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21.
Aniela Puszko 《Chemistry of Heterocyclic Compounds》1998,34(2):174-182
The UV spectra of 2-bromopicolines, their N-oxides, and 2-bromo-4-nitropicoline N-oxides are presented and the influence of
substituents onλ
max
andε
max
of spectral bands are discussed. The electronic spectra were calculated using the modified INDO method. Transition energies,
intensities, and assignments were compared with UV spectra. The degree of intramolecular CT in 2-bromopicoline N-oxides is
greater than those in 2-bromopicolines and smaller than those in 2-bromo-4-nitropicoline N-oxides. The differences of the
HOMO-LUMO energies indicate that the susceptibilities in the photochemical reaction lie in the order: 2-bromo-4-nitropicoline
N-oxides>2-bromopicoline N-oxides>2-bromopicolines.
Department of Organic Chemistry, University of Economics, PL-53 342 Wroclaw, Poland. Published in Khimiya Geterotsiklicheskikh
Soedinenii, No. 2, pp. 197–207, February, 1998. 相似文献
22.
Florica Manea Ciprian Radovan Ioana Corb Aniela Pop Georgeta Burtica Plamen Malchev Stephen Picken Joop Schoonman 《Electroanalysis》2008,20(15):1719-1722
An expanded graphite‐epoxy composite electrode (EG‐Epoxy) was employed for the simultaneous determination of 4‐chlorophenol (4‐CP) and oxalic acid (OA) by using cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV). The results indicated that OA could be determined in the presence of the same concentrations of 4‐CP within the concentration range of 0.1 mM to 0.5 mM with a relative standard deviation (RSD) smaller than 5%. Electrode fouling occurred during CA for 4‐CP concentrations larger than 0.5 mM. The DPV method was used for the simultaneous determination of 4‐CP and OA before and after electrochemical oxidation by chronopotentiometry under galvanostatic conditions (j=0.04 mA cm?2, t=2 h) of a tap water sample spiked with 0.19 mM 4‐CP and 0.1 M Na2SO4. 相似文献
23.
Zbigniew Staszak Anna Krojcer Maria Kubiak Aniela Puszko Gabriela Maciejewska Maria Cieślak-Golonka 《Structural chemistry》2010,21(2):305-313
This article presents the electronic spectral characteristics enhanced with the structural, IR and magnetic data of the copper(II) acetate complex with 3-methyl-4-nitropyridine-N-oxide. The complex of the formula, [Cu2(OAc)4(3-mnpn)2], belongs to the group of the ‘paddle wheel’ type species with a very short (2.58 Å) metal–metal distance. In the electronic spectra, new bands were found at 16,000 and 24,000 cm?1, which have been tentatively assigned to the metal–metal interactions and solid state effects, respectively. The complex show fast kinetic exchange of the apical ligand, i.e. 3-methyl-4-nitropyridine-N-oxide. 相似文献
24.
Teobald Kupka Marzena Nieradka Jakub Kaminský Leszek Stobiński 《Magnetic resonance in chemistry : MRC》2013,51(10):676-681
The potential of nuclear magnetic resonance (NMR) technique in probing the structure of porous systems including carbon nanostructures filled with inert gases is analysed theoretically using accurate calculations of neon (21Ne) nuclear magnetic shieldings. The CBS estimates of 21Ne NMR parameters were performed for single atom, its dimer and neon interacting with acetylene, ethylene and 1,3‐cyclopentadiene. Several levels of theory including restricted Hartree‐Fock (RHF), Møller‐Plesset perturbation theory to the second order (MP2), density functional theory (DFT) with van Voorhis and Scuseria's t‐dependent gradient‐corrected correlation functional (VSXC), coupled cluster with single and doubles excitations (CCSD), with single, doubles and triples included in a perturbative way (CCSD(T)) and single, doubles and tripes excitations (CCSDT) combined with polarization‐consistent aug‐pcS‐n series of basis sets were employed. The impact of neon confinement inside selected fullerene cages used as an NMR probe was studied at the RHF/pcS‐2 level of theory. A sensitivity of neon probe to the proximity of multiple CC bonds in C2H2, C2H4, C5H6 and inside C28, C30, C32, C34 and C60 fullerenes was predicted from 21Ne NMR parameters' changes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
25.
A non-enzymatic direct electrochemical glycerol detection method at a commercial boron-doped diamond (BDD) electrode in 0.1 M NaOH supporting electrolyte was developed. All the used electrochemical techniques proved useful features for the oxidation and direct amperometric determination of glycerol at a BDD electrode in 0.1 M NaOH aqueous solution. It was found that the direct electrooxidation of glycerol on the BDD electrode requires both adsorbed glycerol and hydroxyls at the electrode surface. Also, the sp(2) carbon did not allow enhancement of the glycerol oxidation process. The electronalytical sensitivity for the determination of glycerol at the BDD electrode ranged from 0.040 to 0.226 μA mM(-1) as a function of the technique used. The highest electroanalytical sensitivity for the determination of glycerol at the BDD electrode was reached in batch system amperometric quantification under stirring conditions. Performed recovery studies indicated that it is possible to determine glycerol in real samples, and the proposed batch system analysis-based methodology can be a valuable tool for practical glycerol analysis. 相似文献
26.
Vizitiu AE Diudea MV Nikolić S Janezic D 《Journal of chemical information and modeling》2006,46(6):2574-2578
Operations on maps are well-known theoretical tools for transforming a given polyhedral tessellation. Several theoretical investigations of fullerenes, such as their pi-electronic structure and stability, need information on the original map which was transformed into a larger molecular structure. In this respect, retro-operations, particularly those of the most used leapfrog, chamfering, and capra operations, appear particularly useful in searching the associate graphs of fullerenes. A series of analyzed cages proved to be leapfrog transforms of smaller cages. This information was useful in understanding their closed pi-electronic structure and related properties including the local aromaticity. An index based on the optimized geometries enabled the evaluation of aromaticity of their various substructures. Pictorial images of the pi-electron distribution as the main Kekulé valence structures have been performed by the aid of the JSCHEM software package. 相似文献