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1.
Virender K. Sharma Fabien Casteran Frank J. Millero Concetta De Stefano 《Journal of solution chemistry》2002,31(10):783-792
The sulfur-containing biomolecule, cysteine has a role in physiological and natural environment because of its strong interactions with metals. To understand these interactions of metals with cysteine, one needs reliable dissociation constants for the protonated cysteine species [
CH(CH2SH)COOH; H3B+]. The values of dissociated constants, p
, for protonated cysteine species (H3B+ H+ + H2B, K
1; H2B H+ + HB–,K
2; HB– H+ + B2–,K
3) were determined from potentiometric measurements in NaCl solutions as a function of ionic strength, 0.5–6.0 mol-(kgH2O)–1 and between 5, and 45°C. The equations
were fitted to the results with a standard errors of the fits of 0.116, 0.057, and 0.093 for
,
, and
, respectively. The
results were used to determine new Pitzer parameters (0, 1, and C) for the interactions of Na+ and Cl– with cysteine species. These coefficients can be used to make reasonable estimates of the activity coefficients of the cysteine species and
for the dissociation of cysteine in physiological and natural waters containing mostly NaCl. 相似文献
2.
Werner Mikenda 《Monatshefte für Chemie / Chemical Monthly》1986,117(8-9):977-984
IR spectra of 3 normal solutions of 14 different salts [chlorides of Al+++, Be++, Mg++, Ca++, Sr++, Ba++, Zn++, Cd++, Li+, Na+, K+, Rb+, Cs+, N(CH3)
4
+
] in both, 96% H2O+4% D2O and 100% H2O, were measured in the frequency range
=2 800–2 100 cm–1. From up to 18 single measurements for each solution the frequencies and halfwidths of the O-D stretching bands of isotopically dilute HDO were determined with high accuracy. Frequencies in the range
=2 510–2 529 cm–1 and halfwidths in the range
=155–205 cm–1 resulted atT=30°C with standard deviations typical less than ±1 cm–1 and ±4 cm–1, respectively. An almost perfect correlation between the O-D stretching band parameters and the polarizing power of the cations was obtained.Herrn Prof. Dr.A. Neckel, Wien, zum 60. Geburtstag gewidmet. 相似文献
3.
4.
Summary The oxidation of H2O2 by [W(CN)8]3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law,
, strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k
s, given by
, involves the formation of [W(CN)8· H2O2]3–, [W(CN)8· H2O2·W(CN)8]6– and [W(CN)8· HO]3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)8·HO]3– (k
a) and its conjugate base [W(CN)8·O]4– (k
b). At 25 °C, I = 0.20 m (NaCl), the rate constant
with H
a
=40±6kJmol–1 and S
a
=–151±22JK–1mol–1; the rate constant
with H
b
=36±1kJmol–1 and S
b
=–136±2JK–1mol–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)8·HO]3–, K
5
=(5.9±1.7)×10–10
m, with
and
is the first acid dissociation constant of H2O2. The second pathway, with rate constant, k
f, involves the formation of [W(CN)8· HO2]4– and is followed by a formal two-electron redox process with [W(CN)8]3–. The pH-dependent rate constant, k
f, is given by
. The rate constant k
7
=23±6m
–1
s
–1 with
and
at 25°C, I = 0.20 m (NaCl). 相似文献
5.
V. V. Burdin G. I. Voloshchenko V. D. Maiorov N. B. Librovich 《Russian Chemical Bulletin》1995,44(9):1684-1687
Multiple Attenuated Total Reflectance (MATR) IR spectra of solutions of HCl in isopropanol, containing 0 to 43 mol. % HCl, were studied in the 900–4000 cm–1 range. The addition of HCl to PriOH yields proton disolvates
with strong symmetrical H-bonds. At high concentrations of HCl (C
HCl
0 > 5.7 mol L–1,
/C0
HCl < 2), when the number of alcohol molecules is not enough to form disolvates with all of the protons present in the solution, (Cl...H...Cl)– ions are formed, in addition to (C3H7OH)2H+. The spectra of these ions have been assigned.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1753–1756, September, 1995.This work was carried out with financial support of the Russian Foundation for Basic Research (Project No. 93-03-18356). 相似文献
6.
O. A. Gherco 《Russian Journal of Coordination Chemistry》2005,31(8):597-602
A new Cu(II) complex [Cu(HPht)2(1-CH3Im)2] (I), where HPht is the monoanion of o-phthalic acid and 1-CH3Im is 1-methylimidazole, is synthesized and characterized by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis. Compound I contains molecular complexes in which the o-phthalic acid residue is monodeprotonated and linked to a metal through the carboxyl group in a 1,3-chelate mode. The cis-octahedral coordination of copper is formed by two HPht residues and two 1-CH3Im molecules. The distances are Cu-N1.945(6) Å, Cu-O2.018(5) Å and 2.374(6) Å. Polymeric chains are formed in complex I due to intermolecular
hydrogen bonds. The chains are unified into layers by the
interactions between the 1-CH3Im molecules of the adjacent complexes.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 630–635.Original Russian Text Copyright © 2005 by Gherco. 相似文献
7.
The solubility of Cd(OH)2(c) was studied in 0.01M NaClO4 solutions, from both the over- and the undersaturation directions, with OH– ion concentration ranging from 10–6 to 1.0 mol-L–1, and the equilibration period ranging from 2 to 28 days. Equilibrium Cd concentrations were reached in less than 2 days. The Cd(OH)2(c) solubility showed an amphoteric behavior. In the entire range of OH–/H+ investigated, the only dominant aqueous Cd(II) species required to explain the solubility of Cd(OH)2(c) are Cd2+, Cd(OH)
2
0
, and Cd(OH)
4
2–
. The logarithms of the thermodynamic equilibrium constants of the Cd(OH)2(c) solubility reactions involving these species, that is, the reactions
相似文献
8.
A structural study of saturated aqueous solutions of some alkali halides by X-ray diffraction 总被引:2,自引:0,他引:2
The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H2O)–1], KCI [4.56 mol (kg H2O)–1], KF [16.15 mol (kg H2O)–1] and CsF [31.96 mol (kg H2O)–1] has been investigated by means of solution X-ray diffraction at 25°C. In the NaCI and KCI solutions about 30% and 60%, respectively, of the ions form ion pairs and the Na+–Cl– and K+–Cl– distances have been determined to be 282 and 315 pm, respectively. The average hydration numbers of Na+ and Cl– ions are 4.6 and 5.3, respectively, in the NaCI solution and those of K+ and Cl– ions in the KCI solution are both 5.8. In the KF solution, clusters containing some cations and anions, besides 1:1 (K+–F–) ion pairs, are formed. The K+–F– interatomic distance has been determined to be 269 pm, and nonbonding K+...K+ and F–...F– distances in the clusters are 388 and 432 pm, respectively, and the average coordination numbers n
KF
, n
KK
and n
FF
have been estimated to be 2.3, 1.9, and 1.6, respectively. In the highly supersaturated CsF solution an appreciable amount of clusters containing several caesium and fluoride ions are formed. The Cs+–F– distance in the cluster has been determined to be 312 pm, while the nonbonding Cs+...Cs+ and F–...F– distances are estimated to be 442 and 548 pm, respectively, the distances being about
and
times the Cs+–F– distance, respectively. The coordination numbers n
CsF
, n
CsCs
, and n
FF
in the first coordination sphere of each ion are 3.3, 2.3 and 5.3, respectively, and the result shows the formation of clusters of higher order than 1:1 and 2:2 ion pairs. These ion pairs and clusters may be regarded as embryos for the formation of nuclei of crystals and the results obtained in the present diffraction study support observations for the nucleation of the alkali halide crystals studied by molecular dynamics simulations previously examined. 相似文献
9.
Yue Tingsheng Qui Ling Ma Yongli Liang Jianjun 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(4):321-329
The ion exchange processes of
(OAc–) and
(OAc–) proceeding in shell-core inorganic ion exchanger Ti (HPO4)2·1/2H2O has been studied and the diffusion equation whose boundary conditions are satisfied by a shell-core model was solved. Based on the equation solved and experimental data, the diffusion coefficients corresponding to the exchange process
(OAc–) and Li+–H+ (OAc–) at 17°C are found to be 7.7×10–9 and 6.2×10–8 cm2 s–1 and the activation energies 3.4×104 and 5.0×103 J mol–1, respectively. Compared to the gel type of styrene-divinylbenzene strong acid exchanger with 20% cross linking, it can be concluded that the rate of
or
exchange is 3.5 times faster than that in the organic exchanger.TIP was obtained from the Salt Lake Institute of the Academy of Science of China. 相似文献
10.
Solid-solute phase equilibria in aqueous solutions,VIII: The standard gibbs energy of La2(CO3)3·8H2O
Anh Mai Nguyen Erich Königsberger Harald Marhold Heinz Gamsjäger 《Monatshefte für Chemie / Chemical Monthly》1993,124(10):1011-1018
The solubilities of lanthanum carbonate La2(CO3)3·8H2O in solutionsS
0([H+]=H mol kg–1, [Na+]=(I–H) mol kg–1, [ClO
4
–
]=I mol kg–1) at various fixed partial pressures of CO2 have been investigated at 25.0 °C. The hydrogen ion molality and the total molality of La(III) ion in equilibrium with the solid phase were determined by e.m.f. and analytical methods, respectively. The stoichiometric solubility constants
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