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111.
Adam S. Plaziak Jaroslaw Spychala Hanna Wjtowicz Jerzy J. Langer Halina Thiel-Pawlicka Krzysztof Golankiewicz 《Journal of mass spectrometry : JMS》1992,27(11):1293-1298
Ortho-. meta- and para-isomers of N-(pyrimidin-4-yl)aminobenzoic acid and their methyl esters were investigated by electron impact mass Spectrometry. Their fragmentation was found to be strongly dependent on the position of the substituent in the aminobenzoic moiety. Two different kinds of ortho effect were studied and confirmed with the aid of deuterium-labelled derivatives. 相似文献
112.
W. K. Jóźwiak T. P. Maniecki A. Basińska J. Góralski R. Fiedorow 《Kinetics and Catalysis》2004,45(6):879-889
This paper is focused upon the influence of potassium on the reduction behavior and catalytic properties of Fe2O3, Ru/Fe2O3 and Ru/(K)Fe2O3 catalysts for the water gas shift (WGS) reaction. The effect of promotion by potassium is attributed to stabilization of a highly dispersed ruthenium phase on the iron oxide surface. The hydrogen reduction behavior of Fe2O3 catalysts is strongly influenced by time-pressure dependent processes and comprises two or three heavily overlapped TPR peaks which can be ascribed to the following stages of the iron(III) oxide reduction 3Fe2O3 2Fe3O4 6FeO 6Fe. The appearance of FeO as an intermediate phase was confirmed by XRD. The presence of ruthenium(IV) oxide substantially changes the kinetics of the reduction process. In the case of potassium-doped catalysts, the reduction of Fe2O3 is substantially different and is assigned to the reduction phase of KFeO2. Both ruthenium and potassium have a promoting effect on the catalytic activity for the WGS reaction.From Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 930–941.Original English Text Copyright © 2004 by Jówiak, Maniecki, Basiska, Góralski, Fiedorow.This article was submitted by the authors in English. 相似文献
113.
Low molecular weight tri-podal biphenyl- and benzoate-type mesogens [C6H5C6H4O(CH2)5SiMe2CH2CH2SiMe2]3CH (4), [C11H23O(C6H4)2O(CH2)5SiMe2]3CH (5) and [MeOC6H4OC(O)C6H4O(CH2)5SiMe2]3CH (6) (C6H4 = 1,4-phenylene) were obtained, from branched silyl substituted methane precursors [CH2CH(Me)2Si]3CH (1) and (HMe2Si)3CH (2). The biphenyl-containing ones (4) and (5) were converted into terminal alkenes, which were subsequently hydrosilylated with poly(methylsiloxanes). The polymer derived from (5) exhibited mesomorphic properties. Such systems have the potential to significantly increase the density of liquid crystal rod-like structures in side chains of linear polymers (or dendritic liquid crystal polymers). 相似文献
114.
Tritium exchange at C-8 of xanthosine, theobromine, 1-, 3- and 7-methylxanthine in water has been studied. The rates of detritiation of these compounds have been determined over a pH range at constant temperature. Several mechanisms of exchange involving various ionic forms of substrate operating at different pH have been suggested. 相似文献
115.
The refined theory of the electroviscous lift forces is presented for the case when the separation distance between the particle and the wall is larger than the double-layer thickness. The theory is based on the lubrication approximation for motion of a long cylinder near a solid wall in creeping flow. The approximate analytical formula for the lift force valid for Pe=1 is derived and compared with the results of numerical calculations performed for an arbitrary Peclet number. The resulting electrokinetic lift force exceeds by several orders of magnitude one predicted by the previously developed theories of the lift force. The results for the electroviscous drag force indicate that when the double layer is thin compared with the particle size, the electroviscous drag is only a small correction (at most 10%) to the hydrodynamic drag force acting on a neutral particle moving near the wall. Copyright 2000 Academic Press. 相似文献
116.
Magdalena Biesaga Elzbieta Stolarczyk Krystyna Pyrzyńska Marek Trojanowicz 《Analytical sciences》2002,18(2):151-154
The silica-based Fe(III)-protoporphyrin and Zn-tetraphenylporphyrin stationary phases were examined for the HPLC separation of anions. The retention of nine common inorganic anions as well as benzoate anion (BA) and its hydroxy analogues (HBA) was examined using tartrate, acetate, and succinate eluents. The retention factors of inorganic anions on the FeProP stationary phase were in the order Cl- < NO3- < ClO4- < I- < SCN- and for organic anions benzoate < p-hydroxybenzoate < m-hydoxybenzoate < o-hydroxybenzoate. The retention factors of organic anions examined for a ZnTPP column were in the order p-HBA < m-HBA < BA < o-HBA. 相似文献
117.
J. Magoński 《Journal of solution chemistry》1990,19(6):597-607
The significant role of the proton exchange and homoconjugation (formation of AHA– and A1HA
1
–
complexes) equilibria in protonic hetero systems (HA+A
1
–
) has been shown from analysis of published data and from my own simple experiments. It is concluded that there is a need to reconsider some basic hydrogen bond problems. One of these problems-the existence of heteroconjugates in polar solvents — has been verified and illustrated with suitable experimental evidence (IR and UV-VIS spectra). The most accepted experimental evidence for the double minimum potential in the hydrogen bridge has been questioned as being in disagreement with the equilibrium law. A simple relation between the heteroconjugation constant, the parent homoconjugation constants and the proton exchange constant is also postulated. This relation fulfills important theoretical requirements, however, it is not applicable in extreme cases.To the memory of Bogdan Przybyszewski. 相似文献
118.
Jolanta Obniska Krzysztof Kaminski Agnieszka Dzierzawska-Majewska 《Journal of fluorine chemistry》2006,127(3):417-425
A series of N-phenyl- and N-benzyl-2-azaspiro[4.4]nonane- and [4.5]decane-1,3-diones containing a fluoro or trifluoromethyl substituents at the aryl ring was synthesized and tested for their anticonvulsant activity in the maximal electroshock (MES) and subcutaneous metrazole (sc.Met) tests. Among them, the most active were N-benzyl derivatives with fluoro and trifluoromethyl substituents especially at position-2 of the aryl moiety. The introduction of the phenyl ring at the imide nitrogen atom resulted in less active compounds. The results obtained showed that incorporation of fluoro or trifluoromethyl substituents increased the anticonvulsant activity in comparison to respective chloro, methoxy or methyl analogues. Crystallographically obtained conformation for one active and two inactive derivatives with trifluoromethyl substituents at position-2 or -3 of phenyl ring were initially used for molecular electrostatic potentials (MEP) calculation. The MEP distribution at carbonyl oxygen atoms was different for active and inactive molecules. 相似文献
119.
Gibasiewicz K Szrajner A Ihalainen JA Germano M Dekker JP van Grondelle R 《The journal of physical chemistry. B》2005,109(44):21180-21186
Almost all photosystem I (PSI) complexes from oxygenic photosynthetic organisms contain chlorophylls that absorb at longer wavelength than that of the primary electron donor P700. We demonstrate here that the low-energy pool of chlorophylls in the PSI-LHCI complex from the green alga Chlamydomonas reinhardtii, containing five to six pigments, is significantly blue-shifted (A(max) at 700 nm at 4 K) compared to that in the PSI core preparations from several species of cyanobacteria and in PSI-LHCI particles from higher plants. This makes them almost isoenergetic with the primary donor. However, they keep the other characteristic features of "red" chlorophylls: clear spectral separation from the bulk chlorophylls, big Stokes shift revealing pronounced electron-phonon coupling, and large homogeneous and inhomogeneous broadening of approximately 170 and approximately 310 cm(-1), respectively. 相似文献
120.
ABSTRACT Novel chiral three-ring (R) enantiomers were synthesised using optically active (R)-(?)-2-octanol. Properties, such as the sequence of phases, the transition temperatures and enthalpies, were tested by a polarising optical microscope and differential scanning calorimeter. An antiferroelectric smectic phase (SmCA*) with a direct transition from the antiferroelectric to the isotropic phase (SmCA*-Iso) was observed for three esters with an achiral C3F7CH2O(CH2)3O– terminal chain. Bi- and multicomponent mixtures with a broad temperature range of the antiferroelectric phase and good electro-optical properties were formulated. Helical pitch of pure esters and mixtures was measured by spectrophotometry method. 相似文献