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Chemistry Publications

Chemistry

2014

Articles 1 - 11 of 11

Full-Text Articles in Physical Sciences and Mathematics

Resin-Supported Arylstannanes As Precursors For Radiolabeling With Iodine: Benzaldehydes, Benzoic Acids, Benzamides, And Nhs Esters, Mustafa Janabi, Catherine M. Pollock, Ann-Marie Chacko, Duncan H. Hunter Sep 2014

Resin-Supported Arylstannanes As Precursors For Radiolabeling With Iodine: Benzaldehydes, Benzoic Acids, Benzamides, And Nhs Esters, Mustafa Janabi, Catherine M. Pollock, Ann-Marie Chacko, Duncan H. Hunter

Chemistry Publications

A highly cross-linked polystyrene resin bearing a reactive chlorostannane moiety 1 has been used to generate a variety of arylstannane radiopharmaceutical precursors for no-carrier-added radioiodination. The resins were characterized for their solvent compatibility and sensitivity to acid cleavage. Resin-supported arylstannanes synthesized via their aryl lithium analogues include 3- and 4-stannylbenzaldehydes, 3- and 4-stannylbenzoic acids, and 3- and 4-N-succinimidyl benzoates. A three-step route to the resin-supported stannylbenzoic acids 12a/b was developed through resin-supported benzaldehydes 11a/b. The aldehyde to acid conversion efficiency is >90%, and acid loading capacities of 0.66–0.94 mmol/g were obtained. Resin-supported N-succinimidyl benzoates 16a/b …

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Synthesis Of (+)-Bovidic Acid, Geoffrey A. Phillips, Timothy B. Wright, Andrew C. Stevens, Brian Pagenkopf Aug 2014

Synthesis Of (+)-Bovidic Acid, Geoffrey A. Phillips, Timothy B. Wright, Andrew C. Stevens, Brian Pagenkopf

Chemistry Publications

(+)-Bovidic acid is an 18-carbon hydroxyfuranoid acid isolated from the pelage of the gaur (Bosfrontalis) and displays potential as an insect repellant. Both a formal and total synthesis of (+)-bovidic acid was carried out with the core of the natural product being synthesized through Mukaiyama aerobic oxidative cyclization employing the second-generation Co(nmp)2 catalyst.

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The [4+2] Cycloaddition Of Donor-Acceptor Cyclobutanes And Nitrosoarenes., Naresh Vemula, Andrew C Stevens, Tyler B Schon, Brian L Pagenkopf Feb 2014

The [4+2] Cycloaddition Of Donor-Acceptor Cyclobutanes And Nitrosoarenes., Naresh Vemula, Andrew C Stevens, Tyler B Schon, Brian L Pagenkopf

Chemistry Publications

The Yb(OTf)3 catalyzed [4+2] cycloaddition between donor-acceptor cyclobutanes and nitrosoarenes is disclosed. This method facilitates the synthesis of tetrahydro-1,2-oxazines in good to excellent yields as single diastereomers. Except for a few electron-deficient nitrosoarenes, excellent regioselectivity was observed throughout these studies.

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Enhanced Magnetic Anisotropy In Cobalt-Carbide Nanoparticles, Ahmed A. El-Gendy, Meichun Qian, Zachary J. Huba, Shiv N. Khanna, Everett E. Carpenter Jan 2014

Enhanced Magnetic Anisotropy In Cobalt-Carbide Nanoparticles, Ahmed A. El-Gendy, Meichun Qian, Zachary J. Huba, Shiv N. Khanna, Everett E. Carpenter

Chemistry Publications

An outstanding problem in nano-magnetism is to stabilize the magnetic order in nanoparticles at room temperatures. For ordinary ferromagnetic materials, reduction in size leads to a decrease in the magnetic anisotropy resulting in superparamagnetic relaxations at nanoscopic sizes. In this work, we demonstrate that using wet chemical synthesis, it is possible to stabilize cobalt carbide nanoparticles which have blocking temperatures exceeding 570 K even for particles with magnetic domains of 8 nm. First principles theoretical investigations show that the observed behavior is rooted in the giant magnetocrystalline anisotropies due to controlled mixing between C p- and Co d-states.

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Nanoconfined Water Under Electric Field At Constant Chemical Potential Undergoes Electrostriction, Davide Vanzo, D. Bratko, Alenka Luzar Jan 2014

Nanoconfined Water Under Electric Field At Constant Chemical Potential Undergoes Electrostriction, Davide Vanzo, D. Bratko, Alenka Luzar

Chemistry Publications

Electric control of nanopore permeation by water and solutions enables gating in membrane ion channels and can be exploited for transient surface tuning of rugged substrates, to regulate capillary permeability in nanofluidics, and to facilitate energy absorption in porous hydrophobic media. Studies of capillary effects, enhanced by miniaturization, present experimental challenges in the nanoscale regime thus making molecular simulations an important complement to direct measurement. In a molecular dynamics (MD) simulation, exchange ofwater between the pores and environment requires modeling of coexisting confined and bulk phases, with confined water under the field maintaining equilibrium with the unperturbed environment. In the …

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Unconventional Hydrogen Bonding To Organic Ions In The Gas Phase: Stepwise Association Of Hydrogen Cyanide With The Pyridine And Pyrimidine Radical Cations And Protonated Pyridine, Ahmed M. Hamid, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz Jan 2014

Unconventional Hydrogen Bonding To Organic Ions In The Gas Phase: Stepwise Association Of Hydrogen Cyanide With The Pyridine And Pyrimidine Radical Cations And Protonated Pyridine, Ahmed M. Hamid, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz

Chemistry Publications

Equilibrium thermochemical measurements using the ion mobility drift cell technique have been utilized to investigate the binding energies and entropy changes for the stepwise association of HCN molecules with the pyridine and pyrimidine radical cations forming the C5H5N+· (HCN)nand C4H4N2 +· (HCN)n clusters, respectively, with n = 1–4. For comparison, the binding of 1–4 HCN molecules to the protonated pyridine C5H5NH+(HCN)n has also been investigated. The binding energies of HCN to the pyridine and pyrimidine radical cations are nearly equal (11.4 and 12.0 kcal/mol, respectively) but weaker than the HCN binding to the protonated pyridine (14.0 kcal/mol). …

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Wetting Transparency Of Graphene In Water, J. Driskill, D. Vanzo, D. Bratko, A. Luzar Jan 2014

Wetting Transparency Of Graphene In Water, J. Driskill, D. Vanzo, D. Bratko, A. Luzar

Chemistry Publications

Measurements of contact angle on graphene sheets show a notable dependence on the nature of the underlying substrate, a phenomenon termed wetting transparency. Our molecular modeling studies reveal analogous transparency in case of submerged graphene fragments in water. A combined effect of attractive dispersion forces, angle correlations between aqueous dipoles, and repulsion due to the hydrogen-bond-induced orientation bias in polarized hydration layers acting across graphene sheet, enhances apparent adhesion of water to graphene. We show wetting free energy of a fully wetted graphene platelet to be about 8 mNm−1 lower than for graphene wetted only on one side, which gives …

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Astroecology, Cosmo-Ecology, And The Future Of Life, Michael Noah Mautner Jan 2014

Astroecology, Cosmo-Ecology, And The Future Of Life, Michael Noah Mautner

Chemistry Publications

Astroecology concerns the relations between life and space resources, and cosmo-ecology extrapolates these relations to cosmological scales. Experimental astroecology can quantify the amounts of life that can be derived from space resources. For this purpose, soluble carbon and electrolyte nutrients were measured in asteroid/meteorite materials. Microorganisms and plant cultures were observed to grow on these materials, whose fertilities are similar to productive agricultural soils. Based on measured nutrient contents, the 1022 kg carbonaceous asteroids can yield 1018 kg biomass with N and P as limiting nutrients (compared with the estimated 1015 kg biomass on Earth). These data …

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A Novel Two-Laser Interface For Coupling Capillary Electrochromatography With Ion-Trap Time-Of-Flight Mass Spectrometry, David C. Simpson, Alexander J. Yates, John H. Knox, Pat R.R. Langridge-Smith Jan 2014

A Novel Two-Laser Interface For Coupling Capillary Electrochromatography With Ion-Trap Time-Of-Flight Mass Spectrometry, David C. Simpson, Alexander J. Yates, John H. Knox, Pat R.R. Langridge-Smith

Chemistry Publications

An interface has been developed for the hyphenation of capillary electrochromatography (CEC) with mass spectrometry (MS). Chromatographic eluate vaporization and selective analyte ionization occur within a quadrupole ion-trap, which permits significant instrument simplification when compared with the atmospheric pressure interfaces typically used for CEC-MS. Vaporization is achieved using laser desorption at 1064 nm while ionization is accomplished through UV photoionization. This two-step approach, through ionization laser wavelength selection, can provide ultratrace analysis with high selectivity. The mass spectrometer is a hybrid ion-trap time-of-flight (TOF) instrument in which the ion-trap is used in radio frequency-only mode, with DC-pulse ejection, to provide …

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Proton-Bound Dimers Of Nitrogen Heterocyclic Molecules: Substituent Effects On The Structures And Binding Energies Of Homodimers Of Diazine, Triazine, And Fluoropyridine, Isaac K. Attah, Sean P. Platt, Michael Mautner, M. S. El-Shall, Saadullah G. Aziz, Abdulrahman O. Alyoubi Jan 2014

Proton-Bound Dimers Of Nitrogen Heterocyclic Molecules: Substituent Effects On The Structures And Binding Energies Of Homodimers Of Diazine, Triazine, And Fluoropyridine, Isaac K. Attah, Sean P. Platt, Michael Mautner, M. S. El-Shall, Saadullah G. Aziz, Abdulrahman O. Alyoubi

Chemistry Publications

The bonding energies of proton-bound homodimers BH+B were measured by ion mobilityequilibrium studies and calculated at the DFT B3LYP/6-311++G* * level, for a series of nitrogen heterocyclic molecules (B) with electron-withdrawing in-ring N and on-ring F substituents. The binding energies (ΔH°dissoc) of the proton-bound dimers (BH+B) vary significantly, from 29.7 to 18.1 kcal/mol, decreasing linearly with decreasing the proton affinity of the monomer (B). This trend differs significantly from the constant binding energies of most homodimers of other organic nitrogen and oxygen bases. The experimentally measured ΔH°dissoc for (1,3-diazine)2H+, i.e., (pyrimidine)2H+ and …

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Direct Observation Of Metal Nanoparticles As Heterogeneous Nuclei For The Condensation Of Supersaturated Organic Vapors: Nucleation Of Size-Selected Aluminum Nanoparticles In Acetonitrile And N-Hexane Vapors, Victor Abdelsayed, M. Samy El-Shall Jan 2014

Direct Observation Of Metal Nanoparticles As Heterogeneous Nuclei For The Condensation Of Supersaturated Organic Vapors: Nucleation Of Size-Selected Aluminum Nanoparticles In Acetonitrile And N-Hexane Vapors, Victor Abdelsayed, M. Samy El-Shall

Chemistry Publications

This work reports the direct observation and separation of size-selected aluminum nanoparticlesacting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metalnanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor.Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for theheterogeneous …

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