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2007

Chemistry Publications

Articles 1 - 10 of 10

Full-Text Articles in Physical Sciences and Mathematics

Total Synthesis Of (+/-)-Goniomitine Via A Formal Nitrile/Donor-Acceptor Cyclopropane [3 + 2] Cyclization., Christian L Morales, Brian L Pagenkopf Dec 2007

Total Synthesis Of (+/-)-Goniomitine Via A Formal Nitrile/Donor-Acceptor Cyclopropane [3 + 2] Cyclization., Christian L Morales, Brian L Pagenkopf

Chemistry Publications

The total synthesis of (+/-)-goniomitine has been accomplished in 17 linear steps with 5.2% overall yield starting from commercially available delta-valerolactam. A synthetic highlight includes the first application of a formal [3 + 2] cycloaddition between a highly functionalized nitrile and a donor-acceptor cyclopropane to prepare an indole nucleus. The use of a microwave reactor is shown to greatly improve the reaction times for two steps.

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Reduction Of Esters To Ethers Utilizing The Powerful Lewis Acid Bf2otf·Oet2, Brian Pagenkopf, Nicholas A. Morra Sep 2007

Reduction Of Esters To Ethers Utilizing The Powerful Lewis Acid Bf2otf·Oet2, Brian Pagenkopf, Nicholas A. Morra

Chemistry Publications

No abstract provided.

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First Total Synthesis And Structural Reassignment Of (-)-Aplysiallene., Jian Wang, Brian L Pagenkopf Aug 2007

First Total Synthesis And Structural Reassignment Of (-)-Aplysiallene., Jian Wang, Brian L Pagenkopf

Chemistry Publications

The first total synthesis of (-)-aplysiallene has been completed in 16 steps and features a key sequential Mukaiyama aerobic oxidative cyclization to prepare the fused bis-THF core. The original stereochemical assignment has been revised as shown.

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C-2/C-3 Annulation And C-2 Alkylation Of Indoles With 2-Alkoxycyclopropanoate Esters., Barbora Bajtos, Ming Yu, Hongda Zhao, Brian L Pagenkopf Aug 2007

C-2/C-3 Annulation And C-2 Alkylation Of Indoles With 2-Alkoxycyclopropanoate Esters., Barbora Bajtos, Ming Yu, Hongda Zhao, Brian L Pagenkopf

Chemistry Publications

The annulation reaction between various indoles and 2-alkoxycyclopropanoate esters is reported. Both high efficiency and complete stereochemical control were observed in some cases with this annulation process. A single stereocenter on the cyclopropane controls the diastereoselective formation of up to four new stereocenters. A different reaction course was observed with 3-substituted indole substrates, and an intervening C-3 to C-2-migration process arose that gives synthetically useful C-2 alkylation indole products.

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Control Of The Cation Occupancies Of Mnzn Ferrite Synthesized Via Reverse Micelles, M. D. Shultz, M. J. Allsbrook, E. E. Carpenter Jan 2007

Control Of The Cation Occupancies Of Mnzn Ferrite Synthesized Via Reverse Micelles, M. D. Shultz, M. J. Allsbrook, E. E. Carpenter

Chemistry Publications

Variations in cation occupancy in mixed metal ferrite systems can affect their electronic and magnetic properties. It is known that different synthesis parameters can lead to various cation distributions and the ability to tune these distributions is of great interest. This study uses the extended x-ray-absorption fine structure–IR relationship to investigate the effect of various Fe2+/Fe3+ ratios in initial synthesis conditions on cation distribution for manganesezincferrite (MZFO). Differences in the precipitated material before firing could lead to differences in the final material if fired under similar conditions. This work uses several different ratios of Fe3+/Fe2+, which will affect the initial …

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Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe2o4 Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris Jan 2007

Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe2o4 Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris

Chemistry Publications

MnFe2O4nanoparticles with diameters ranging from about 4to50nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe2O4 for various particle sizes were determined by using high temperature magnetometry. The ∼4nm MnFe2O4 particles showed a TN of about 320°C whereas the ∼50nm particles had a TN of about 400°C. The high Néel temperature, compared with the bulk MnFe2O4 TN of 300°C, is …

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Vapor Phase Nucleation On Neutral And Charged Nanoparticles: Condensation Of Supersaturated Trifluoroethanol On Mg Nanoparticles, Victor Abdelsayed, M. Samy El-Shall Jan 2007

Vapor Phase Nucleation On Neutral And Charged Nanoparticles: Condensation Of Supersaturated Trifluoroethanol On Mg Nanoparticles, Victor Abdelsayed, M. Samy El-Shall

Chemistry Publications

A new technique is described to study the condensation of supersaturated vapors on nanoparticles under well-defined conditions of vapor supersaturation, temperature, and carrier gas pressure. The method is applied to the condensation of supersaturated trifluoroethanol (TFE) vapor on Mg nanoparticles. The nanoparticles can be activated to act as condensation nuclei at supersaturations significantly lower than those required for homogeneous nucleation. The number of activated nanoparticles increases with increasing the vapor supersaturation. The small difference observed in the number of droplets formed on positively and negatively charged nanoparticles is attributed to the difference in the mobilities of these nanoparticles. Therefore, no …

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Investigations On The Structure Of Dimethyl Sulfoxide And Acetone In Aqueous Solution, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar Jan 2007

Investigations On The Structure Of Dimethyl Sulfoxide And Acetone In Aqueous Solution, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar

Chemistry Publications

Aqueous solutions of dimethyl sulfoxide (DMSO) and acetone have been investigated using neutron diffraction augmented with isotopic substitution and empirical potential structure refinement computer simulations. Each solute has been measured at two concentrations—1:20 and 1:2 solute:water mole ratios. At both concentrations for each solute, the tetrahedral hydrogen bonding network of water is largely unperturbed, though the total water molecule coordination number is reduced in the higher 1:2 concentrations. With higher concentrations of acetone, water tends to segregate into clusters, while in higher concentrations of DMSO the present study reconfirms that the structure of the liquid is dominated by DMSO-water interactions. …

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Effect Of Field Direction On Electrowetting In A Nanopore, D. Bratko, Christopher D. Daub, Kevin Leung, Alenka Luzar Jan 2007

Effect Of Field Direction On Electrowetting In A Nanopore, D. Bratko, Christopher D. Daub, Kevin Leung, Alenka Luzar

Chemistry Publications

We manifest a significant influence of field direction and polarity on surface wetting, when the latter is tuned by application of an external electric field. Thermodynamics of field-induced filling of hydrocarbon-like nanopores with water is studied by open ensemble molecular simulation. Increased field strength consistently results in water-filling and electrostriction in hydrophobic nanopores. A threshold field commensurate with surface charge density of about one elementary charge per 10 nm2 suffices to render prototypical paraffin surfaces hydrophilic. When a field is applied in the direction perpendicular to the confining walls, the competition between orientational polarization and angle preferences of interfacial water …

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Electrowetting At The Nanoscale, C. D. Daub, D. Bratko, K. Leung, A. Luzar Jan 2007

Electrowetting At The Nanoscale, C. D. Daub, D. Bratko, K. Leung, A. Luzar

Chemistry Publications

Using molecular simulations of nano-sized aqueous droplets on a model graphite surface we demonstrate remarkable sensitivity of water contact angles to the applied electric field polarity and direction relative to the liquid/solid interface. The effect is explained by analyzing the influence of the field on interfacial hydrogen bonding in the nanodrop, which in turn affects the interfacial tensions. The observed anisotropy in droplet wetting is a new nanoscale phenomenon that has so far been elusive as, in current experimental setups, surface molecules represent a very low fraction of the total number affected by the field. Our findings may have important …

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