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Full-Text Articles in Chemistry
Synthetic Studies Directed Toward Streptenol D: Enantioselective Preparation Of The 3,5-Diacetoxy-6E,8E-Decadiene Segment, Bireshwar Dasgupta, William Donaldson
Synthetic Studies Directed Toward Streptenol D: Enantioselective Preparation Of The 3,5-Diacetoxy-6E,8E-Decadiene Segment, Bireshwar Dasgupta, William Donaldson
Chemistry Faculty Research and Publications
The enantioselective preparation of 2-(3′R,5′R-diacetoxy-6E,8E-decadienyl)-1,3-dioxane, (+)-13, is described. This synthesis of the skeleton of streptenol D utilizes the ability of a diene-complexed (tricarbonyl)iron unit to serve as a protecting and stereodirecting functionality.
Tga–Fti.R. Investigation Of The Thermal Degradation Of Nafion® And Nafion®/[Silicon Oxide]-Based Nanocomposites, Q. Deng, Charles Wilkie, R. B. Moore, Kenneth A. Mauritz
Tga–Fti.R. Investigation Of The Thermal Degradation Of Nafion® And Nafion®/[Silicon Oxide]-Based Nanocomposites, Q. Deng, Charles Wilkie, R. B. Moore, Kenneth A. Mauritz
Chemistry Faculty Research and Publications
The integrated TGA–FTi.r. technique probed the thermal degradation of: (1) a Nafion®–H+ membrane; (2) this membrane as modified by incorporation of a SiO2[1-x/4] (OH)x phase via in situ sol–gel reactions for tetraethoxysilane; and (3) this modified membrane as further modified, organically, via post-reaction with diethoxydimethylsilane. Gravimetric loss is multistep for (1) and (2), but occurs in a single step for (3) which has the greatest thermal degradative stability. The considerable inhibition of SO2 evolution for (2) and (3) is rationalized in terms of side-chains that are immobilized within silicon oxide cages …
Direct Voltammetric Observation Of Redox Driven Changes In Axial Coordination And Intramolecular Rearrangement Of The Phenylalanine-82-Histidine Variant Of Yeast Iso-1-Cytochrome C, Benjamin A. Feinberg, Xiangjun Liu, Michael D. Ryan, Abel Schejter, Chongyao Zhang, Emanuel Margoliash
Direct Voltammetric Observation Of Redox Driven Changes In Axial Coordination And Intramolecular Rearrangement Of The Phenylalanine-82-Histidine Variant Of Yeast Iso-1-Cytochrome C, Benjamin A. Feinberg, Xiangjun Liu, Michael D. Ryan, Abel Schejter, Chongyao Zhang, Emanuel Margoliash
Chemistry Faculty Research and Publications
Direct square-wave and cyclic voltammetric electrochemical examination of the yeast iso-1-cytochrome c Phe82His/Cys102Ser variant revealed the intricacies of redox driven changes in axial coordination, concomitant with intramolecular rearrangement. Electrochemical methods are ideally suited for such a redox study, since they provide a direct and quantitative visualization of specific dynamic events. For the iso-1-cytochrome c Phe82His/Cys102Ser variant, square-wave voltammetry showed that the primary species in the reduced state is the Met80-Fe2+-His18 coordination form, while in the oxidized state the His82-Fe3+-His18 form predominates. The addition or removal of an electron to the …
Synthesis And Characterization Of Large Stereoregular Organosiloxane Cycles, O. I. Schchegolikhina, V. A. Igonin, Yulia A. Molodtsova, Yu. A. Pozdniakova, Alexandr A. Zhdanov, T. V. Strelkova, Sergey V. Lindeman
Synthesis And Characterization Of Large Stereoregular Organosiloxane Cycles, O. I. Schchegolikhina, V. A. Igonin, Yulia A. Molodtsova, Yu. A. Pozdniakova, Alexandr A. Zhdanov, T. V. Strelkova, Sergey V. Lindeman
Chemistry Faculty Research and Publications
The large stereoregular phenyltrimethylsiloxysiloxane macrocycles of general formula [PhSi(OSiMe3)O]n (n=6 and 12) have been selectively obtained with high yields by trimethylsilylation of cage-like oligophenylmetallasiloxanes (OPMS) which we described earlier. The compounds 3 (n=6) and 4 (n=12) have been characterized by NMR-spectroscopy method and by single crystal X-ray analysis. This investigation showed unambiguously that the siloxane macrocycles keep their size and configuration (the same as in the initial OPMS) during the trimethylsilylation. Thus a synthetic route for obtaining large stereoregular siloxane macrocycles has been developed.
Folding Under Inequilibrium Conditions As A Possible Reason For Partial Irreversibility Of Heat-Denatured Proteins: Computer Simulation Study, Sergey A. Potekhin, Evgueni Kovriguine
Folding Under Inequilibrium Conditions As A Possible Reason For Partial Irreversibility Of Heat-Denatured Proteins: Computer Simulation Study, Sergey A. Potekhin, Evgueni Kovriguine
Chemistry Faculty Research and Publications
Using computer simulations we have studied possible effects of heating and cooling at different scan rates on unfolding and refolding of macromolecules. We have shown that even the simplest two-state reversible transition can behave irreversibly when an unfavorable combination of cooling rate, relaxation time and activation energy of refolding occurs. On the basis of this finding we suppose that apparent irreversibility of some proteins denatured by heat may result from slow relaxation on cooling rather than thermodynamic instability and/or irreversible alterations of the polypeptide chain. Using this kinetic reversible two-state model, we estimated the effects of the scan rate and …
Graft Copolymerization Of Methacrylic Acid, Acrylic Acid And Methyl Acrylate Onto Styrene–Butadiene Block Copolymer, David D. Jiang, Charles Wilkie
Graft Copolymerization Of Methacrylic Acid, Acrylic Acid And Methyl Acrylate Onto Styrene–Butadiene Block Copolymer, David D. Jiang, Charles Wilkie
Chemistry Faculty Research and Publications
Methyl acrylate, methacrylic acid, and acrylic acid have been graft copolymerized onto styrene–butadiene block copolymer. All three monomers react through the macroradical interacting with the double bond of butadiene. The site of reaction has been established by infrared spectroscopy. For methyl acrylate every unit of the styrene–butadiene block copolymer is grafted but only a small fraction is grafted when the acids are used. The difference apparently lies in the fact that the reaction with the ester is homogeneous while with the acids the reactions are heterogeneous.
Structure Of 5-Nitro-2-Tosylaminobenzaldehyde Di(Morpholin-4-Yl)Aminal Complex With Carbon Tetrachloride, V. N. Khrustalev, Sergey V. Lindeman, L. Yu Ukhin, G. I. Orlova, T. N. Gribanova, O. V. Shishkin
Structure Of 5-Nitro-2-Tosylaminobenzaldehyde Di(Morpholin-4-Yl)Aminal Complex With Carbon Tetrachloride, V. N. Khrustalev, Sergey V. Lindeman, L. Yu Ukhin, G. I. Orlova, T. N. Gribanova, O. V. Shishkin
Chemistry Faculty Research and Publications
The 5-nitro-2-tosylaminobenzaldehyde di(morpholin-4-yl)aminal forms a stable complex with carbon tetrachloride in the crystal phase. X-ray structural study of this complex indicates an essentially shortened intermolecular contact of 2.89 Å between the oxygen atom of the nitro group and one of the chlorine atom of the CCI4 molecule. Quantum-chemical calculations by semiempirical AMI method showed that the formation of such complex did not cause considerable decrease of system energy or change of charge distribution in molecules. It was supposed that this associate has van der Waals character.
Chemical And Electrochemical Studies Of Cl2Fes2Ms2Fecl2N- Clusters [M = Mo (N = 2), W (N = 2), V (N = 3)], Yanming Liu, Jinhai Chen, Michael D. Ryan
Chemical And Electrochemical Studies Of Cl2Fes2Ms2Fecl2N- Clusters [M = Mo (N = 2), W (N = 2), V (N = 3)], Yanming Liu, Jinhai Chen, Michael D. Ryan
Chemistry Faculty Research and Publications
The electrochemistry and spectroelectrochemistry of [Cl2FeS2MS2FeCl2]n- clusters (where n = 2 for M = Mo and W and n = 3 for M = V; Ia, Ib, and Ic, respectively) and the dimetal complex [Cl2FeS2MoS2]2- (IIIa) were examined in order to characterize the structures and properties of the one-electron-reduced complexes. A stable reduction product for Ia was observed spectroelectrochemically at −1.05 V, which could be oxidized back to the starting complex. Reduction at more negative potentials caused …
Studies On The Preparation Of Protomycinolide Iv: Enantioselective Synthesis Of The C3–C9 Segment, James Thomas Wasicak, William Donaldson
Studies On The Preparation Of Protomycinolide Iv: Enantioselective Synthesis Of The C3–C9 Segment, James Thomas Wasicak, William Donaldson
Chemistry Faculty Research and Publications
The C3–C9 segment, (−)-16, of the polyene macrolide antibiotic protomycinolide IV (1a) was prepared in optically pure form from commercially available methyl (S)-2-methyl-3-hydroxypropionate in 12 steps giving 17% yield.
The CuA Center Of A Soluble Domain From Thermus Cytochrome Ba3. An Nmr Investigation Of The Paramagnetic Protein. A Proton Nmr Study Of The Paramagnetic Active Site Of The CuA Variant Of Amicyanin, Richard C. Holz
Chemistry Faculty Research and Publications
No abstract provided.
Preparation And Structures Of Crystalline Aromatic Cation-Radical Salts. Triethyloxonium Hexachloroantimonate As A Novel (One-Electron) Oxidant, Rajendra Rathore, A. S. Kumar, Sergey V. Lindeman, Jay K. Kochi
Preparation And Structures Of Crystalline Aromatic Cation-Radical Salts. Triethyloxonium Hexachloroantimonate As A Novel (One-Electron) Oxidant, Rajendra Rathore, A. S. Kumar, Sergey V. Lindeman, Jay K. Kochi
Chemistry Faculty Research and Publications
Triethyloxonium hexachloroantimonate [Et3O+SbCl6-] is a selective oxidant of aromatic donors (ArH), and it allows the facile preparation and isolation of crystalline paramagnetic salts [ArH+•, SbCl6-] for the X-ray structure determination of various aromatic cation radicals. The mechanistic relationship between the Meerwein salt [Et3O+SbCl6-] and the pure Lewis acid oxidant SbCl5 is based on a prior ethyl transfer from oxygen to chlorine within the ion pair.
Photoinduced Coupling Of Acetylenes And Quinone In The Solid State As Preorganized Donor−Acceptor Pairs, E. Bosch, S. M. Hubig, Sergey V. Lindeman, Jay K. Kochi
Photoinduced Coupling Of Acetylenes And Quinone In The Solid State As Preorganized Donor−Acceptor Pairs, E. Bosch, S. M. Hubig, Sergey V. Lindeman, Jay K. Kochi
Chemistry Faculty Research and Publications
Crystalline electron donor−acceptor (EDA) complexes of various diarylacetylenes (DA) and dichlorobenzoquinone (DB) are isolated and structurally characterized by X-ray crystallography. Deliberate excitation of either the DB acceptor at λDB = 355 nm or the 1:2 [DA, 2DB] complex at λCT = 532 nm in the solid state leads to [2 + 2] cycloaddition and identical (isomeric) mixtures of the quinone methide products. Time-resolved (ps) diffuse reflectance spectroscopy identifies the ion-radical pair [DA•+, DB•-] as the reactive intermediate derived by photoinduced electron transfer in both photochemical …
Disproportionation And Structural Changes Of Tetraarylethylene Donors Upon Successive Oxidation To Cation Radicals And To Dications, Rajendra Rathore, Sergey V. Lindeman, A. S. Kumar, Jay K. Kochi
Disproportionation And Structural Changes Of Tetraarylethylene Donors Upon Successive Oxidation To Cation Radicals And To Dications, Rajendra Rathore, Sergey V. Lindeman, A. S. Kumar, Jay K. Kochi
Chemistry Faculty Research and Publications
The stepwise (one-electron) chemical oxidation of the tetraphenylethylene donor and its substituted analogues (D) can be carried out by electron exchange with aromatic cations or antimony(V) oxidants to selectively afford the cation radical (D+•) initially and then the dication (D2+). The ready interchange of the latter establishes the facile disproportionation (i.e., 2D+• ⇌ D2+ + D) that was originally examined by only transient electrochemical techniques. The successful isolations of the crystalline salts of the tetraanisylethylene cation radical (1+•) as well as the …