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121.
Ângela F. S. S. Mendonça Dina T. R. Formigo Isabel M. S. Lampreia 《Journal of solution chemistry》2002,31(8):653-670
Solubilities of triethylamine in aqueous tetraethylammonium chloride solutions were measured at 20, 25, and 35°C. The molalities in Et4NCl of the aqueous solvents ranged from 0.03 to 1 mol-kg–1. The data were evaluated from density measurements using a vibrating-tube densimeter. At each temperature, least-squares method was used to fit experimental density data points to double polynomial equations of various degrees. Triethylamine molalities of the saturated aqueous phases were estimated by extrapolation from those equations. Experimental data were interpreted in terms of hydrophobic and electrostatic perturbed domains in the hydration shells of the noneleceory and of the cation of the salt, as a function of temperature and salt concentration. The conclusions obtained are consistent with previous volumetric studies. 相似文献
122.
Partial molar volumes for a homologous series of amino acids and peptides have been measured in aqueous 1M sodium acetate, sodium thiocyanate, and sodium sulfate at 25°C. These data have been utilized in conjunction with the data in water to deduce partial molar volumes of transfer V
2,m
0(tr) from water to these aqueous salt solutions. The volumes of transfer for the amino acids and peptides are found to be positive. The interpretation is that this result arises from the dominant interaction of the sodium salts with the charged centers of amino acids and peptides. Thermal denaturation of the structurally homologous proteins lysozyme and -lactalbumin has been studied in the presence of these salts. Significant thermal stabilization of hen egg-white lysozyme has been observed in the presence of sodium acetate and sodium sulfate. However, the thermal stabilization observed for -lactalbumin is very small in the presence of these salts and sodium thiocyanate leads to a lowering of its thermal denaturation temperature. The rise in the surface tension of aqueous salt solutions with salt concentration has been correlated with the calorimetric and volumetric measurements. The results show that V
2,m
0(tr) depends less on the type of electrolyte than on the ionic strength of the solution. The V
2,m
0(tr) values correlate very well with the increase in the surface tension of aqueous salt solutions, indicating significant role of surface tension in interactions of amino acids, peptides, or protein with the salts. 相似文献
123.
以紫外光谱法研究了青霉素G钾盐(Pen-K)在十六烷基三甲基溴化铵(CTAB)胶束体系中的水解反应, 并探讨了水解反应机理.结果表明, CTAB胶束对Pen-K的水解具有抑制作用; Pen-K在CTAB胶束体系水解时,体系pH值的变化与在水中相似, 表明H+浓度对这种抑制作用影响较小.红外光谱和微极性研究表明,部分Pen-K钾盐定位于CTAB胶束栅栏层中, 增加了其稳定性. 相似文献
124.
Eri Yoshida Kazuaki Nakamura Toshikazu Takata Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1993,31(6):1505-1512
Oxoaminium salt ( 1 ), derived from 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, 2 ) by one-electron oxidation, could be an initiator for cationic polymerization of vinyl monomers such as isobutyl vinyl ether (IBVE), 2,3-dihydrofuran, p-methoxystyrene, N-vinyl pyrrolidone, etc., to give the corresponding polymers, when 1 had a low nucleophilic counter anion. Formation of the adducts of 1 and IBVE as well as 1H-NMR and IR data suggested the formation of polymers containing N? O? C structure as the polymer head group. In the polymerization of IBVE, the effects of solvent and concentration of 1 were little observed, however the polymerization rate was dependent on temperature. Furthermore, the thermal reaction of the polymers obtained, which were regarded as prepolymers for block copolymerization and polymeric initiators for radical polymerization, was studied. For example, poly(2-benzylidene-1,3-dioxane) obtained by the polymerization of 2-benzylidene-1,3-dioxane with oxoaminium hexafluoroantimonate ( 1, X = SbF6) was employed as an initiator for radical polymerization of MMA to give its block copolymer with PMMA. © 1993 John Wiley & Sons, Inc. 相似文献
125.
CHANG Kai-Guo LU Xiang-Ping DU Fu-Ying ZHAO Min-ShouChangchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin China 《中国化学》1994,(6)
The apparent standard potential of Dy/Dy(III) system in the LiCl-KCl eutectic has been determined by the logarithmic analysis of the semi-integrals of voltammograms, logarithmic analysis of chronopotentiograms and the open circuit potentiometry. The dysprosium equilibrium potentiab for various concentration of dysprosium chloride in the LiCl-KCl eutectic melt between 400-500℃ were first determined experimentally, and the apparent standard potential of this system and its temperature dependance have been calculated. 相似文献
126.
Different physical chemical methods were used to study the thermochemical processes in a system involving a natural phosphate and complex acid salts of ammonium sulphate. The products of decomposition of the double ammonium salt and the products of their interactions with the phosphate were identified. The formation of ammonium and calcium polyphosphates and the disproportionation of P3O 10 5? and P2O 7 4? to PO 4 3? and PO 3 ? were found to depend on the circumstances of the thermal interactions. 相似文献
127.
Dr. Valentin Radtke Niklas Gebel Denis Priester Andreas Ermantraut Monika Bäuerle Dr. Daniel Himmel Regina Stroh Prof. Thorsten Koslowski Prof. Ivo Leito Prof. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(40):e202200509
Utilizing the “ideal” ionic liquid salt bridge to measure Gibbs energies of transfer of silver ions between the solvents water, acetonitrile, propylene carbonate and dimethylformamide results in a consistent data set with a precision of 0.6 kJ mol−1 over 87 measurements in 10 half-cells. This forms the basis for a coherent experimental thermodynamic framework of ion solvation chemistry. In addition, we define the solvent independent - and the values that account for the electronating potential of any redox system similar to the value of a medium that accounts for its protonating potential. This scale is thermodynamically well-defined enabling a straightforward comparison of the redox potentials (reducities) of all media with respect to the aqueous redox potential scale, hence unifying all conventional solvents′ redox potential scales. Thus, using the Gibbs energy of transfer of the silver ion published herein, one can convert and unify all hitherto published redox potentials measured, for example, against ferrocene, to the scale. 相似文献
128.
129.
130.
Maria Cyfert Barbara Latko Maria Wronska 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):619-626
The influence of NaClO4, NaCl and Na2SO4 on the oxidation of Fe(phen)
3
2+
by Ce(IV) was investigated by means of the stopped-flow method. At the concentrations range of NaClO4 and NaCl 0.1–1.0M the rate constant values decrease from 1.03·105 to 0.56·105M–1s–1 and from 1.08·105 to 0.81·105M–1s–1 respectively.In varying concentrations of Na2SO4 solutions (0.05–0.35M) the rate constant values decrease from 1.05·105M–1s–1 to 0.45·105M–1s–1.Taking into account the negative salt effect the mechanism of the reaction progress is proposed. 相似文献