Thermodynamic properties of the silver ion in alcohol + water solvent mixtures from electromotive force measurements and thermodynamic solubility product constants of AgX (X = Cl,Br, I or CNS) at different temperatures

The standard potentials of the silver-silver ion electrode in alcohol+water solvent mixtures containing 10 and 20 wt% methanol, ethanol, 1-propanol and 2-propanol have been determined from the electromotive force measurements of the cell Ag(s), AgCl(s), NaCl(c), NaNO₃(c)// NaNO₃(c), AgNO₃(c), Ag(s) at seven different temperatures in the range 5–35°C. The standard potentials in each solvent have been represented as a function of temperature. The standard thermodynamic functions for the electrode reaction, the primary medium effects of various solvents upon Ag⁺, and the standard thermodynamic quantities for the transfer of 1 g-ion of Ag⁺ from water to the respective alcohol + water media have been evaluated and discussed in the light of ion-solvent interactions as well as the structural changes of the solvents. From the values of the standard potentials of the Ag/Ag⁺ and Ag/AgX, X^? electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide, silver iodide and silver thiocyanate have been determined in alcohol + water solvent mixtures at different temperatures.     

Absolute electrode potential and thermodynamics of single ions

A new method, relating the electrode potential to the radius of the solvated ion on whose activity the potential depends, has been developed for the determination of absolute electrode potentials and the thermodynamics of single ions in solution. It is successfully applied to the cells: Pt|H₂(g, 1 atm)|HX, solvent |AgX|Ag, and M|MX, solvent|AgX|Ag, in aqueous, partially aqueous, and non-aqueous solvents. The absolute electrode potentials have been computed in aqueous and methanol+water solvents. The single ion activities, activity coefficients, the radii of solvated cations, and their solvation extent have been calculated. The temperature variation of the standard absolute potential has been utilized to evaluate the standard thermodynamic functions for the electrode reactions, and the standard transfer thermodynamic quantities of single ions from water to methanolic solvents. The results are interpreted in terms of ion—solvent interactions as well as the structural features and the acid—base properties of these solvents.     

Thermodynamics of silver salicylate in water and water + 10, + 20, and + 40 mass percent of dioxane at different temperatures

The solubility studies on silver salicylate at different temperatures were made to derive (a) the standard electrode potential of the silver—silver salicylate electrode, (b) the mean activity coefficient of silver salicylate, (c) the dissociation constant of salicylic acid, and (d) the standard thermodynamic quantities, ΔG⁰_t, ΔH⁰_t, ΔS⁰_t, and δC⁰_pt, for the transfer of silver salicylate from the standard state in water to the standard state in water + 10, + 20, and + 40 mass percent of dioxane. The results are discussed in terms of the preferential solvation of the ions.     

The stereochemistry of quaternary N-methyl sparteinium cations, their derivatives, stereoisomers and analogues : Part II. Molecular and crystal structure, and IR spectra of methiodide and methperchlorate of 2-oxosparteine

The crystal and molecular structures of two quarternary salts of 2-oxosparteine (II), the methiodide (IICH⁺₃ • I⁻) and the methperchlorate (IICH⁺₃ • ClO⁻₄) have been determined on the basis of X-ray and IR data. The studies were performed by analogy to previously investigated quaternary salts of sparteine (I), the methiodide (ICH⁺₃ • I⁻) and the methperchlorate (ICH⁺₃ • ClO⁻₄). As expected, the configurations and conformations of cationic parts within the two pairs of quaternary salts are identical, except for the structure of their A/B fragments, which in ICH⁺₃ cations have the character of tertiary amines, but in IICH⁺₃ that of lactams.

On the basis of accumulated X-ray and IR data the similarities and differences in the modes of interaction of perchlorate and iodide anions with quaternary cations, and especially with their N⁺---CH₃ groups are discussed. In this discussion are also included the methiodide and methperchlorate of -isosparteine: IIICH⁺₃ • X⁻ (X⁻ = I⁻ or ClO⁻₄) where N⁺---CH₃ groups are cisoidally oriented to the basic nitrogen atoms. The most interesting observations are as follows: (i) When N⁺---CH₃ groups are easily accessible for direct quasi hydrogen bonding interactions with counter anions and when other positive charged groups, for instance lactam groups, are absent in quaternary cations, perchlorate anions interact more strongly than the iodide anions and in consequence introduce conformational changes into the ring with N⁺---CH₃ group as well as into further rings. (ii) Perchlorate and iodide anions interact with N⁺---CH₃ groups similarly and very weakly if at all, when the N⁺---CH₃ groups are for steric reasons inaccessible to counter anions or when in quaternary cations there are additional groups which attract the counter anions electrostatically. The last mechanism operates in both quaternary salts of 2-oxosparteine and this is the reason why their monocrystals are isosteric and IR spectra almost identical. (iii) The sterically hindered N⁺---CD₃ groups in both IIICD⁺₃ • X⁻ salts give rise in their IR spectra to two doubles of sharp, well resolved bands which indicate the presence of two different rotamers stabilized by two modes of weak intramolecular hydrogen bonds with basic N atoms. (iv) In IIICH⁺₃ • X⁻ and IIICD⁺₃ • X⁻ salts the perchlorate and iodide anions do not interact at all with the rotating and vibrating N⁺---CH₃ (N⁺---CD₃) group but the structures of these salts are not isosteric since the perchlorate anions interact more strongly than iodide anions with the A/B fragment of the IIICH⁺₃ cations. This is visible from the shapes and intensities of the so-called “trans” band in the IR spectra of both salts.     

About the TATB assumption: effect of charge reversal on transfer of large spherical ions from aqueous to non-aqueous solvents and on their interfacial behaviour

We present a molecular dynamics study of the solvation properties of large spherical ions S⁺ and S⁻ of same size, in water, chloroform and acetonitrile solutions, and at a water–chloroform interface. According to the “extrathermodynamic” TATB hypothesis, such ions have identical free energies of transfer from water to any solvent. We find that this is not the case, because S⁻ interacts better than S⁺ with water (by about 20 kcal mol⁻¹), while S⁺ is better solvated by acetonitrile (by about 2 kcal mol⁻¹) and chloroform (about 8 kcal mol⁻¹) solvents. The importance of “long-range” electrostatic interactions on the charge discrimination by solvent is demonstrated by the comparison of standard vs corrected methods to calculate: (i) the electrostatic potential at the centre of the solute; (ii) the interaction energies between the ions and the solvents; and (iii) the free energies of charging the neutral sphere S⁰ to S⁺ and S⁻, respectively. These conclusions are obtained with several solvent models and simulation conditions. The question of ion pairing for the S⁺S⁻, S⁺Cl⁻ and S⁻Na⁺ pairs is also examined in the three solvents. Finally, simulations at a liquid–liquid water–chloroform interface represented explicitly, show that S⁺ and S⁻ are highly surface active, although they do not possess, like classical surfactants, an amphiphilic topology. Adsorption at the interface is found with different methodologies and at different ion concentrations. These results are important in the context of the “TATB hypothesis”, and for our understanding of solvation of large hydrophobic ions in pure liquids or in heterogeneous liquid environments.     

New aspects of the reaction of silver(I) cations with the ethylenediaminetetraacetate ion

The highly neutralized ethylenediaminetetraacetate (EDTA) titrant (95–99% as Y⁴⁻ anion) precipitates with Ag⁺ cations to form the Ag₄Y species, in aqueous medium, which is well characterized from conductometric titration, thermal analysis and potentiometric titration of the silver content of the solid. The precipitate dissolves in excess Y⁴⁻ to form a complex, AgY³⁻. Equilibrium studies at 25°C and ionic strength 0.50 M (NaNO₃) have shown from solubility and potentiometric measurements that the formation constant (95% confidence level) β₁ = (1.93 ± 0.07) × 10⁵ M⁻¹ and the solubility products are K_S0 = [Ag +]⁴[Y⁴⁻] = (9.0 ± 0.4) × 10⁻¹⁸ M⁵ and K_S1 = [Ag +]³[AgY³⁻] = (1.74 ± 0.08) × 10⁻¹² M⁴. The presence of Na⁺, rather than ionic strength, markedly affects the equilibrium; the data at ionic strength 0.10 M are: β₁ = (1.19 ± 0.03) × 10⁶ M⁻¹, K_S0 = (1.6 ± 0.4) × 10⁻¹⁹ M⁵ and K_S1 = (1.9 ± 0.5) × 10⁻¹³ M⁴; at ionic strength tending to zero; β₁ = (1.82 ± 0.05) × 10⁷ M⁻¹, K_S0 = (2.6 ± 0.8) × 10⁻²² M⁵ and K_S1 = (5 ± 1) × 10⁻¹⁵ M⁴. The intrinsic solubility is 2.03 mM silver (I) in 0.50 M NaNO₃. Well-defined potentiometric titration curves can be taken in the range 1–2 mM with the Ag indicator electrode. Thermal analysis revealed from differential scanning calorimetry a sharp exothermic peak at 142°C; thermal gravimetry/differential thermal gravimetry has shown mass loss due to silver formation and a brown residue, a water-soluble polymeric acid (decomposition range 135–157°C), tending to pure silver at 600°C, consistent with the original Ag₄Y salt.     

Thermodynamic properties of solutions of benzoic and citric acids in formamide at different tempertures

The standard thermodynamic quantities, ΔG⁰, ΔH⁰, and ΔS⁰, associated with the ionization process of benzoic acid in formamide have been evaluated. The standard potentials of the Ag(s)/AgCNS(s)/CNS⁻ and the Ag(s)/Ag₃Ci(s)/Ci³⁻ electrode, and the standard thermodynamic quantities for the electrode processes have been calculated in formamide, at different temperatures.     

Molecular motion in solid ethyltrimethylammonium halides

Proton magnetic resonance spectra have been studied over a wide temperature range for polycrystalline ethyltrimethylammonium halides [C₂H₃N(CH₃)₃]⁺X⁻, where X⁻ = Cl⁻, Br⁻ and I⁻. For the bromide and its ethyl-deuterated analogue, the proton relaxation times T₁ were also measured vs. temperature. Analysis of the experimental data yields information on the activation parameters for molecular motion within the cation and of the cation as a whole. The potential barriers determined increase as anion size decreases.     

Übergangsmetall-carbin-komplexe : LXXXIII. Neue anionische mer-dihalogeno-tricarbonyl-dialkylamino-carbin-komplexe des wolframs

The reaction of trans-X(CO)₄WCNR₂ (X = Br, R = ^c hex (cyclohexyl); X = Cl, R = ^c hex, ⁱpr (isopropyl) with M⁺X⁻ (M⁺ = NEt₄⁺, X⁻ = Br⁻; M⁺ = PPN⁺, X⁻ = Cl⁻) leads under substitution of one CO ligand to new anionic dihalo(tricarbonyl)carbyne-tungsten complexes of the type M⁺ mer-[(X)₂(CO)₃WCNR₂]⁻ (M⁺ = NEt₄⁺, X = Br, R = ^c hex; M⁺ = PPN⁺, X = Cl, R = ^c hex, ⁱ pr), whose composition and structure were determined by elemental analysis as well as by IR, ¹H and ¹³C NMR spectroscopy. In the anionic carbyne complexes the entered halogen ligand, coordinated in a cis position relative to the carbyne ligand on the metal, can be easily substituted by neutral nucleophiles, as the reaction of PPN⁺ mer-[(Cl)₂(CO)₃WCN^chex₂]⁻ with PPh₃ demonstrates yielding the neutral carbyne complex mer-[Cl(CO)₃(PPh₃)WCN^chex₂].     

Thermodynamics of the silver—silver thiocyanate electrode in urea—water mixtures

E.m.f. measurements on cells of the type Ag(s), AgCNS(s), KCNS(c)//KCl(c), AgCl(s), Ag(s) in four different composition of urea—water mixtures at seven different temperatures from 5 to 35°C have been made to determine the standard potentials of the silver—silver thiocyanate electrode in these media. These values have been used to evaluate the transfer thermodynamic quantities accompanying the transfer of 1 g ion of CNS^? ion from the standard state in water to the standard state in urea—water mixtures.     

Kinetics and mechanism of the reaction between silver(III) and thiourea in aqueous alkaline media

The tetrahydroxoargentate(III) ion, Ag(OH)₄⁻, is rapidly reduced by thiourea (tu) in accordance with the three term rate law RATE = {k₁+(k₂+k₃[OH⁻])[tu]}[Ag^III] where k₁ = 1.08 s⁻¹, k₂ = 1.46 x 10³ M⁻¹ s⁻¹, and k₃ = 2.02 x 10³ M⁻² s⁻¹. The k₁ path occurs via the rate-determining aquation of Ag(OH)₄⁻ while the other two paths involve axial attack of thiourea on silver. The higher values of k₂ and k₃ compared to the ethylenediamine reaction, which obeys the same rate law, is a reflection of the greater nucleophilicity of tu.

Following the redox reaction, solutions become brown in a reaction that obeys pseudo-first-order kinetics. Similar behaviour is observed when tu is replaced by Na₂S or thio-acetamide and when Ag^I reacts with any of these sulphur containing compounds. We attribute this process to the Ag^I promoted formation of sulphide species which eventually precipitate as Ag₂S.     

Standard potentials of the silver,silver bromide electrode and the thermodynamic properties of hydrobromic acid in 1,2-dimethoxyethane and its aqueous mixtures

The standard potentials of the silver, silver bromide electrode have been determined in 1,2-dimethoxyethane (DME) and in nineteenDME + water solvents from the e.m.f. measurements of cells of the type Pt|H₂(g, 1 atm)|HBr (m), solvent|AgBr|Ag at intervals of 5°C from 5 to 45°C. The molality of HBr covered the range from 0.01 to 0.1 mol kg^–1. In solvents of highDME content, where the dielectric constant is small, it was necessary to correct for ion-pair formation. The temperature variation of the standard potential has been used to evaluate the standard thermodynamic functions for the cell reaction, and the standard quantities for the transfer of HBr from water to the respective solvents. The results have been discussed both in relation to the acid-base nature of the solvent mixtures and also their structural effects on the transfer process.

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Standardpotentiale der Silber, Silberbromid-Elektrode und thermodynamische Eigenschaften von H Br in 1,2-Dimethoxyethan und 1,2-Dimethoxyethan—Wasser-Mischungen

Zusammenfassung Die Standardpotentiale der Silber, Silberbromid-Elektrode wurden in 1,2-Dimethoxyethan (DME) und in 19 verschiedenenDME—Wasser-Gemischen aus EMK-Messungen der Zelle Pt|H₂(g,1 atm)|HBr (m), Lsgsm.|AgBr|Ag in Temperaturintervallen von 5°C zwischen 5 und 45°C bestimmt. Die Molalität von HBr deckte den Bereich von 0,01 bis 0,1 mol kg^–1. Bei Lösungen mit höheremDME-Gehalt — und damit niedrigen Dielektrizitätskonstanten —war es nötig, für die Bildung von Ionenpaaren eine Korrektur einzuführen. Über die Temperaturvariation wurden die thermodynamischen Größen für die Zellenreaktion und die Standardgrößen für den Transfer von HBr aus Wasser in das jeweilige Lösungsmittel bestimmt. Die Ergebnisse werden sowohl im Zusammenhang zur Säure-Base-Natur de Lösungsmittelmischungen als auch in bezug auf strukturelle Effekte im Transferprozeß diskutiert.

     

Standard potentials of the silver—silver tungstate,silver—silver phosphate,and silver—silver arsenate electrodes in water—dioxane and water—urea mixtures and related thermodynamic functions

The standard potentials of the silver—silver tungstate, silver—silver phosphate and silver—silver arsenate electrodes in four different compositions of water—dioxane and water—urea mixtures at seven different temperatures from 5 to 35°C have been determined from EMF measurements of cells of the type Ag(s), AgCl(s), NaCl(c)//Na_xZ(c/x), Ag_xZ(s), Ag(s), where x is 2 or 3, and Z is WO₄, PO₄ or AsO₄. These values have been used to evaluate the transfer thermodynamic quantities accompanying the transfer of 1 g ion of WO^2?₄. PO^3?₄ or AsO^3?₄ ion from the standard state in water to the standard state in water—dioxane or water—urea mixtures.     

Predictive schemes for the reactivity of borane carbonyl and the stability of carbonyltrihydroborate anions, BH3C(O)X

The reactivity of borane carbonyl (BH₃CO) and its isoelectronic counterpart the acetylium cation (CH₃CO⁺) are compared resulting in the formulation of (carbonyl)trihydroborate anions, BH₃C(O)X⁻, which are isoelectronic and isostructural with organic carbonyls. By analogy with the ease of reduction of organic carbonyl compounds by hydroborate, the relative stability towards self-reduction-oxidation (hydride transfer from boron to carbonyl carbon) in BH₃C(O)X⁻ is proposed. The postulated order, with increasing stability is BH₃C(O)Cl⁻ < BH₃C(O)H⁻ < BH₃C(O)R⁻ < BH₃C(O)OR⁻ < BH₃C(O)NR⁻₂ < BH₃C(O)O²⁻. Experimental results of this study together with known chemistry are shown to be consistent with the proposed order. Further, it is suggested that a similar predictive scheme may be applicable to the chemistry of the amine-carboxyboranes (boron analogues of -amino acids) and their derivatives.     

Fundamental equilibrium analysis on the ion-pair extraction of dibenzo-18-crown-6 complex of alkali metal ions with picrate ion into 1,2-dichloroethane

The ion-pair extraction equilibria of dibenzo-18-crown-6 (DB18C6) complexes of Na⁺, K⁺, Rb⁺ and Cs⁺ (M⁺) with picrate ion (Pic⁻) into 1,2-dichloroethane (1,2-DCE) have been studied at 25.0°C. In the case of the Rb⁺ and Cs⁺ systems, the extraction results were interpreted by taking into consideration the formation of a (DB18C6)₂ -M⁺ complex in 1,2-DCE. The thermodynamic constants of extraction, , and ion-pair formation in 1,2-DCE, , of ion pairs of the DB18C6-M⁺ complexes with Pic⁻ were determined. By using the distribution coefficient of M⁺·Pic⁻ the thermodynamic formation constants of the DB18C6-M⁺ complexes in 1,2-DCE, , were evaluated. Consequently the component equilibrium constants of the ion-pair extraction were completely determined and a contribution of these constants to the difference of value was discussed. The value in 1,2-DCE is quite high compared with that in solvating solvents and log decreases linearly with increasing Gutmann donor number of solvents.     

Applicability of 0.05 mol kg potassium hydrogen phthalate as reference value pH standard in water–organic solvent mixtures

The applicability of 0.05 mol kg⁻¹ potassium hydrogen phthalate (KHPh(S), S=the solvent under study) as reference value pH standard (RVS) was studied in water–organic solvent mixtures. Phthalic acid in various aqueous organic solvent mixtures was titrated potentiometrically with Bu₄NOH (MeOH), using a pH-ISFET and a glass electrode as pH-sensors, and the buffer capacity of the HPh⁻ solution was roughly estimated from the difference between the first and second half-neutralization potentials. The influence of potassium ion to the buffer capacity was also studied, titrating KHPh and Et₄NHPh with CF₃SO₃H and Bu₄NOH (MeOH) and comparing the titration curves. The KHPh solution loses its buffer capacity if the solvent mixture has an aprotic property. For aqueous mixtures of protophilic aprotic solvents (e.g. DMSO and DMF), it is unsuitable as RVS if the water content is less than ca. 40 (v/v)%. The necessity of selecting subsidiary pH standard(s) is suggested for the solvent systems in which KHPh is inapplicable.     

Selective transport of silver ions through bulk liquid membrane using Victoria blue as carrier

Transport of Ag⁺ as Ag(CN)₂⁻ ions through a bulk liquid membrane is reported. The bulk liquid membrane used is a solution of Victoria blue (VB) in chloroform. The effects of pH of the source phase, cyanide concentration in the source phase, sodium hydroxide in the receiving phase, and VB concentration in the organic phase on the efficiency of the transport system were studied. The above system has a high selectivity for Ag⁺ and can selectively and efficiently transport Ag(CN)₂⁻ ion from aqueous solutions containing other cations such as alkali and alkaline earths, Zn²⁺, Pd²⁺, Cu²⁺, Cd²⁺,Hg²⁺, Co²⁺, Fe²⁺, Pb²⁺, Ni²⁺, and Al³⁺.     

Solvent effect on K to Na ion mutation: a Monte Carlo simulation study

Monte Carlo simulation studies of statistical perturbation theory (SPT) have been carried out to investigate the solvent effects on the relative free energies of solvation and the difference in partition coefficients (log P) for K⁺ to Na⁺ ion mutation in the several solvents. We compared the relative free energies for interconversion of K⁺ to Na⁺, in H₂O (TIP4P) in this study with those published works, that in H₂O (TIP4P) is −16.55 kcal/mol in this study, those of the published works are −17.6, −17.3 and −17.31 kcal/mol and that of the experiment is −17.6 kcal/mol, respectively. Comparing the relative free energies for interconversion of K⁺ to Na⁺, in CH₃OH in this study with those published works, that in CH₃OH is −18.08±0.28 kcal/mol in this study, that of molecular dynamic simulation is −19.6±0.4 kcal/mol and that of the experimental work is −17.3 kcal/mol, respectively. There is good agreement among the several studies if we consider both methods of obtaining the solvation (or hydration) free energies and the standard deviations. For the present K⁺ and Na⁺ ions, the relative free energies of solvation vs Born's function of solvents are decreased with increasing Born's function of solvent except for CH₃OH, THF and MEOME. There is also good agreement between the calculated structural properties in this study and the computer simulation, ab initio and experimental works.     

漂白过程的电化学研究——Ⅱ.碘离子对Fe(Ⅲ)络合物氧化金属银反应的影响

当溶液中含有溴化物时,Fe(Ⅲ)络合物与银电极之间的反应较慢。如果使用碘化物、反应会加快。电流加和原理和溶度积常数可用来解释碘化物对Fe(Ⅲ)络合物氧化金属银反应加速作用机理。在电极表面上氧化形成的AgI较之溴化银更难用硫代硫酸盐络合除去。 在含有Fe(Ⅲ)络合物的溴化物和碘化物混合溶液中,卤化银在银电极表面上的生成速率随溶液中碘化物浓度的增大先是下降,然后上升。因为AgI较低的溶度积常数,AgI/Ag的阳极化曲线与Fe(Ⅲ)络合物/Fe(Ⅱ)络合物氧化还原对的阴极化曲线间较负的混合电位,在浸入含有少量碘化物和一定浓度溴化物的Fe(Ⅲ)络合物溶液的银电极表面上,优先生成AgI。     

Role of axial ligation on potentiometric response of Co(III) tetraphenylporphyrin-doped polymeric membranes to nitrite ions

Two types of Co(III) tetraphenylporphyrins, Co(III)TPPX (I) and Co(III)(N)TPPX (II), where X = C1⁻ or NO⁻₂ and N = C₅H₅N or C₆H₅CH₂C₅H₄N, are used as ionophores to prepare nitrite responsive polymeric membrane electrodes. The influence of the initial axial ligand (X⁻ and N) on the operative ionophore mechanism of these metalloporphyrins within the solvent polymeric membranes is examined. Results from potentiometric and electrodialysis experiments suggest that in the presence of nitrite in the test sample and internal solution, both types of Co (III) porphyrins studied (I and II) act as neutral carriers and that the addition of lipophilic cationic sites (e.g., tridodecylmethylammonium ions (TDMA⁺)) to the organic membrane is essential to improve the selectivity and long term stability of sensors prepared with these species. Membranes formulated with (I) or (II) in the nitrite form along with TDMACl in plasticized PVC films exhibit the following selectivity sequence: SCN⁻ > NO⁻₂ ˜ C1O⁻₄ > Sal⁻ > NO⁻₃ > Br⁻ > C1⁻. Membrane electrodes with added lipophilic cationic sites are shown to exhibit rapid, fully reversible and Nernstian response towards nitrite ions in the concentration range of 10⁻¹–10⁻⁵ M, with good long term stability.