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排序方式: 共有114条查询结果,搜索用时 0 毫秒
1.
Wlodzimierz Kutner Winfried Storck Karl Doblhofer 《Journal of inclusion phenomena and macrocyclic chemistry》1992,13(3):257-265
The preparation and properties of smooth and stable films of cyclodextrin polymers are described. The commercially available water soluble prepolymers of-, -, and-cyclodextrin of low molecular masses were crosslinked with glutaric dialdehyde. Side-chain unreacted aldehyde groups were reduced with sodium borohydride. For the-cyclodextrin polymer, optimum film performance was found for a 1:10 mass ratio of glutaric dialdehyde to prepolymer, which corresponds to a molar ratio of glutaric dialdehyde to cyclodextrin units of about 1.75: 1. Such films, of thickness 2.4 µm, were prepared on metallic or glassy-carbon substrates for characterization by scanning-electron microscopy, and for studies with the electrochemical quartz-crystal microbalance. 相似文献
2.
Galezowski W 《Inorganic chemistry》2005,44(15):5483-5494
A two-step mechanism of the reaction of CH(3)Co(III)Pc (Pc = dianion of phthalocyanine) with thiophenoxides in DMA has been confirmed, and the visible spectrum of the inactive transient, CH(3)Co(III)Pc(SAr)(-), has been determined. Rapid rates for ligation of CH(3)Co(III)Pc, yielding CH(3)Co(III)Pc(S-C(6)H(4)-X)(-), are virtually independent of X; this step proceeds probably by an I(d) mechanism. Kinetic data for the follow-up methyl-transfer step yield second-order rate constants and stability constants for CH(3)Co(III)Pc(S-C(6)H(4)-X)(-) consistent with those estimated from concentration dependence of the amplitude of the ligand-exchange step. Cyclic voltammetry provides first reduction potential for CH(3)Co(III)Pc(DMA) of -1.42 V vs Fc(+)/Fc, which makes an OSET mechanism unlikely. Homolytic decay of CH(3)Co(III)Pc(SAr)(-) has also been ruled out. All of the kinetic data, including Hammett's rho = -2.3 +/- 0.1, N-donor inhibition, and alkyl group effect, Me > Et, indicate that the reaction is a normal S(N)2 methyl transfer, only very fast. Methyl transfer to aliphatic thiolates is also rapid and follows the same S(N)2 mechanism. Exceptional methyl-transfer reactivity of the phthalocyanine model sharply contrasting with the inertness of methylcobaloxime is explained. 相似文献
3.
Piotr Kirszensztejn Wlodzimierz Zmierczak 《Reaction Kinetics and Catalysis Letters》1994,52(2):467-474
This study is concerned with the effect of various amounts of Sn species in modifying the dispersity of Al2O3–SnO2 supported platinum catalysts by application of hydrogen chemisorption in a pulse chromatographic system, as well as determination of activity in water-gas shift reaction (WGS). 相似文献
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Wen HW Borejsza-Wysocki W DeCory TR Durst RA 《Analytical and bioanalytical chemistry》2005,382(5):1217-1226
A competitive lateral flow assay for detecting the major peanut allergen, Ara h1, has been developed. The detector reagents are Ara h1-tagged liposomes, and the capture reagents are anti-Ara h1 polyclonal antibodies. Two types of rabbit polyclonal antibodies were raised either against the entire Ara h1 molecules (anti-Ara h1 Ab) or against an immunodominant epitope on Ara h1 (anti-peptide Ab). All of them reacted specifically with Ara h1 in Western Blot against crude peanut proteins. Moreover, the anti-Ara h1 Ab was chosen for this assay development because of its highest immunoactivity to Ara h1-tagged liposomes in the lateral flow assay. The calculated limit of detection (LOD) of this assay is 0.45 g mL–1 of Ara h1 with a dynamic range between 0.1 and 10 g mL–1 of Ara h1 in buffer. Additionally, the visually determined detection range is from 1 to 10 g mL–1 of Ara h1 in buffer. Results using this assay can be obtained within 30 min without the need of sophisticated equipment or techniques; therefore, this lateral flow assay has the potential to be a cost-effective, fast, simple, and sensitive method for on-site screening of peanut allergens. 相似文献
6.
Colin Eaborn Anna Kowalewska Wlodzimierz Stanczyk 《Journal of organometallic chemistry》1998,560(1-2)
The finding that compounds of the type (Me3Si)2(PhMe2Si)CSiMePhX react with electrophiles to give very predominantly rearranged products (Me3Si)2(Ph2MeSi)CSiMe2Y, which would be expected to be thermodynamically disfavoured, can be rationalized in terms of a mechanism in which the anchimerically-assisted departure of X− gives the Ph-bridged cation [(Me3Si)2
MePh]+ which is attacked by the nucleophile at the less hindered centre bearing two Me groups rather than that bearing one Me and one Ph group, with the outcome determined by kinetic rather than thermodynamic factors. Both (Me3Si)2(Ph2MeSi)CSiMe2Br and its isomer (Me3Si)2(PhMe2Si)CSiMePhBr react with AgBF4 in CH2Cl2 or Et2O to give >95% of the fluoride (Me3Si)2(Ph2MeSi)CSiMe2F. Reaction of the bromide (Me3Si)2(PhMe2Si)CSiMePhBr with AgO2CCF3 in Et2O, and that of the hydride (Me3Si)2(PhMe2Si)CSiMePhH with ICl in CCl4, likewise give >95% of the rearranged (Me3Si)2(Ph2MeSi)CSiMe2O2CCF3 and (Me3Si)2(Ph2MeSi)CSiMe2Cl, respectively. 相似文献
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7.
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
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Based on an idea of Rosenblatt, the methods of interpolation theory are used to establish moment inequalities and equivalence relations for measures of dependence between two or more families of random variables. A couple of “interpolation” theorems proved here appear to be new. 相似文献
10.
Wlodzimierz Bryc Victor Kaftal 《Proceedings of the American Mathematical Society》2004,132(2):523-534
Bounds for non-commutative versions of two classical strong mixing coefficients for -Gaussian processes are found in terms of the angle between the underlying Hilbert spaces. As a consequence, we construct a -mixing -Gaussian stationary sequence with growth conditions on variances of partial sums. If classical processes with analogous properties were to exist, they would provide a counter-example to the Ibragimov conjecture.