Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Other Chemistry (42)
- Analytical Chemistry (24)
- Biochemical Phenomena, Metabolism, and Nutrition (23)
- Chemical and Pharmacologic Phenomena (23)
- Environmental Chemistry (23)
-
- Inorganic Chemistry (23)
- Materials Chemistry (23)
- Medical Biochemistry (23)
- Medical Sciences (23)
- Medicinal-Pharmaceutical Chemistry (23)
- Medicine and Health Sciences (23)
- Organic Chemistry (23)
- Arts and Humanities (1)
- Atomic, Molecular and Optical Physics (1)
- Computational Chemistry (1)
- Computer Sciences (1)
- History (1)
- Numerical Analysis and Scientific Computing (1)
- Physics (1)
- Quantum Physics (1)
- Publication Year
Articles 31 - 44 of 44
Full-Text Articles in Physical Chemistry
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 …
Biophysical Characterization Of A Beta-Peptide Bundle: Comparison To Natural Proteins, E. James Petersson, Cody J. Craig, Douglas S. Daniels, Jade X. Qiu, Alanna S. Schepartz
Biophysical Characterization Of A Beta-Peptide Bundle: Comparison To Natural Proteins, E. James Petersson, Cody J. Craig, Douglas S. Daniels, Jade X. Qiu, Alanna S. Schepartz
Chemistry Faculty Publications
We recently described the high-resolution X-ray structure of a helical bundle composed of eight copies of the β-peptide Zwit-1F. Like many proteins in Nature, the Zwit-1F octamer contains parallel and antiparallel helices, extensive inter-helical electrostatic interactions, and a solvent-excluded hydrophobic core. Here we explore the stability of the Zwit-1F octamer using circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AU), differential scanning calorimetry (DSC), and NMR. These studies demonstrate that the thermodynamic and kinetic properties of Zwit-1F closely resemble those of α-helical bundle proteins. Together these studies should provide a model for the design of β-peptide proteins with biological functions.
High-Resolution Structure Of A Beta-Peptide Bundle, Douglas S. Daniels, E. James Petersson, Jade X. Qiu, Alanna S. Schepartz
High-Resolution Structure Of A Beta-Peptide Bundle, Douglas S. Daniels, E. James Petersson, Jade X. Qiu, Alanna S. Schepartz
Chemistry Faculty Publications
We recently reported that β-peptides can form discrete hetero-oligomers in aqueous solution. Here we describe the structure of such an oligomer as determined by X-ray crystallography. The structure of Zwit-1F reveals a homo-octamer of two cupped “hands” composed of both parallel and antiparallel 314-helices. The core of the assembly is composed entirely of solvent-excluded β3-homoleucine residues. The Zwit-1F assembly shares many of the physical characteristics of natural proteins.
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
Chemistry Faculty Publications
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 …
Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin
Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin
Chemistry Faculty Publications
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.
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
Chemistry Faculty Publications
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
Chemistry Faculty Publications
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 …
Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels
Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels
Chemistry Faculty Publications
Formal education has removed itself so far from any truly integrated view of the Natural World that fragmentation and certainty are prevailing ethics. Technological progress has resulted in increased specialization within academic disciplines and their concurrent separation from each other. Knowledge is extracted from a fully integrated world, but is examined and defined by the 'dis-integrated' objectives.
The Role Of Written And Verbal Expression In Improving Communication Skills For Students In An Undergraduate Chemistry Program, Brian P. Coppola, Douglas S. Daniels
The Role Of Written And Verbal Expression In Improving Communication Skills For Students In An Undergraduate Chemistry Program, Brian P. Coppola, Douglas S. Daniels
Chemistry Faculty Publications
Proofreading, editing, and critique, the customary assessment tools scientists use to evaluate professional journal articles, grant applications, and any other writing, can be applied equally well in introductory science instruction. Such feedback is, in fact, crucial to growth and development. When learning anything new, students and faculty alike rely heavily on sources other than themselves (‘external editors’) to assess their understanding as they develop self-assessment skills (or ‘internal editors’). Although they rarely describe it in these terms, faculty nonetheless assume that students have developed and refined their internal skills by the time they take examinations and write term papers. Unfortunately, …
Nonlinear Optical Properties Of Bacteriorhodopsin: Assignment Of The Third-Order Polarizability Based On Two-Photon Absorption Spectroscopy, Robert R. Birge, Mark Masthay, Jeffery A. Stuart, Jack R. Tallent, Chian-Fan Zhang
Nonlinear Optical Properties Of Bacteriorhodopsin: Assignment Of The Third-Order Polarizability Based On Two-Photon Absorption Spectroscopy, Robert R. Birge, Mark Masthay, Jeffery A. Stuart, Jack R. Tallent, Chian-Fan Zhang
Chemistry Faculty Publications
The third-order (pi) -electron polarizability, (gamma) (pi), of bacteriorhodopsin in the 0.0 - 1.2 eV optical region is assigned based on an analysis of the experimental two-photon properties of the low-lying singlet state manifold. The following selected values of (gamma) (pi) (units of 10-36 esu) are observed: (gamma) (0;0,0,0) equals 2482 +/- 327; (gamma) (-3(omega) ;(omega) ,(omega) ,(omega) ) equals 2976 +/- 385 ((omega) equals 0.25 eV), 5867 +/- 704 ((omega) = 0.5 eV), 14863 +/- 1614 ((omega) = 0.66 eV), 15817 +/- 2314 ((omega) equals 1.0 eV), 10755 +/- 1733 ((omega) equals 1.17 eV). The third-order polarizability of this …
Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang
Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang
Chemistry Faculty Publications
Experimental and theoretical evidence is presented which suggests that two distinct forms of light-adapted bacteriorhodopsin may exist. We propose that these two forms have characteristic photocycles with significantly different primary quantum yields. INDO-PSDCI molecular orbital procedures and semiempirical molecular dynamics simulations predict that one ground state geometry of bR undergoes photochemistry with a primary quantum yield, Φ1, of ~ 0.27, and that a second ground state geometry, with a slightly displaced counterion, yields Φ1 ~ 0.74. This theoretical model is supported by the observation that literature measurements of Φ1 tend to fall into one of two categories- those that observe …
Friedrich Wöhler, John Alfred Heitmann
Friedrich Wöhler, John Alfred Heitmann
History Faculty Publications
Friedrich Wöhler synthesized urea in 1828 and thus first demonstrated that organic materials, heretofore believed to possess a vital force, need not be made exclusively within living organisms. He also isolated aluminum metal in 1827 and discovered the elements beryllium and yttrium.
A Theoretical Investigation Of The One– And Two–Photon Properties Of Porphyrins, Mark Masthay, Leonore A. Findsen, Brian M. Pierce, David F. Bocian, James S. Lindsey, Robert R. Birge
A Theoretical Investigation Of The One– And Two–Photon Properties Of Porphyrins, Mark Masthay, Leonore A. Findsen, Brian M. Pierce, David F. Bocian, James S. Lindsey, Robert R. Birge
Chemistry Faculty Publications
The one‐ and two‐photon properties of free base porphin, free base porphin dianion, and the 2,4‐substituted diformyl and divinyl analogs of these molecules are studied using a semiempirical SCF‐MO formalism (CNDO‐π‐SCF‐MO‐PSDCI) including extensive single and double configuration interaction. Strongly two‐photon allowed states are predicted to lie in the Soret region as well as in the region between the Soret and visible bands. A number of the two‐photon allowed states in the Soret region are predicted to have two‐photon absorptivities exceeding 100×10−50 cm4 s molecule−1 photon−1. The calculations indicate that the visible (Q) states are well characterized by the …