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61.
Rate constants for the reaction of ethyl bromoacetate with three series of substituted naphthoate ions have been measured
in an acetone-water mixture (90% v/v). Using σ
p
values rate constants at 30o correlate well with the Hammett equation yielding ρ=−0.54, −0.19 and −0.25 for (4,1−), (6,1−) and (6,2−) series, respectively.
Comparison of these ρ values with those of the reaction of phenacyl bromide reveals the failure of the reactivity-selectivity
principle RSP in these reactions. Failure of RSP has been explained in terms of isoselective temperature. 相似文献
62.
Parac-Vogt TN Pacco A Nockemann P Laurent S Muller RN Wickleder M Meyer G Vander Elst L Binnemans K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,12(1):204-210
Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded between 0.24 mT and 1.4 T for lanthanum(III)- and gadolinium(III)-containing [15]metallacrown-5 complexes derived from alpha-aminohydroxamic acids and with copper(II) as the ring metal. The influence of the different R-groups on the proton relaxivity was investigated, and a linear relationship between the relaxivity and the molecular mass of the metallacrown complex was found. The selectivity of the metallacrown complexes was tested by transmetalation experiments with zinc(II) ions. The crystal structure of the copper [15]metallacrown-5 gadolinium complex with glycine hydroximate ligands is reported. 相似文献
63.
B. F. Myasoedov L. A. Gribov A. I. Pavlyuchko I. V. Rybalchenko G. I. Sigeikin A. F. Kireev V. N. Suvorkin 《Journal of Structural Chemistry》2006,47(3):434-441
For highly toxic organophosphorus compounds on the limiting lists of the International Chemical Weapons Ban Treaty, fragment methods may be used for calculating their IR vibrational spectra; this is shown for O-alkyl alkylfluorophosphonates used as examples. The geometrical parameters and the parameters of the potential and electrooptic functions are found for the major fragments of these compounds. Due to this, fast predictive computation of IR spectra of O-alkyl alkylfluorophosphonates is possible, the accuracy of calculation being sufficient for spectral identification of these compounds; a database of the calculated IR spectra may be created. 相似文献
64.
Electrophoretic mobilities of hexadecane/water emulsions containing dimyristoyl-phosphatidylcholine (DMPC) or egg yolk lecithin
(EYL) monolayers at the interface and those of liposomes prepared from the same lipids were measured as functions of the concentrations
of Ca2+, Mn2+, Cu2+, and Ni2+ cations in the aqueous phase. The surface potentials, surface charge densities (σ), and the Langmuir adsorption isotherms
for various distances from the charged surface to the slip plane (d) were calculated on the basis of the Gouy-Chapman theory for 1∶2 electrolytes and the values of ζ-potentials. The binding
constants (K) and parametersd were determined under the assumption that the maximum σ values correspond to one ion per phospholipid molecule at the interface.
In the case of DMPC, the ion binding constants (L mol−1) at 25°C are 230 and 87 for Ca2+, 31.5 and 21 for Mn2+, 11 and 6 for Cu2+, and 7.5 and 5.3 for Ni2+ in liposomes and emulsions, respectively. The affinities of Cu2+ and Ni2+ ions for EYL monolayers and bilayers are lower than those for DMPC mono- and bilayers. Thed parameters for all ions are smaller than the radii of the hydrated ions. In the case of Ca2+, Cu2+, and Ni2+, thed values for mono- and bilayers are different. The differences in K values between monolayers and bilayers as well as those
between DMPC and EYL mono- and bilayers can be attributed to the differences in the local environment and orientation of the
interfacial phosphate groups in these systems.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2490–2495, December, 1998. 相似文献
65.
S. Bhattacharyya A. N. Sil T. K. Mukherjee P. K. Mukherjee P. Vasu 《International journal of quantum chemistry》2007,107(4):946-951
Electron affinity of plasma embedded muonium (μ+e?) and pionium (π+e?) has been estimated using a general three‐body formalism within variational framework. Electron correlation is taken care of using extended Hylleraas basis sets. The stability of the three‐body systems have been studied under the Debye screening model of the plasma, which changes the Coulombic potential to the screened Coulomb one. The electron affinity of the muonium and pionium is maximum for free systems, and it decreases gradually toward zero with increase of the plasma strength, which tends to push the three‐body system toward gradual instability. The electron correlation contribution to the affinity has been analyzed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
66.
M. Eddaoudi A. W. Coleman P. C. Junk 《Journal of inclusion phenomena and macrocyclic chemistry》1996,26(1-3):133-151
The solubilities of -, -, and -cyclodextrin have been measured in the presence of the first row transition metals: Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+; chlorides, nitrates and sulphates (in this case Fe2+), and, for companson, with CaCl2, the corresponding Group IIa salt. Where possible the measurements are reported as a function of the activity of the salts. In general, for the transition metals the sulphates all show a linear decrease in solubility with increasing salt activity: for the nitrates the solubility increases and then reaches a limiting value; and for the chlorides a small decrease in solubility is observed at low activity followed by an increase in solubility at higher salt activity. Circular dichroism measurements confirm that there is no direct complexation at non-basic pH.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August 1995. 相似文献
67.
Removal of Endotoxin from Human Serum Albumin Solutions by Hydrophobic and Cationic Charged Membrane 总被引:1,自引:0,他引:1
Removal of end6toxin from medicine injection is very important, becauseendotoxin withpotential biological activity causes pyrogenic and shock reactions in' mammals-'on...intravenous injection even as law as "an6gram amounts. Endotoxin, a constituent ofpotential contaminant of physiological fluids and aqueous solutions 'and very stable atextreme temperature and PH values. For removing endotoxin from solutions ofbiomolecules, such as HSA, adsorption techniques are usedl.' Many methods forendot… 相似文献
68.
The photophysics and photochemistry of alpha-terthiophene (alphaT), compartmentalized in mixed nonionic/anionic micelles, have been investigated with focus on the influence of the micellar surface charge density on the formation of the radical coupling product alpha-hexathiophene (alphaH). By varying the ratio of nonionic-to-anionic surfactants, and assuming ideal mixing, the charge density of the mixed micelles was varied. From Poisson-Boltzmann calculations, performed using the cell model, the electrostatic potential and the counterion activity were estimated as a function of the distance from the micellar surface. Upon excitation, the triplet state of alphaT is formed, from which the alphaT radical cation can be formed by absorption of a second photon. The radical cation can form alphaH if it encounters another alphaT radical cation. Under the experimental conditions used, this implies that the alphaH formation only occurs if the compartmentalized radical cation is able to migrate from its host micelle to another micelle, either via the surrounding bulk or by fusion of two micelles followed by mixing of their contents before micellar fission. The formation yield of the radical cation depends on the charge density of the mixed micelle; a lower charge density, that is, an increased amount of nonionic surfactant, lowers the yield. The yield of the coupling product alphaH, however, does not follow the same trend. A maximum yield of alphaH is found at intermediate nonionic surfactant molar ratios. This behavior is understood in terms of the Poisson-Boltzmann simulation results and by comparing charge-density changes as a function of molar fraction with the changes in counterion activity. The alphaH yield is a result of the balance between an increased possibility of radical cation bulk migration and a lowered electrostatic stabilization of the radical. 相似文献
69.
Fluorescence signalling of the transition metal ions: Design strategy based on the choice of the fluorophore component 总被引:1,自引:0,他引:1
Transition metal ions are notorious for their fluorescence quenching abilities. In this paper, we discuss the design strategies
for the development of efficientoff-on fluorescence signalling systems for the transition metal ions. It is shown that even simplefluorophore-spacer-receptor systems can display excellentoff-on fluorescence signalling towards the quenching metal ions when the fluorophore component is chosen judiciously. 相似文献
70.
Circular high-performance thin-layer chromatography (HPTLC) has been used to differentiate a series of twelve tricyclic neuroleptics, using both normal phase and reverse phase procedures. The use of normal phase systems also allows the resolution of geometric isomers of chlorprothixene, clopenthixol and flupenthixol. Thirteen sulphonamides and Trirnethoprim may also be distinguished using HPTLC. 相似文献