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Gas-phase Chemistry (gas-phase + chemistry)
Selected AbstractsGas-Phase Chemistry of Vanadium Oxide Cluster Cations VmOn+ (m = 1,4; n = 1,10) with Water and Molecular OxygenEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2008Sandra Feyel Abstract Bare vanadium oxide cluster cations VmOn+ (m = 1,4; n =1,10) generated by electrospray ionization are investigated with respect to their reactivity toward water and molecular oxygen by using mass spectrometric techniques. Besides ion hydration, the ion/molecule reactions of VmOn+ with oxygen-labeled water (H218O) also lead to 16O/18O exchange reactions of the vanadium oxide clusters cations. Although the probability of degenerate 16O/18O exchange between VmOn+ and water is fairly high for the cluster cations with a medium valence state of vanadium, oxygen-atom exchange reactions between VmOn+ and 18O2 can only be accomplished by VO+, V3O6+, and V4O8+. Particularly interesting is the fact that not only oxygen atoms from vanadyl units are exchanged in the cluster cations, but bridging oxygen atoms are also most likely involved in the processes. Other reaction channels for the interaction of VmOn+ cluster cations with molecular oxygen are reported as well, such as oxidative degradation of the low-valent cluster cations upon collision with O2 and formation of association complexes for the high-valent cluster cations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Mass Spectrometry and Gas-Phase Chemistry of Non-Covalent Complexes.ANGEWANDTE CHEMIE, Issue 22 2010Supramolecular Chemistry in the Gas Phase. John Wiley & Sons, Hoboken 2009. 571,S., geb., 99.90,,.,ISBN 978-0470131152 [source] ChemInform Abstract: Gas-Phase Chemistry of Bare V+ Cation with Oxygen and Water at Room Temperature: Formation and Hydration of Vanadium Oxide Cations.CHEMINFORM, Issue 33 2001Gregory K. Koyanagi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Microsolvated and Chelated Butylzinc Cations: Formation, Relative Stability, and Unimolecular Gas-Phase ChemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 46 2009Julia Abstract Solutions of butylzinc iodide in tetrahydrofuran, acetonitrile, and N,N -dimethylformamide were analyzed by electrospray ionization mass spectrometry. In all cases, microsolvated butylzinc cations [ZnBu(solvent)n]+, n=1,3, were detected. The parallel observation of the butylzincate anion [ZnBuI2], suggests that these ions result from disproportionation of neutral butylzinc iodide in solution. In the presence of simple bidentate ligands (1,2-dimethoxyethane, N,N -dimethyl-2-methoxyethylamine, and N,N,N,,N, -tetramethylethylenediamine), chelate complexes of the type [ZnBu(ligand)]+ form quite readily. The relative stabilities of these complexes were probed by competition experiments and analysis of their unimolecular gas-phase reactivity. Fragmentation of mass-selected [ZnBu(ligand)]+ leads to the elimination of butene and formation of [ZnH(ligand)]+. In marked contrast, the microsolvated cations [ZnBu(solvent)n]+ lose the attached solvent molecules upon gas-phase fragmentation to produce bare [ZnBu]+, which subsequently dissociates into [C4H9]+ and Zn. This difference in reactivity resembles the situation in organozinc solution chemistry, in which chelating ligands are needed to activate dialkylzinc compounds for the nucleophilic addition to aldehydes. [source] Studies of the Interesting Gas-phase Rearrangement Reactions of 2-Pyrimidinyloxy- N -arylbenzylurea Promoted by Urea-Carbamimidic Acid Tautomerism by ESI-MS/MS and Theoretical Computation,CHINESE JOURNAL OF CHEMISTRY, Issue 9 2010Chu Xu Abstract The gas-phase rearrangement reactions of compound 1, 2-dimethoxypyrimidinyloxybenzylaminoben- zenedipropylurea, were studied by ESI-MS/MS. The experimental results showed that introduction of dipropylurea moiety into the molecule initiated various interesting gas-phase chemistries and the mechanisms were proposed on the basis of hydrogen/deuterium (H/D) exchange experiments and theoretical computations. Moreover, product 2, the solution-phase rearrangement product of compound 1, was synthesized and its gas-phase chemistries were also studied to support the propos gas-phase rearrangement reactions of compound 1. [source] Importance of O(3P) atoms and OH radicals in hydrocarbon oxidation during the nonthermal plasma treatment of diesel exhaust inferred using relative-rate methods,INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2003John Hoard The consumption of acetylene and propene during passage of simulated diesel exhaust through a nonthermal plasma at 453 K and atmospheric pressure was studied using experimental and computational techniques. Experimental observations of the relative decay rates of acetylene and propene and computer modeling of the chemical and physical processes in the plasma suggest that O(3P) atoms and, to a lesser extent, OH radicals are the dominant species responsible for initiating hydrocarbon oxidation in this system. Results are discussed in terms of the gas-phase chemistry occurring during the nonthermal plasma treatment of diesel exhaust. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 231,238, 2003 [source] Air pollution: A half century of progressAICHE JOURNAL, Issue 6 2004John H. Seinfeld Abstract In the 50 years since the air pollution episodes of Donora, PA and London, U.K., a great deal of progress has been made in understanding the nature and sources of air pollution and the atmospheric transport and transformation of pollutants. Also, many significant technological advances in air pollution control equipment, such as the automobile exhaust gas catalytic converter, have led to effective reduction of emissions from a variety of major pollution sources. Finally, remarkable developments in instrumentation for sampling the trace species in the atmosphere have been and continue to be made. Relatively less progress has been made in understanding the biological mechanisms by which pollutants lead to human injury and mortality. In this review the focus is on the extraordinary progress that has been made over the last half century in understanding the atmospheric nature and behavior of pollutants, both gaseous and particulate. A major breakthrough was the determination of the gas-phase chemistry of both the natural and polluted atmosphere, chemistry that leads to the formation of ozone and a vast array of oxidized molecules. The mechanisms of the oxidation of atmospheric sulfur dioxide, one of the main primary pollutants, were elucidated. Finally, the chemistry, physics, and optics of atmospheric particulate matter (aerosols) have been laid open by many stunning research achievements. Whereas 50 years ago air pollution was thought to be confined to the area around a city, it is now recognized that species emitted on one continent frequently find their way to other continents. Strategies for dealing with a truly global atmospheric backyard now represent a major challenge. © 2004 American Institute of Chemical Engineers AIChE J, 50:1096,1108, 2004 [source] Australia Telescope Compact Array 1.2-cm observations of the massive star-forming region G305.2+0.2MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007Andrew J. Walsh ABSTRACT We report on Australia Telescope Compact Array observations of the massive star-forming region G305.2+0.2 at 1.2 cm. We detected emission in five molecules towards G305A, confirming its hot core nature. We determined a rotational temperature of 26 K for methanol. A non-local thermodynamic equilibrium excitation calculation suggests a kinematic temperature of the order of 200 K. A time-dependent chemical model is also used to model the gas-phase chemistry of the hot core associated with G305A. A comparison with the observations suggest an age of between 2 × 104 and 1.5 × 105 yr. We also report on a feature to the south-east of G305A which may show weak Class I methanol maser emission in the line at 24.933 GHz. The more evolved source G305B does not show emission in any of the line tracers, but strong Class I methanol maser emission at 24.933 GHz is found 3 arcsec to the east. Radio continuum emission at 18.496 GHz is detected towards two H ii regions. The implications of the non-detection of radio continuum emission towards G305A and G305B are also discussed. [source] Role of 2-oxo and 2-thioxo modifications on the proton affinity of histidine and fragmentation reactions of protonated histidine,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2010Adrian K. Y. Lam A combination of electrospray ionisation (ESI), multistage and high-resolution mass spectrometry experiments was used to compare the gas-phase chemistry of the amino acids histidine (1), 2-oxo-histidine (2), and 2-thioxo-histidine (3). Collision-induced dissociation (CID) of all three different proton-bound heterodimers of these amino acids led to the relative gas-phase proton affinity order of: histidine >2-thioxo-histidine >2-oxo-histidine. Density functional theory (DFT) calculations confirm this order, with the lower proton affinities of the oxidised histidine derivatives arising from their ability to adopt the more stable keto/thioketo tautomeric forms. All protonated amino acids predominately fragment via the combined loss of H2O and CO to yield a1 ions. Protonated 2 and 3 also undergo other small molecule losses including NH3 and the imine HN=CHCO2H. The observed differences in the fragmentation pathways are rationalised through DFT calculations, which reveal that while modification of histidine via the introduction of the oxygen atom in 2 or the sulfur atom in 3 does not affect the barriers against the loss of H2O+CO, barriers against the losses of NH3 and HN=CHCO2H are lowered relative to protonated histidine. Copyright © 2010 John Wiley & Sons, Ltd. [source] Cu[Al(ORF)4] Starting Materials and their Application in the Preparation of [Cu(Sn)]+ (n=12, 8) ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2009Gustavo Santiso-Quiñones Dr. Abstract Naked copper,? A newly developed simple two-step route to weakly coordinated CuI starting materials that were used to prepare novel copper,cyclosulfur adducts, including the first M+,S12 complex (see figure, RF= C(CF3)3, C(CH3)(CF3)2, or CH(CF3)2). Reactions with the [Al{OC(CF3)3}4], counterion mimic gas-phase chemistry inside a mass spectrometer (to form [Cu(S12)]+). An effective route to stable, almost-"naked" CuI salts of weakly coordinating anions (WCAs) of the type [Al(ORF)4], has been developed. Born,Fajans,Haber cycles and theoretical calculations suggest that this methodology is useful for the generation of CuI salts regardless of the larger WCA used. The first homoleptic CuI,arene complex [Cu(1,2-F2C6H4)2]+[Al{OC(CF3)3}4], (1), the first CuI,methylenechloride complex [Cu(CH2Cl2)Al{OC(CH3)(CF3)2}4] (2), and the donor-free dimer [CuAl{OCH(CF3)2}4]2 (3) were synthesized in quantitative yields by sonicating Li[Al(ORF)4] (RF=C(CF3)3, C(CH3)(CF3)2, or CH(CF3)2), AgF, and a three-fold excess of CuI in 1,2-F2C6H4 (1) or CH2Cl2 (2, 3). Substances 1,3 are good starting materials for further CuI chemistry, and the reaction of 1,3 with the weak Lewis base cyclooctasulfur gave the first CuI,sulfur complexes of type [Cu(S12)(S8)]+[Al{OC(CF3)3}4], (4), [Cu(CH2Cl2)(S12)]+[Al{OC(CF3)3}4], (5), [A1Cu(1,5-,1,,1 -S8)CuA1] (6; A1=[Al{OC(CH3)(CF3)2}4],), and a CuI,S8 1D coordination polymer with [Cu2(S8)2A22] (7; A2=[Al{OCH(CF3)2}4],), as a monomeric repeat unit. Complexes 4 and 5 are the first example of any metal coordinated to cyclo-S12 and 4 is the first example of a complex having an element in two allotropic modifications as a ligand. [source] | ||||||||||