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1.
A rapid, sensitive, and convenient spectrophotometric assay was developed for the measurement of amino groups on solid supports.
This method is based on the reaction of amino groups of solids with an excess ofo-phthaldialdehyde (OPA) and subsequent quantitative determination of unreacted OPA by reaction with glycine. Four solids possessing
variable quantities of amino groups were examined. Results indicate that about 70% of the total surface amino concentration
(determined by the microKjeldahl method) are available for ligand attachment. Unlike the spectrophotometric 2,4,6-trinitrobenzenesulfonic
acid method, the OPA spectrophotometric assay is more rapid, sensitive, and convenient, and unlike the spectrofluorimetric
OPA, it does not require sophisticated instrumentation. 相似文献
2.
Nicolás D. Gómez Violeta D'Accurso V. Mariana Freytes Francisco A. Manzano Jorge Codnia M. Laura Azcárate 《国际化学动力学杂志》2013,45(5):306-313
An experimental setup that coupled IR multiple‐photon dissociation (IRMPD) and laser‐induced fluorescence (LIF) techniques was implemented to study the kinetics of the recombination reaction of dichlorocarbene radicals, CCl2, in an Ar bath. The CCl2 radicals were generated by IRMPD of CDCl3. The time dependence of the CCl2 radicals’ concentration in the presence of Ar was determined by LIF. The experimental conditions achieved allowed us to associate the decrease in the concentration of radicals to the self‐recombination reaction to form C2Cl4. The rate constant for this reaction was determined in both the falloff and the high‐pressure regimes at room temperature. The values obtained were k0 = (2.23 ± 0.89) × 10?29 cm6 molecules?2 s?1 and k∞ = (6.73 ± 0.23) × 10?13 cm3 molecules?1 s?1, respectively. 相似文献
3.
Violeta Marković Svetlana Marković Ana Janićijević Marko V. Rodić Vukadin M. Leovac Nina Todorović Snežana Trifunović Milan D. Joksović 《Structural chemistry》2013,24(6):2127-2136
A study on the synthesis and mechanistical aspects of formation of 3-methyl-5-oxo-3-pyrazolin-1-carboxamide (MOPC) starting from S-methylisothiosemicarbazide hydrogen iodide and methyl acetoacetate was performed. In the alkaline aqueous solution, the intermediate methyl acetoacetate S-methylisothiosemicarbazone undergoes substitution of CH3S? anion by hydroxide anion, cyclization, carbanion formation, and elimination of methanol, thus yielding corresponding Na-enolate salt of pyrazol-5-one derivative. The structure of the compound obtained after protonation of the formed enolate salt was determined by means of spectroscopic techniques and single-crystal X-ray diffraction analysis. The mechanism of conversion of methyl acetoacetate S-methylisothiosemicarbazone into MOPC was investigated by means of the B3LYP functional, and it was found that the reaction is thermodynamically controlled. 相似文献
4.
11,11′-Dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane], a conventional initiator for grafting polymers from gold surfaces, was synthesized in two steps from 11-mercapto-1-undecanol in 88–92% overall yield. Oxidative dimerization of 11-mercapto-1-undecanol with a catalytic amount of sodium iodide and 30% hydrogen peroxide in ethyl acetate proceeded in 96% yield. Esterification with 2-bromoisobutyryl bromide in dichloromethane was clean and almost quantitative (92% yield) with pyridine used as base, whereas triethylamine gave a messy reaction (64% yield). Alternatively, esterification with 2-bromo-2-methyl-propanoic acid in dichloromethane occurred readily under Steglich's conditions with N,N′-dicyclohexylcarbodiimide (DCC) and a catalytic amount of dimethylaminopyridine (DMAP; 88% yield). 相似文献
5.
Violeta D. Kassabova-Zhetcheva Lilyana P. Pavlova Bisserka I. Samuneva Zara P. Cherkezova-Zheleva Ivan G. Mitov Mikhail T. Mikhov 《Central European Journal of Chemistry》2007,5(1):107-117
Structural and magnetic properties of Mg
x
Zn1−x
Fe2O4 powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg
x
Zn1−x
Fe2O4 (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns
of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes
from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely
small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to
explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts
remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.
相似文献
6.
Parallel Newton two-stage iterative methods to solve nonlinear systems are studied. These algorithms are based on both the multisplitting technique and the two-stage iterative methods. Convergence properties of these methods are studied when the Jacobian matrix is either monotone or an H-matrix. Furthermore, in order to illustrate the performance of the algorithms studied, computational results about these methods on a distributed memory multiprocessor are discussed.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
7.
Violeta Leoreanu 《Southeast Asian Bulletin of Mathematics》2002,25(3):421-426
In this paper, it is proved that the direct limit (inverse limit) of an SHR direct (respectively, inverse) family of SHR semigroups is an SHR semigroup.AMS Subject Classifications Primary 20N20 Secondary 20M99 相似文献
8.
Clifford MN Lopez V Poquet L Williamson G Kuhnert N 《Rapid communications in mass spectrometry : RCM》2007,21(13):2014-2018
We report a systematic investigation of the effects and structural requirements for ion suppression in negative ion mode electrospray ionisation mass spectrometry of a series of carboxylic acids and present a structural model rationalising ion suppression effects. 相似文献
9.
Oliver Moers Violeta Latorre Karl‐Heinz Nagel Armand Blaschette Peter G. Jones 《无机化学与普通化学杂志》2003,629(1):83-90
Polysulfonylamines. CLX. Crystal Structures of Metal Di(methanesulfonyl)amides. 10. The Three‐Dimensional Coordination Polymers M[(CH3SO2)2N], where M is Potassium, Rubidium, Cesium (Isotypic Structures for M = K, Rb) Low‐temperature X‐ray crystal structures are reported for KA (monoclinic, space group P21/c, Z′ = 1), RbA (isotypic and isostructural with KA), and CsA (monoclinic, P21/n, Z′ = 1), where A— denotes the anion obtained by deprotonation of the strong nitrogen acid (MeSO2)2NH. In KA and RbA, the anion is distorted into a rare C1 conformation, whereas the standard C2 conformation is retained in the cesium complex. The structures consist of three‐dimensional coordination networks, in which each cation adopts an irregular (O6N)‐heptacoordination by forming close contacts to one (O, N)‐chelating, one (O, O)‐chelating and three κ1O‐bonding ligands; however, the coordination number for Cs+ is effectively increased to 8 by a very short Cs···Cs contact distance of 422.5 pm. The crystal packings of the isotypic compounds KA and RbA display lamellar layer substructures that involve six independent ligand‐metal bonds and comprise an internal cation lamella and peripheral regions built up from anion monolayers; the 3D framework is completed by one independent M—O bond cross‐linking the layer substructures. In contrast, CsA features anion monolayers that intercalate planar zigzag chains of cations (Cs···Cs alternatingly 422.5 and 487.5 pm, Cs···Cs···Cs 135.7°), whereby each chain is surrounded and coordinated by four anion stacks and each anion stack connects two cation chains. All structures exhibit close C—H···A interanion contacts consistent with weak hydrogen bonding. 相似文献
10.
Dejan Poleti Ljiljana Karanovi Vukadin M. Leovac Violeta S. Jevtovi 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):m73-m75
The title compound, dibromo(3‐hydroxy‐5‐hydroxymethyl‐2‐methyl‐4‐pyridinecarboxaldehyde semicarbazone‐κ3N1,O3,O3′)copper(II), [CuBr2(C9H12N4O3)], consists of discrete complex units with the tridentate pyridoxal semicarbazone ligand as a zwitterion in an almost planar configuration. The CuII ions are in a distorted square‐pyramidal coordination, with the equatorial Br atom at a distance of 2.4017 (6) Å and the apical Br atom at a distance of 2.6860 (6) Å. 相似文献