of rapid methods for radiochemical separations that are relevant to both general radiochemical analyses as well as post-detonation nuclear forensics. Early work has included the development and demonstration of rapid separations of lanthanide elements in the gas phase, development of a gas-phase separation front-end for ICP-TOF-MS analysis, and the development of realistic analytical surrogates for post-detonation debris to support methods development.
Street-Level Predictive Modeling Of Nuisance Flooding Verified Via Crowdsourced App Data In Norfolk, Va, J. D. Loftis, H. V. Wang, D R. Forrest
Street-Level Predictive Modeling Of Nuisance Flooding Verified Via Crowdsourced App Data In Norfolk, Va, J. D. Loftis, H. V. Wang, D R. Forrest
Presentations
No abstract provided.
Resonant Quantum Dynamics Of Few Ultracold Bosons In Periodically Driven Finite Lattices, Simeon I. Mistakidis, T. Wulf, A. Negretti, P. Schmelcher
Resonant Quantum Dynamics Of Few Ultracold Bosons In Periodically Driven Finite Lattices, Simeon I. Mistakidis, T. Wulf, A. Negretti, P. Schmelcher
Physics Faculty Research & Creative Works
The Out-Of-Equilibrium Dynamics Of Finite Ultracold Bosonic Ensembles In Periodically Driven One-Dimensional Optical Lattices Is Investigated. Our Study Reveals That The Driving Enforces The Bosons In Different Wells To Oscillate In-Phase And To Exhibit A Dipole-Like Mode. A Wide Range From Weak-To-Strong Driving Frequencies Is Covered And A Resonance-Like Behavior Of The Intra-Well Dynamics Is Discussed. In The Proximity Of The Resonance A Rich Intraband Excitation Spectrum Is Observed. The Single Particle Excitation Mechanisms Are Studied In The Framework Of Floquet Theory Elucidating The Role Of The Driving Frequency. The Impact Of The Interatomic Repulsive Interactions Is Examined In Detail …
A College Level Geology Field Trip In Western Connecticut And Vicinity, Stanley Schleifer, Nazrul I. Khandaker, Keshaw Narine, Ezazul Haque, Ratan Dhar
A College Level Geology Field Trip In Western Connecticut And Vicinity, Stanley Schleifer, Nazrul I. Khandaker, Keshaw Narine, Ezazul Haque, Ratan Dhar
Publications and Research
There are a number of excellent locations for field exposure for college students in, and around Western Connecticut. These are accessible for a one day field trip within striking distance of New York City, Bridgeport and New Haven, CT and other nearby locations. They are also suitable for an expanded weekend field trip. The field locations include; Kent Falls State Park, Kent, CT, Dinosaur State Park, Rocky Hill, CT, the Hubbard Mining Museum, Kent, CT, Bash Bish Falls in Mt. Washington, Massachusetts, Macedonia Brook State Park in Kent, CT and various outcrops exposed along U. S. Route 7 north of …
Neither Dust Nor Black Carbon Causing Apparent Albedo Decline In Greenland's Dry Snow Zone: Implications For Modis C5 Surface Reflectance, Chris Polashenski, Jack E. Dibb, Mark G. Flanner, Justin Y. Chen, Zoe R. Courville, Alexandra M. Lai, James J. Schauer, Martin M. Shafer, Mike Bergin
Neither Dust Nor Black Carbon Causing Apparent Albedo Decline In Greenland's Dry Snow Zone: Implications For Modis C5 Surface Reflectance, Chris Polashenski, Jack E. Dibb, Mark G. Flanner, Justin Y. Chen, Zoe R. Courville, Alexandra M. Lai, James J. Schauer, Martin M. Shafer, Mike Bergin
Earth Sciences
Remote sensing observations suggest Greenland ice sheet (GrIS) albedo has declined since 2001, even in the dry snow zone. We seek to explain the apparent dry snow albedo decline. We analyze samples representing 2012–2014 snowfall across NW Greenland for black carbon and dust light-absorbing impurities (LAI) and model their impacts on snow albedo. Albedo reductions due to LAI are small, averaging 0.003, with episodic enhancements resulting in reductions of 0.01–0.02. No significant increase in black carbon or dust concentrations relative to recent decades is found. Enhanced deposition of LAI is not, therefore, causing significant dry snow albedo reduction or driving …
In Situ Studies Of Limestone Dissolution In A Coastal Submarine Spring, Rachel Marie Schweers
In Situ Studies Of Limestone Dissolution In A Coastal Submarine Spring, Rachel Marie Schweers
USF Tampa Graduate Theses and Dissertations
Limestone dissolution in karst environments is likely due to geochemistry of the water, the actions of microbial communities, and the effect of water flow. We explored the rate of limestone dissolution and will examine here the microbial communities associated with the limestone. A conduit within the brackish cave, Double Keyhole Spring, on the coast of central west Florida was the site of the experiment. PVC pipes (5cm x 16cm) were filled with crushed limestone that was screened to a 1.9cm – 2.54cm size range. There were three treatments (5 replicates each): Control - sealed autoclaved controls with limestone and conduit …
Hohenberg-Kohn Theorems In Electrostatic And Uniform Magnetostatic Fields, Xiao-Yin Pan, Viraht Sahni
Hohenberg-Kohn Theorems In Electrostatic And Uniform Magnetostatic Fields, Xiao-Yin Pan, Viraht Sahni
Publications and Research
The Hohenberg-Kohn (HK) theorems of bijectivity between the external scalar potential and the gauge invariant nondegenerate ground state density, and the consequent Euler variational principle for the density, are proved for arbitrary electrostatic field and the constraint of fixed electron number. The HK theorems are generalized for spinless electrons to the added presence of an external uniform magnetostatic field by introducing the new constraint of fixed canonical orbital angular momentum. Thereby, a bijective relationship between the external scalar and vector potentials, and the gauge invariant nondegenerate ground state density and physical current density, is proved. A corresponding Euler variational principle …
A Utility-Driven Approach To Supplier Evaluation And Selection: Empirical Validation Of An Integrated Solution Framework, Alptekin Ulutas, Nagesh Shukla, Senevi Kiridena, Peter Gibson
A Utility-Driven Approach To Supplier Evaluation And Selection: Empirical Validation Of An Integrated Solution Framework, Alptekin Ulutas, Nagesh Shukla, Senevi Kiridena, Peter Gibson
Nagesh Shukla
Supplier evaluation and selection (SES) problems have long been studied, leading to the development of a wide range of individual and hybrid models for solving them. However, the lack of widespread diffusion of existing SES models in the industry points to a need for simpler models that can systematically evaluate both qualitative and quantitative attributes of potential suppliers while enhancing the flexibility decision-makers need to account for relevant situational factors. Furthermore, empirical validations of existing models in SES have been few and far between. With a view to addressing these issues, this paper proposes an integrated solution framework that can …
Pathway Variation Analysis (Pva): Modelling And Simulations, Nagesh Shukla, Sudi Lahiri, Darek Ceglarek
Pathway Variation Analysis (Pva): Modelling And Simulations, Nagesh Shukla, Sudi Lahiri, Darek Ceglarek
Nagesh Shukla
Maintaining a care pathway within a hospital to provide complex care to patients is associated with challenges related to variations from the pathway. This occurs due to ineffective decision-making processes, unclear process steps, the interactions, conflicting performance measures for speciality units, and the availability of resources. These variations from the care pathway or standard care delivery processes lead to longer patient waiting times and lower patient throughput. Traditional approaches to improve the pathway focus primarily on reducing variations within the care pathway such as bottlenecks or throughput within the pathway rather than examining variations from the care pathway. In this …
An Approach To Plan And Evaluate The Location Of Radiotherapy Services And Its Application In The New South Wales, Australia, Nagesh Shukla, Rohan Wickramasuriya, Andrew Alexis Miller, Pascal Perez
An Approach To Plan And Evaluate The Location Of Radiotherapy Services And Its Application In The New South Wales, Australia, Nagesh Shukla, Rohan Wickramasuriya, Andrew Alexis Miller, Pascal Perez
Nagesh Shukla
No abstract provided.
Characterization Of Physical, Thermal And Spectroscopic Properties Of Biofield Energy Treated P-Phenylenediamine And P-Toluidine, Mahendra Kumar Trivedi, Alice Branton, Dahryn Trivedi, Gopal Nayak, Ragini Singh, Snehasis Jana
Characterization Of Physical, Thermal And Spectroscopic Properties Of Biofield Energy Treated P-Phenylenediamine And P-Toluidine, Mahendra Kumar Trivedi, Alice Branton, Dahryn Trivedi, Gopal Nayak, Ragini Singh, Snehasis Jana
Mahendra Kumar Trivedi
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
Vladimir Benin
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 for the rotamer interconversion: TSsyn and TSanti, …
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
Vladimir Benin
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.
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
Vladimir Benin
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 2.37 Å. DFT calculations on …
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
Vladimir Benin
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.
Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin
Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin
Vladimir Benin
The current article reports theoretical studies (DFT: B3LYP/6-31+G(d)) on the structure and alkylation reactions of the anions of some secondary N-nitrosocarbamates, a class of ambident nucleophiles whose chemistry has been little explored. Several anions (1–4), with an increasing size of the carbamate alkyl (aryl) group were investigated, in an attempt to establish the influence of the size of that group on the thermal stability and regioselectivity of alkylation of the title anions. The conclusion is that thermal stability and the mode of reaction are affected significantly only in the presence of very large and branched carbamate groups. The thermal decomposition …
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
Vladimir Benin
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.
Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin
Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin
Vladimir Benin
We report in detail the preparation of two substituted terephthalic acids: 2‐sulfomethylterephthalic acid (1) and 2‐phosphonoterephthalic acid (2). Efficient, short syntheses have been developed for both compounds. They are potentially useful monomers for construction of acid‐pendant polymer chains.
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
Vladimir Benin
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 attributed the …
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
Vladimir Benin
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 …
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
Vladimir Benin
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 …
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
Vladimir Benin
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 …
Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin
Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin
Vladimir Benin
We are presenting the preparation, characterization and density functional theory (DFT) studies {B3LYP/6-31+G(d)) of several reiated classes of N-nitrosocarbamates and N-nitrosoureas. The iong-range goal is the design and preparation of compounds, which would undergo photochemical or hydrolytic decomposition, to yield stabilized cyclic cations that can serve as alkylating agents at various nucleophilic centers, including DNA bases.
Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin
Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin
Vladimir Benin
The present report describes the preparation and characterization of several N-2-(trimethylsilyl)ethyl-N-nitrosocarbamates, designed as precursors to thermally unstable secondary N-nitrosocarbamate anions via fluoride-assisted cleavage. X-ray structural studies demonstrate that the core N-nitrosocarbamate moiety has a nearly planar geometry, with an s-E orientation at the N–N bond. DFT calculations (B3LYP/6-31+G(d)) reproduce accurately the structural features of the title compounds and detailed conformational analysis at the same level of theory addresses the long-standing issue of preferred geometries for three classes of related structures: N-nitrosocarbamates, N-nitrosoureas and N-nitrosoamides. Desilylation studies demonstrate that both the …
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
Vladimir Benin
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 …
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
Vladimir Benin
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; 2) C-halogenation viaintermediate N-halogenation, and 3) C-halogenation following an addition …