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41.
Marciniec B Majchrzak M Prukała W Kubicki M Chadyniak D 《The Journal of organic chemistry》2005,70(21):8550-8555
(E)-N-(Silyl)vinylcarbazole has been easily prepared via a new catalytic route, silylative coupling (SC) of vinylcarbazole with vinyltrisubstituted silanes catalyzed by [RuH(Cl)(CO)(PCy3)2]. X-ray structures of two silylvinylcarbazoles as first N-vinylcarbazole derivatives have been resolved. The Pd-catalyzed Hiyama coupling reaction (also as the tandem reaction with SC) of synthesized (E)-N-(triethoxysilyl)vinylcarbazole with iodobenzene has been performed to afford (E)-N-(phenylvinyl)carbazole with high yield and stereoselectivity. 相似文献
42.
Frantiek Hrabk Vlasta Hynkov Milan Bezdk 《Journal of polymer science. Part A, Polymer chemistry》1969,7(4):1111-1113
Some simple equations for the emulsion polymerization system were derived on the basis of the Smith-Ewart theory. These are used in calculating the molar monomer concentration and rate of polymerization in units of moles per liter per second for the zero-order region with respect to the monomer as well as in calculating the rate constant of the growth reaction. 相似文献
43.
Kyselová Z Kysel'ová Z Krizanová L Soltés L Stefek M 《Journal of chromatography. A》2005,1084(1-2):95-100
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of eye lens proteins showed that both progression of diabetic cataract in rats in vivo and precipitation of soluble eye lens proteins stressed by free radicals in vitro were accompanied by significant protein cross-linking. There was a noticeable contribution of disulfide bridges to protein cross-linking in diabetic eye lens in vivo. In contrast, under conditions in vitro, when eye lens proteins were exposed to hydroxyl or peroxyl radicals, we showed that the participation of reducible disulfide linkages in the formation of high molecular mass products was markedly lower. These in vivo--in vitro differences indicate that the generally accepted role of reactive oxygen species in diabetic cataractogenesis may be overestimated in connection with the processes of protein cross-linking. 相似文献
44.
Jozef Rychlý Lyda Matisov-Rychl Milan Lazr Ivica Janigov Matija Strli
Drago Ko
ar Jozef Hanus Jarmila Minrikov Svetozr Katu
k 《Comptes Rendus Chimie》2006,9(11-12):1425
Whatman cellulose impregnated with calcium and magnesium carbonates was oxidized and chemiluminescence accompanying this oxidation has been measured. It was shown that magnesium ions in deacidified cellulose pulp promote the light emission significantly. On the other hand, acid papers give the more pronounced light signals at temperatures close to ambient. The relation between chemiluminescence runs and paper degradation has been implicated, with an attempt to extrapolate half-lives of paper samples to conditions close to ambient. To cite this article: J. Rychlý et al., C. R. Chimie 9 (2006). 相似文献
45.
The first crystallographic data for sigma-bonded alkylcobalt(III) phthalocyanine complexes are reported. A single-crystal X-ray structure of CH(3)CH(2)Co(III)Pc (Pc = dianion of phthalocyanine) reveals that the solid consists of centrosymmetric face-to-face dimers in which the CH(3)CH(2)Co(III)Pc units retain their square pyramidal geometry. The structure appears to be the first one reported for a five-coordinate RCo(III)(chelate) complex with an electron-deficient equatorial system. The Co-C bond in CH(3)CH(2)Co(III)Pc (2.031(5) A) is the longest found in five-coordinate RCo(III)(chel) complexes (R = simple primary alkyl group). Another X-ray study demonstrates that CH(3)Co(III)Pc(py) has a distorted octahedral geometry with axial bonds of very similar length to those in methylcobalamin. The axial bonds are shorter than those in its octaethylporphyrin analogue, in accordance with a weaker trans axial influence in six-coordinate complexes containing an electron-deficient phthalocyanine equatorial ligand. A different trend has been observed for five-coordinate RCo(III)(chel) complexes: electron-rich equatorial systems seem to make the Co-C axial bond shorter. Kinetic data for the homolysis of RCo(III)Pc complexes (R = Me, Et) in dimethylacetamide are also reported. Homolysis of ethyl derivatives is faster. The Co-C bond dissociation energies (BDEs) for the pyridine adducts of the methyl and the ethyl derivative are 30 +/- 1 and 29 +/- 1 kcal/mol, respectively. The BDE for CH(3)CoPc(py) is considerably lower than that for MeCbl despite the very similar lengths of the axial bonds in the two complexes. The results of this work do not support any correlation between the Co-C bond length and the bond strength as defined by BDE. 相似文献
46.
Štefan Marchalín Dušan Ilavský Milan Bruncko 《Monatshefte für Chemie / Chemical Monthly》1989,120(12):1101-1105
Summary Good yields of substituted 5-(5R-2-furyl)-4H-pyrano[2,3-d]pyrimidines4 were obtained in the reaction of 2-ethoxymethyleneamino-3-cyano-4H-pyranes2 with ammonia. Compounds2 were prepared by the condensation of the starting 2-amino-5-acetyl-3-cyano-6-methyl-4H-pyranes1 with ethyl orthoformate. Spectral properties of the bicyclic system4 in relation to compounds3 are discussed. 相似文献
47.
Stationary phase containing quinolin-8-ol immobilized on macroporous methacrylate support for the affinity chromatography of porcine pepsin A is described. Optimized chromatographic conditions for separation of porcine pepsin A on this stationary phase were found investigating the influence of pH, concentration, ionic strength and chemical composition of the used mobile phases. The stationary phase shows a good reproducibility of chromatographic analyses (relative standard deviation, +/-2%), a high recovery (ca. 93%) and a satisfactory capacity (13 mg pepsin A/1 mL stationary phase) for porcine pepsin A. The obtained findings confirm the applicability of affinity chromatography on the stationary phase with immobilized quinolin-8-ol to the isolation and determination of porcine pepsin A. 相似文献
48.
Milan Randić 《Journal of mathematical chemistry》1987,1(1):145-152
The use of power sum symmetric functions leads to Newton's identities, which relate the traces of various powers ofA, the adjacency matrix of a graph, and the coefficients of the characteristic polynomials. While it is possible to solve Newton's identities and generate the coefficients by recursion or, alternatively, to derive them by sequential manipulations (yielding the explicit formulas), we show how the results can be expressed using a combinatorial approach and relate the evaluation of the coefficients to selected Young diagrams. 相似文献
49.
By adopting the convention that shared double bonds in polycyclic conjugated hydrocarbons contribute with one -electron and unshared ones with two -electrons, a partition of -electrons in each ring (-electron content, EC) can be obtained by averaging over all Kekulé structures, which are assumed to have equal weights. This affords a simple measure of local aromaticity that is comparable with other such local aromaticity indices in polycyclic benzenoids. 相似文献
50.
A set of original, analytical equations useful for theoretical calculation of the electron paramagnetic resonance (EPR) signal intensity are presented for the multitude of sample shapes, which range from point-like, line-like, planar, rectangular, cubical, circular, cylindrical, spherical to an irregularly shaped sample. The samples can be situated at any available position within the prescribed part of the microwave cavity (a central cylinder of diameter 11 mm and length 23.5 mm, in either a Bruker single TE102 or double TE104 rectangular cavity, with the modulation coils situated in the left and right side cavity walls, which is connected to a X-band, field-modulated CW Bruker EPR spectrometer). The theoretical computations of EPR signal intensity can be used in the computer simulations in which: (i) the EPR signal intensity profiles are constructed; (ii) the optimal sample positions in the cavity to give a maximum value of signal intensity are found; (iii) the errors associated with sample positioning within the cavity when compared to a second sample of a different size, shape or position are studied. 相似文献