Water vapor nucleation on ion pairs under the conditions of a planar nanopore

Computer simulation has been employed to study the effect of a confined space of a planar model pore with structureless hydrophobic walls on the hydration of Na⁺Cl^– ion pairs in water vapor at room temperature. A detailed many-body model of intermolecular interactions has been used. The model has been calibrated relative to experimental data on the free energy and enthalpy of the initial reactions of water molecule attachment to ions and the results of quantum-chemical calculations of the geometry and energy of Na⁺Cl^– (H₂O)_N clusters in stable configurations, as well as spectroscopic data on Na⁺Cl^– dimer vibration frequencies. The free energy and work of hydration, as well as the adsorption curve, have been calculated from the first principles by the bicanonical statistical ensemble method. The dependence of hydration shell size on interionic distance has been calculated by the method of compensation potential. The transition between the states of a contact (CIP) and a solvent-separated ion pair (SSIP) has been reproduced under the conditions of a nanopore. The influence of the pore increases with the hydration shell size and leads to the stabilization of the SSIP states, which are only conditionally stable in bulk water vapor.     

Solvent Extraction of Selenate and Chromate Using a Diaminocalix[4]arene

The extraction of Se(VI) and Cr(VI) using a diammoniumcalix[4]arene was investigated. A study of parameters such as ligand concentration, pH or diluent was carried out and allowed to specify the stoichiometry of the extracted species. It was shown that Se(VI) is extracted into CHCl₃ as (LH₂ ²⁺, Cl^-, HSeO₄ ^-) and ((LH₂ ²⁺)₂, 2Cl^-, SeO₄ ^2-)species at pH 2.6. An increase of pH or an addition of 5% or 10% decanol in CHCl₃ favors the extraction of SeO₄ ^2- over HSeO₄ ^- but leads to a drastic decrease of seleniumextraction. Cr(VI) was shown to be extracted as(LH₂ ²⁺, Cl^-, HCrO₄ ^-) at pH 2.6 and probably as (LH⁺, HCrO₄ ^-) for higher pH.     

计算机模拟阴离子对碳酸镍结晶过程的影响

本文采用原子模拟技术,研究了不同溶液中碳酸镍的结晶行为。结果表明,水化作用使碳酸镍晶体更稳定,形貌更规整。杂质阴离子SO₄^2-与碳酸镍晶体表面的作用力较强,但对其形貌影响不大。Cl^-对表面的作用力较弱,但使晶体形貌更不规则。在模拟的几种情况中,碳酸镍的(104)晶面均是最主要的显露面。模拟结果能与实验现象很好吻合。     

Ab initio MO study of selected aluminum and boron chlorides and fluorides: Comparison with 11B NMR spectra of a tetrachloroborate melt

Molecular geometries were fully optimized for AlCl₃, AlCl₄^-, Al₂Cl₆, Al₂Cl₇^-, AlF₃, AlF₄^-, Al₂F₆, Al₂F₇^-, BCl₃, BCl₄^-, B₂Cl₆, B₂Cl₇^-, BF₃, BF₄^-, B₂F₆, and B₂F₇^-, as well as a few mixed halogen species, at the Hartree-Fock (HF) level, using basis sets from STO-3G to 6–311 + G(d). In some cases geometries were also optimized at the MP2 level. Where possible, the computed geometries were compared to known structures from electron or X-ray diffraction. The agreement between these was quite good for the neutral species, and somewhat poorer for the anions. Vibrational frequencies were calculated for all species at the HF level with the largest basis set. The geometries were characterized as minima or transition structures. Various formation reaction enthalpies were calculated; these compare well with known values. More extensive calculations on the BF₃/BF₄^- system indicate the structures and enthalpies are nearly converged with respect to basis set size and level of correlation treatment. The previously unknown species B₂Cl₇^- is predicted to be energetically stable on the basis of the calculations. Some features of the ¹¹B NMR spectra of room temperature melts consisting of mixtures of boron trichloride with 1-methyl-3-ethylimidazolium chloride are presented. These features suggest that these melts may contain small amounts of B₂Cl₇^- as an intermediate in an exchange reaction. © 1996 by John Wiley & Sons, Inc.     

Properties of the gold(I) sulfite complex in acidic chloride solutions

The effects of various factors on the redox stability of the gold(I) sulfite complex Au(SO₃)₂^3- in acidic chloride solutions is studied. Increased concentrations of gold and H⁺, as well as temperature, reduce the time before traces of gold(0) emerge; increased concentrations of sulfite and especially of Cl^– increase this time. The beaker material (quartz, glass, or polypropylene) is found to have no significant effect. Added organic solvents have different effects. It is shown using UV spectroscopy and pH measurements that the average number of SO₃^2- ions bound to one gold(I) ion can be much greater than two even at an excessive amount of sulfite in the acidic region (pH 2–4) due to the equilibrium Au(SO₃)Cl^2– + SO₃^2- = Au(SO₃)₂^3- + Cl^– with the constant logK₂ = 6.4 ± 0.1 at 25°C and I = 1 M (NaCl).     

Thermogravimetric investigation on the chloride binding behaviour of MK-lime paste

The hydration products of 2.5, 5 and 10% Cl⁻ containing metakaolin (MK)-lime pastes are compared with the same obtained from MK-lime paste to understand the chloride binding behaviour of MK during the hydration of cement. Results indicate that 2.5% Cl⁻ addition into the MK-lime paste initially enhances the formation of Friedel's salt (Ca₂Al(OH)₆Cl·2H₂O), but Friedel's salt decomposes at later stages due to the formation of stratlingite (C₂ASH₈). In 5 and 10% chloride containing pastes, Friedel's salt is observed throughout the reaction periods along with the high amount of CSH. Small amount of stratlingite is also formed on or after 60 day hydration of 5% Cl⁻ containing MK-lime pastes. On the other hand, MK-lime-10% Cl⁻ containing pastes show the complete absence of stratlingite and C₄AH₁₃ through out the hydration period, which are the major hydration products of MK-lime paste. Mesuarements of pH of the simulated pore fliuds help to understand the decomposition behaviour of Friedel's salt. From the experimental results, chloride binding mechanism of MK-lime paste is also discussed.     

五氯亚硝酰合铱酸根与二苯胺反应的研究

本文主要用分光光度法研究[Ir(NO)Cl_5]-与二苯胺的反应。在6M盐酸溶液中,生成1:1及2:1配合物,吸收峰分别在515nm及571nm,摩尔吸光系数为2.3×10~4及3.8×10~4。实验表明,新配合物是由[Ir(NO)Cl_5]-的NO~+基在二苯胺氨基的对位发生亲电取代反应而生成。     

The Energy Barrier to Recombination in Hydrated Plasma

An abnormally high potential barrier that separates the H₃O⁺ and Cl^? ions in a cluster of water molecules was revealed. The profile of the barrier was calculated by computer simulation. The calculation was based on a detailed model of intermolecular interactions developed on the basis of experimental data on the free energy and entropy for the addition reactions of water molecules in the vapor phase to the hydration shell of ions in conjunction with the results of quantum-chemical calculations.     

Water vapor clustering in the field of Na<Superscript>+</Superscript> cation inside a nanopore with hydrophilic walls. 1. Spatial organization

Computer simulation has been employed to study the structure of a hydration shell of a Na⁺ ion under the conditions of a planar nanopore with structureless hydrophilic walls at 298 K. Intermolecular interactions have been described in terms of a detailed model calibrated with respect to experimental data on the free energy and enthalpy of the initial reactions of vapor molecule attachment to the ion. In the field of hydrophilic walls, the hydration shell is disrupted into an enveloping part and that spread over the surface of the walls. At the final stage of hydration, states with asymmetric distribution of molecules on opposite walls survive and the phenomenon of ion displacement out of its shell is stably reproduced. The orientational molecular order in the system strongly depends on the degree of wall hydrophilicity. The hydration shell of a sodium ion is less stable with respect to disturbances generated by the field of hydrophilic walls than the shell of a chlorine ion is.     

Hydrogen bonding between a water molecule and electronegative additives (O or Cl) on a Pt(111) surface

Water adsorption on Pt(111) surfaces treated with oxygen or hydrogen chloride at 20 K has been studied by Fourier transform infrared spectroscopy and scanning tunneling microscopy. Water molecules chemisorb predominantly on the sites of the electronegative additives (O or Cl^-), forming hydrogen bonds of O-HO or O-HCl^-. On a Pt(111)-2×2-O surface, water adsorption produces species (O(D₂O)), monomeric water (D₂O), (O(D₂O)₂) and ring tetramer-like cluster (O(D₂O)₃) on a Pt(111) surface. On a Pt(111)-3×3-Cl^- (θ=0.44) surface, water adsorption gives rise to a Pt(111)-(4×2)-(H₃O⁺+Cl^-) co-adsorption structure to form a hydrogen-bonding network between Cl^- and H₃O⁺ ions.     

Ion pairs in aqueous electrolyte microdrops under conditions of a flat nanopore

The molecular mechanisms of aqueous solvent penetration into a flat nanopore with hydrophobic structureless walls containing a Na⁺Cl^? ion pair with nonfixed distance between ions is studied by computer simulations. A detailed many-body polycenter model of intermolecular interactions calibrated with respect to experimental data for the free energy of attachment of water vapor molecules and quantum-chemical calculations in clusters is used. The ion pair hydration results in its decomposition. Drawing the molecules into the gap between ions makes easier penetration of solvent and filling of the nanopore with electrolyte. The ion-pair dissociation is accompanied by dramatic changes in the chemical potential of molecules and electric properties of the whole system. The thermodynamic characteristics of decomposition are stable as regards variations in the pore width. The post-decomposition electric polarizability demonstrates strong anisotropy associated with the nanopore flatness.     

Ion-Pair Photodissociation of Trichloromonofluoromethane

Anionic fragments, F^- and Cl^- including two isotope species ³⁵Cl^- and ³⁷Cl^-, are ob-served in the photoexcitations of CFCl₃. The ion-pair anion e±ciency spectra of ³⁵Cl^- and ³⁷Cl^- are recorded in the photon energy range of 7.75～22.00 eV. The threshold of ion-pair dissociation CFCl₃→CFCl₂⁺+Cl^- is experimentally determined to be 7.94±0.04 eV. With the references of the high-resolution photoabsorption spectra reported in the literatures, we make tentative assignments of the electron valence-to-Rydberg transitions. Furthermore, the multibody ion-pair fragmentation processes to Cl^- are discussed by comparison between the calculated thermochemical thresholds and the experimental efficiency spectrum.     

Interaction of PdCl 42- with L-cystine in hydrochloric acid solutions

The effect of acidity and equilibrium chloride ion concentration on the interaction of PdCl₄ ^2- with cystine (H₂CySS) in hydrochloric acid solutions was studied. Pd(H₄CySS)Cl₃+ complex was found to form at [Cl^–] = 1.0, 0.5, or 0.25 mol/Linthe [H⁺] range from 0.10 to 1.00 mol/L; the relevant equilibrium constant was determined. Monodentate coordination of cystine to palladium(II) through the sulfur atom was proposed on the basis of analysis of conditional stability constants as functions of [Cl^–] and [H⁺].     

高氯酸盐与十六烷基三甲基溴化铵作用的光散射

利用光散射光谱法研究了高氯酸根和阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)的作用。 在酸性条件下,高氯酸根和CTAB通过静电作用形成离子缔合物,导致体系光散射强度增强。 环境水样中的常见阴离子如Cl^-、Br^-、ClO₃^-、NO₃^-和PO₄^3-等与CTAB单独作用时其光散射强度很弱,而当它们与高氯酸根同时存在时,由于协同作用使体系散射强度发生改变。 以Cl^-为例,借助动态光散射测定,初步探讨了体系协同作用的机理。     

Adsorption phenomena on polycrystalline gold electrode modified by Zn adatoms

Summary In this paper, experimental results obtained by the in-situ radiotracer and voltammetric studies of the competitive adsorption of the HSO₄^-/SO₄^2- (labeled with ³⁵S) and Cl^- (labeled with ³⁶Cl) anions on bare Au_poly substrate and Au_poly surfaces modified by the Zn adatoms in the lower pH region (pH≤4.5) are presented and discussed. In addition, some data on the formation of Zn adlayers (labeled with ⁶⁵Zn) are reported to demonstrate the complex features of the underpotential deposition (UPD) phenomenon. It has been revealed that (1) the relative adsorption strength of Cl^- ions on bare Au_poly is higher than that of H₂PO₄^-/PO₄^3- and HSO₄^-/SO₄^2- ions in the entire pH region studied; (2) anomalous tendency of the specific adsorption of anions on polycrystalline gold modified by Zn adatoms occurs at pH 4.5 as follows: PO₄^3->SO₄^2->Cl^->>ClO₄^- and (3) the UPD of Zn²⁺ ions on polycrystalline gold is measurable even from solutions containing 5 ^. 10^-8M Zn²⁺ over the entire potential range where the hydrogen evolution takes place.It is, however, plausible to assume that the coverage of the gold surface by Zn adatoms measured even at solution concentrations of c≥5 ^. 10^-4M does not exceed one monolayer.     

Hydration numbers of ions in aqueous solutions of KOH, KCl, KI, and KIO3 according to refractometric data

Ion hydration in aqueous solutions of KOH, KCl, KI, and KIO₃ was studied by refractometry. The sum of the hydration numbers of the potassium ion and each anion in these compounds and the hydration numbers of OH^?, Cl^?, I^?, and IO ₃ ^? anions were determined by the Lorentz-Lorenz equation at different salt concentrations. The model suggests that the polarizability of the hydrated ion is proportional to the cube of the ion radius and the volume of the hydrated ion equals the sum of the nonhydated ion and hydration shell volumes. The hydration numbers of the anions calculated by the proposed procedure increase with their radii in the sequence: OH^?, Cl^?, I^?, and IO ₃ ^? .     

19F NMR study of mixed fluorohalide anions of niobium(V) and tantalum(V) in solution

Anions of the type MF_nX^-_6-n (M = Nb^V, Ta^V; X = Cl_-, Br_-), including geometric isomers, have been characterised in solution by ¹⁹F NMR spectroscopy. Thirty eight fluorine-containing complexes of tantalum of the type TaF_xCl_yBr^-_z have been found from the 46 theoretically possible. The relative stability of mixed tantalum fluorochloro and fluorobromo anions of the type TaF_nX^-_6-n has been studied.     

Enantiomer separation of rac-2,2′-dihydroxy-1,1′-binaphthyl (BNO) by inclusion complexation with racemic or achiral ammonium salts and a novel transformation of a 1:1:1 racemic complex of BNO, Me4N·Cl and MeOH into a conglomerate complex in the solid state

The complete simultaneous and mutual enantiomer resolution of 2,2′-dihydroxy-1,1′-binaphthyl (BNO) and N-(3-chloro-2-hydroxypropyl)-N,N,N-trimethylammonium chloride, Me₃N⁺CH₂CH(OH)CH₂Cl·Cl⁻ into their enantiomers by inclusion complexation between their racemates in EtOH in the presence of a chiral seed crystal is reported. The enantiomer resolution of the rac-BNO was also accomplished easily by inclusion complexation with achiral ammonium salts, N-(2-hydroxyethyl)-N,N,N-trimethylammonium chloride, Me₃N⁺CH₂CH₂OH·Cl⁻ and tetramethylammonium chloride, Me₄N⁺·Cl⁻. Inclusion complexation of the rac-BNO with Me₃N⁺ CH₂CH₂OH·Cl⁻ gave only a 1:1 conglomerate inclusion complex but not a racemic complex. Recrystallization of the rac-BNO and an equimolar amount of Me₄N⁺·Cl⁻ from MeOH (7 ml) and MeOH (15 ml) gave a 1:1:1 racemic complex, BNO·Me₄N⁺·Cl⁻·MeOH and a 1:1 conglomerate complex, BNO·Me₄N⁺·Cl⁻, respectively. Novel transformation of the former racemate into the latter conglomerate occurred by heating or by exposure to MeOH vapor in the solid state.     

The extraction of copper(II) from hydrochloric acid by solutions of tetra-n-hexylammonium chloride in ethylene dichloride

In marked contrast to the behaviour of copper(I), the extraction of copper(II) by solutions of tetra-n-hexylammonium chloride in ethylene dichloride is very small from 1.0 M chloride and although it increases with concentration it does not reach 90% until the chloride concentration exceeds 4 M. By varying such parameters as [Cl^-], [NR₄⁺Cl^-]_org. and the total amount of copper in the system, it was shown that the distribution equilibria could best be explained by postulating the presence of binuclear complexes Cu₂Cl₆^2- and Cu₂Cl₇^3- in addition to mononuclear complexes in the aqueous phase, while only mononuclear species such as NR₄₊CuCl₃^-and (NR₄⁺)₂CuCl₄^2- are extracted. A linear relationship is predicted between the reciprocal of the distribution ratio and the total amount of copper present at equilibrium in the aqueous phase and confirmed by the experimental results.     

Dimerization of Chlorocuprates in Weakly Polar Solvents

The solutions of CuCl₂ and tributylbenzylammonium chloride in chlorobenzene, which are used as catalysts for a number of processes with the participation of halogenated hydrocarbons, were studied by electronic spectroscopy in visible and UV regions. It was found that copper(II) ions occurred as two anionic chlorocuprate species (CuCl^2- ₄ and Cu₂Cl^2- ₆), which were in equilibrium, in solutions over wide ranges of concentrations and temperatures. The individual spectra of the two above chlorocuprate species were distinguished. The thermodynamic parameters of the equilibrium 2CuCl^2- ₄ Cu₂Cl^2- ₆ + 2Cl^– were calculated.