共查询到20条相似文献,搜索用时 15 毫秒
1.
Wang X Li Y Li J Wang J Wang Y Guo Z Yan H 《The journal of physical chemistry. B》2005,109(21):10807-10812
The complex formation between sodium carboxymethylcellulose (NaCMC) and dodecyltrimethylammonium bromide (DTAB) at various sodium bromide concentrations (C(NaBr)) has been studied by microcalorimetry, turbidimetric titration, steady-state fluorescence measurements, and the fluorescence polarization technique. The addition of salt is found to influence the formation of NaCMC/DTAB complexes markedly. At C(NaBr) = 0.00, 0.01, 0.02, 0.10, and 0.20 M, DTAB monomers form micelle-like aggregates on NaCMC chains to form NaCMC/DTAB complexes above the critical surfactant concentration (C1). At C(NaBr) = 0.23 M, DTAB molecules first form micelles above a 2.46 mM DTAB concentration prompted by the added salt, and then, above C1 = 4.40 mM, these micelles can aggregate with NaCMC chains to form NaCMC/DTAB complexes. However, at C(NaBr) = 0.25 M, there is no NaCMC/DTAB complex formation because of the complete salt screening of the electrostatic attraction between DTAB micelles and NaCMC chains. It is also surprisingly found that the addition of NaBr can bring out a decrease in C1 at C(NaBr) < 0.20 M. Moreover, the addition of NaBr to a mixture of 0.01 g/L NaCMC and 3.6 mM DTAB can directly induce the formation of NaCMC/DTAB complexes. This salt-enhancing effect on the complex formation is explained as the result of competition between the screening of interaction of polyelectrolyte with surfactant and the increasing of polyelectrolyte/surfactant interaction owing to the growth of micelles by added salt. When the increasing of polyelectrolyte/surfactant interaction exceeds the screening of interaction, the complex formation can be enhanced. 相似文献
2.
The heats of reaction of zinc(II) with glycylglycine at temperatures 288.15, 298.15, and 308.15 K and ionic strengths 0.25,
0.50, and 0.75 (potassium nitrate as a supporting electrolyte) were determined by calorimetry. The thermochemical results
were processed with inclusion of stepwise equilibria. In addition to complexation reactions, “side” protolytic processes were
considered. Standard heats of complexation in the system were found by extrapolation to the zero ionic strength by an equation
with one individual parameter. The influence of the supporting electrolyte concentration and temperature on the thermodynamic
characteristics of the complexation reactions in the glycylglycine-zinc(II) system was considered. The standard enthalpies
of formation of ZnGlyGly+, Zn(GlyGly)2, and Zn(GlyGly)3− species in aqueous solution were calculated. 相似文献
3.
Wang X Wang J Wang Y Yan H 《Langmuir : the ACS journal of surfaces and colloids》2004,20(21):9014-9018
Salt effect on the interaction of anionic polyelectrolyte sodium carboxymethylcellulose (NaCMC) with cationic gemini surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)6N(CH3)2C12H25]Br2 (C12C6C12Br2) has been investigated using turbidimetric titration, steady-state fluorescence, and mobility measurement. It is found that the critical aggregation concentration(cac) for C12C6C12Br2/NaCMC complexes depends little on addition of sodium bromide (NaBr). However, in the presence of nonionic surfactant Triton X-100 (TX100), the critical ionic surfactant mole fraction for the onset of complex formation (Yc) increases markedly with increasing NaBr concentration. These salt effects are supposed as the overall result from competition between the increase of interaction and the screening of interaction. The increase of interaction is referred to as the effect that the larger micelle with higher surface charge density induced by salt has a stronger interaction with oppositely charged polyelectrolyte. The screening of interaction is referred to as the salt screening of electrostatic attraction between the polymer chain and the surfactant. For complex formation between C12C6C12Br2 and NaCMC, the increase of interaction probably compensates the screening of interaction, leading to constant cac values at different salt concentrations. For complex formation between the C12C6C12Br2/TX100 mixed micelle and NaCMC, the screening of interaction probably plays a dominant role, leading to higher suppression of electrostatic binding of micelles to polyelectrolyte. 相似文献
4.
L. A. Kochergina E. L. Ratkova G. G. Gorboletova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(4):549-555
The heat effects of complex formation between D,L-threonine and zinc(II) ions at 288.15, 298.15, and 308.15 K and ionic strengths of 0.25, 0.50, and 0.75 were determined calorimetrically against the background of potassium nitrate. The thermochemical results were processed taking step equilibria into account. Along with complex formation, side protolytic processes were considered. The standard heat effects of complex formation in the system studied were determined by extrapolation to zero ionic strength with the use of an equation with one individual parameter. The heats of solution of D,L-threonine in water and aqueous alkali were used to calculate the standard enthalpies of formation of the complexes. 相似文献
5.
Pártay LB Jedlovszky P Brovchenko I Oleinikova A 《Physical chemistry chemical physics : PCCP》2007,9(11):1341-1346
Formation of the macroscopically-infinite hydrogen-bonded water network in various aqueous systems occurs via 3D percolation transition when the probability of finding a spanning water cluster exceeds 95%. As a result, in a wide interval of water content below the percolation threshold, rarefied quasi-2D water networks span over the mesoscopic length scale. Formation and topology of spanning water networks, which affect various properties of aqueous systems, can be described within the framework of the percolation theory. 相似文献
6.
Partial molal volume changes during complex formation between SCN–, I–, and ClO4
– -and -cyclodextrin have been determined by two independent methods of measurements; one based on density measurement and subsequent calculation of apparent molal volumes, the other on differentiating the association constants with respect to pressure. Results from the two methods are in good agreement.Negative volume changes were observed for complex formation between the anions and -cyclodextrin while zero or slightly positive values were observed for complex formation with -cyclodextrin. The result is consistent with the idea that the anions do not become dehydrated as they form complexes with cyclodextrins. 相似文献
7.
L. A. Kochergina A. V. Emel’yanov O. N. Krutova 《Russian Journal of Inorganic Chemistry》2008,53(9):1526-1530
The heats of complex formation in the L-phenylalanine-copper(II) ion system in aqueous solution were determined calorimetrically at 288.15, 298.15, and 308.15 K for an ionic strength of 0.5 (KNO3 supporting electrolyte). The thermodynamic parameters of formation of phenylalaninatocopper(II) complexes were calculated for various temperatures. 相似文献
8.
9.
L. A. Kochergina O. V. Platonycheva O. M. Drobilova V. V. Chernikov 《Russian Journal of Inorganic Chemistry》2009,54(2):332-339
Heats of reactions between a nickel(II) ion and β-alanine were measured calorimetrically at 288.15, 298.15, and 308.15 K and
ionic strengths of 0.5, 1.0, and 1.5 (KNO3). Thermochemical data were processed with account for stepwise equilibria; attendant protolytic processes were taken into
account together with complexing reactions. Extrapolation to the zeroth ionic strength with the use of a one-parameter equation
gave standard thermodynamic characteristics of complex formation in the system. The influence of the supporting electrolyte
and temperature on the heats of complex formation reactions was considered. Standard enthalpies of formation were calculated
for NiAla+, NiAla2, and NiAla3− species.
Original Russian Text ? L.A. Kochergina, O.V. Platonycheva, O.M. Drobilova, V.V. Chernikov, 2009, published in Zhurnal Neorganicheskoi
Khimii, 2009, Vol. 54, No. 2, pp. 377–384. 相似文献
10.
The abilities of multifunctional polyelectrolytes to enhance aluminum hydroxide dispersion and inhibit silica scale formation were examined in a pilot cooling water system. The following multifunctional polyelectrolytes were studied: a terpolymer of acrylic acid (AA), 2-acrylamide-2-methyl propane sulfonic acid (SA) and N-vinylpyrrolidone (NVP) (P(AA/SA/NVP)), acrylic acid homopolymer (P(AA)) and a copolymer of AA and SA (P(AA/SA)). The order of inhibition ability was P(AA/SA/NVP)>P(AA/SA)>P(AA), and was consistent with that of the dispersing ability for aluminum hydroxide. Other terpolymers incorporating different nonionic monomers were also examined and factors affecting their inhibition abilities were investigated, based on interaction energies calculated by density functional theory. Based on the correlation between scale inhibition abilities and interaction energies, we elucidated that the effective nonionic monomer of terpolymer for silica scale inhibition had low affinity for aluminum hydroxide and high affinity for H(2)O and Si(OH)(3)O(-). The affinities of nonionic monomer for aluminum hydroxide and H(2)O suggested that there was proper conformation of polyelectrolyte adsorbed for effectively dispersing aluminum hydroxide. Also, high affinity of nonionic monomer for Si(OH)(3)O(-) suggested that interacting Si(OH)(3)O(-) is an important role of inhibition of silica scale formation. 相似文献
11.
Polyelectrolyte complexes have been elaborated by mixing in water neutral poly(beta-CD), a cationic surfactant (DTAC) and herring sperm DNA fragments. The driving forces for the poly(beta-CD)/DTAC/DNA association in aqueous solution are, on the one hand, reversible inclusion interactions between the CD cavities of poly(beta-CD) and the alkyl group of DTAC, leading to the formation of a polycation and, on the other hand, electrostatic interactions between the opposite charges of the cationic surfactant and anionic DNA. Viscometry and SANS have been used to prove the occurrence of such ternary complexes in dilute aqueous solutions. 相似文献
12.
V. Yu. Kurochkin V. V. Chernikov T. D. Orlova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(4):598-602
Complex formation of L-leucine with calcium ions in aqueous solution was studied by potentiometric titration at 298.15 K and
ionic strength values I = 0.5, 1.0, and 1.5 (KNO3). The formation of the CaL+ and CaHL2+ complex particles was established and their stability constants were determined. The enthalpies of protolytic equilibria
of leucine and formation of calcium ion complexes with leucine were determined calorimetrically at 298.15 K and I = 0.5 (KNO3). The thermodynamic characteristics of complex formation between calcium ions and L-leucine were calculated. 相似文献
13.
Bühl M 《Inorganic chemistry》2005,44(18):6277-6283
Static geometry optimizations and Car-Parrinello molecular dynamics simulations with the BP86 density functional, as well as NMR chemical shift calculations at the GIAO-B3LYP level, have been used to assess structure, speciation, and dynamics of aqueous solutions of the vanadate-glycylglycine complex. According to the simulations, this complex should be formulated as five-coordinate, anionic [VO2(GlyGly')]- (GlyGly' = H2N-CH2-C(O)-N-CH2-CO2). The neutral conjugate acid is unstable in water, where it is deprotonated within a few picoseconds. Six-coordinate structural alternatives, [VO(OH)2(GlyGly')]-, are disfavored energetically and/or entropically. The hydration shell around [VO2(GlyGly')]- in water is characterized in terms of suitable pair correlation functions. 相似文献
14.
Experimental solubilities of amorphous silica in several aqueous electrolyte solutions and in aqueous solutions of organic compounds, and theoretical considerations concerning cavity formation, electrostriction collapse, ion solvation, and long- and short-range interaction of the solvated ions with one another(1) permit the calculation of the partial excess free energies and the activity coefficients of aqueous silica. It is shown that, in the case of non-dissociated aqueous organic solutions, the variation of log m (SiO2) with the reciprocal of the dielectric constant of the solution is described by a single linear equation independent of the nature of the organic compound. For aqueous electrolyte solutions, a specific linear relationship between log m (SiO2) and the reciprocal of the dielectric constant occurs for each electrolyte. The success of the equation in reproducing the experimental solubilities of amorphous silica in aqueous solutions of electrolytes and organic compounds supports previous evidence indicating a polar charge distribution in the solvated SiO2 molecule. Our data permit the calculation of the effective local charge of dissolved SiO2 molecules and of the short-range interaction parameters between SiO2 and various ions. The proposed equation of state can be used to calculate the affinity of reactions among SiO2 minerals and complex aqueous solutions. 相似文献
15.
Sastri CV Sook Seo M Joo Park M Mook Kim K Nam W 《Chemical communications (Cambridge, England)》2005,(11):1405-1407
A mononuclear nonheme oxoiron(IV) complex bearing a pentadentate N5 ligand was prepared in aqueous solution; the pH dependence of its stability and reactivities was reported along with the mechanistic details of sulfide oxidation by the oxoiron(IV) species. 相似文献
16.
A model of the specific acid-catalyzed glycosidic bond formation in liquid water at ambient conditions is studied based on constrained Car-Parrinello ab initio molecular dynamics. Specifically the reaction of alpha-D-glucopyranose and methanol is found to proceed by a D(N)A(N) mechanism. The D(N) step consists of a concerted protonation of the O(1) hydroxyl leaving group; this process results in the breaking of the C(1)-O(1) bond, and oxocarbenium ion formation involving C(1)=O(5). The second step, A(N), is the formation of the C(1)-O(m) glycosidic bond, deprotonation of the methanol hydroxyl group O(m)H(m), and re-formation of the C(1)-O(5) single bond. A focus of this study is the analysis of the electronic structure during this condensed phase reaction relying on both Boys/Wannier localized orbitals and the electron localization function ELF. This analysis allows the clear elucidation of the chemical bonding features of the intermediate bracketed by the D(N) and A(N) steps, which is a non-solvent equilibrated oxocarbenium cation. Most interestingly, it is found that the oxygen in the pyranose ring becomes "desolvated" upon double bond/oxocarbenium formation, whereas it is engaged in the hydrogen-bonded water network before and after this period. This demonstrates that hydrogen bonding and thus the aqueous solvent play an active role in this reaction implying that microsolvation studies in the gas phase, both theoretical and experimental, might lead to qualitatively different reaction mechanisms compared to solution. 相似文献
17.
The protonation of 1,2,3-propanetricarboxylate (tricarballylate, tca) was studied in LiCl, NaCl, KCl, MgCl(2), CaCl(2) and tetraethylammonium iodide (Et(4)NI) aqueous solutions, at 25 degrees C, in the ionic strength range 0 < I < 1M, using the pH-metric technique. The differences between protonation constants determined in Et(4)NI and those determined in the other background salts were interpreted in terms of complex formations. Least squares calculations are consistent with the formation of MLH(j) (j = 0,1.2), M(2)LH(i) (i = 0,1,2), M(2)L species, when M = Mg(2+), Ca(2+). Potentiometric measurements performed in mixed NaClKCl, NaClCaCl(2) and MgCl(2)CaCl(2) solutions showed the formation of mixed metal complexes NaKL, NaKHL, NaCaL and CaMgL. The dependence on ionic strength of protonation and complex formation constants was evaluated using a simple Debye-Hückel type equation. 相似文献
18.
Kazunori Odashima Akiko Itai Yoichi Iitaka Yoji Arata Kenji Koga 《Tetrahedron letters》1980,21(45):4347-4350
NMR studies (1H and 13C) demonstrating an inclusion complex formation in a particular geometry between a water-soluble paracyclophane, CP44, and hydrophobic substrates in acidic aqueous solution are described. 相似文献
19.
Alessandro De Robertis Claudia Foti Antonio Gianguzza Carmelo Rigano 《Journal of solution chemistry》1996,25(6):597-606
The protonation of 1,10-phenanthroline has been studied potentiometrically in different aqueous salt media (LiCl, NaCl, KCl, Me4NCl, Et4NI, MgCl2, CaCl2, SrCl2, and BaCl2) in the ionic strength range 0≤1≤1 M. This ligand forms two protonated species, [H(phen)]+ and [H(phen)2]+; the monoligand species shows protonation constants strongly dependent on the medium. Medium effects were explained by the formation of some weak species: [H(phen)Cl]0, [M(phen)]2+ (M=alkaline earth metal cations). Formation thermodynamic parameters are reported. 相似文献
20.
G. G. Gorboletova A. A. Metlin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(5):763-766
Heat effects of the interaction of copper(II) solutions with aminoacetic acid (glycine) are measured by the direct calorimetry at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 against a background of potassium nitrate. Standard enthalpy values for reactions of the formation of aminoacetic acid copper complexes in aqueous solutions are obtained using an equation with a single individual parameter by extrapolating it to zero ionic strength. The standard thermodynamic characteristics of complex formation in the Cu2+-glycine system are calculated. It is shown that glycine-like coordination is most likely in Cu(II) complexes with L-asparagine, L-glutamine, and L-valine. 相似文献