An electrochemical method for determination of the standard Gibbs energy of anion transfer between water and n-octanol

The transfer of the ions Cl⁻, Br⁻, I⁻, ClO₄⁻, SCN⁻, NO₃⁻, BF₄⁻, and (C₆H₅)₄B⁻ across the water|n-octanol (W|OC) liquid interface was studied and the standard Gibbs energies of ion transfer were determined. The ion transfer was achieved by oxidation of decamethylferrocene dissolved in a droplet of n-octanol that was attached to a graphite electrode immersed in the aqueous solutions of the respective alkali salts of the anions. The electrode reaction can be described by the equation: dmfc_(OC)+X_(W)⁻⇄dmfc⁺_(OC)+X⁻_(OC)+e⁻, where X⁻ is the transferred anion. Square-wave voltammetry at this three-phase arrangement was utilised to determine the formal potential of the decamethylferrocene/decamethylferrocenium (dmfc/dmfc⁺) couple under the condition of ion transfer across the water|n-octanol interface. For calibration the standard Gibbs energies of ion transfer have been extrapolated to octanol from the series of known data for methanol, ethanol, n-propanol, and n-butanol. All these data are consistent and the experimental dependence of the formal potentials on the standard Gibbs energies is as predicted by theory. The validity of data is further supported by calculations of Gibbs energies of ion transfer using the Born theory. Until now it was not possible to perform electrochemical measurements at the water|n-octanol interface because in the conventional four-electrode cells this interface cannot be polarised. With the new method it is now for the first time possible to determine the Gibbs energies of transfer of ions across the water|n-octanol interface. These values are of very wide use for assessing the lipophilicity of compounds in chemistry, medicine, and pharmacology.     

Stability of complex of Cs+ with valinomycin in nitrobenzene saturated with water

From extraction experiments and -activity measurements, the extraction constants corresponding to the equilibrium Cs⁺(aq)+Cl^–(aq)+L(nb)CsL⁺(nb)+Cl^–(nb) in the two-phase water-nitrobenzene system (L=valinomycin; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as log K_ex(CsL⁺, Cl^–)=2.2. Further, the stability constant of the valinomycin-cesium complex in nitrobenzene saturated with water was calculated: log _nb(Csl⁺)=10.1.     

Stability of the valinomycin - lithium complex in nitrobenzene saturated with water

Summary From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Li⁺(aq)+NaL⁺(nb) ↔LiL⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (L = valinomycin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as logK_ex(Li⁺,NaL⁺)=-1.1. Further, the stability constant of the valinomycin-lithium complex species in nitrobenzene saturated with water was calculated: logβ_nb(LiL⁺)=6.3.     

Stability of the ammonium-p-tert-butylcalix[4]arene-tetrakis (N,N-diethylacetamide) complex in nitrobenzene saturated with water

Summary From extraction experiments andg-activity measurements, the extraction constant corresponding to the equilibrium NH(aq)+NaL⁺(nb)?NH₄L⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (L = p-tert-butylcalix[4]arene-tetrakis (N,N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as logK_ex(NH,NaL⁺)=-1.8. Further, the stability constant of the p-tert-butylcalix[4]arene-tetrakis (N,N-diethylacetamide)-ammonium complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: logb_nb(NH₄L⁺)=6.7.     

Stability of complexes of alkali metal cations with dibenzo-24-crown-8 in water saturated nitrobenzene

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇄ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L=dibenzo-24-crown-8; aq=aqueous phase, nb=nitrobenzene phase) were evaluated. Further, the stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the Cs⁺Rb⁺L⁺Na⁺ order.     

Stability of complex of Na+ with 18-crown-6 in nitrobenzene saturated with water

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Na⁺(aq)+HL⁺(nb)⇆NaL⁺(nb)+H⁺(aq) taking place in the two-phase water-nitrobenzene system (L=18-crown-6; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as logK _ex (Na⁺,HL⁺)=0.1. Further, the stability constant of the 18-crown-6-sodium complex in nitrobenzene saturated with water was calculated: logβ _nh(NaL⁺)=8.0.     

Stability constants of complexes of Li+, H3O+, NH 4+ and Ag+ with hexaethyl calix[6]arene hexaacetate in nitrobenzene saturated with water

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇔ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺ = Li⁺, H₃O⁺, NH₄⁺, Ag⁺; L = hexaethyl calix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were determined. Furthermore, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order H₃O⁺<NH₄⁺<Li⁺<Ag⁺.     

Solvent extraction of sodium from water into nitrobenzene by using strontium dicarbollylcobaltate in the presence of benzo-15-crown-5

Summary From extraction experiments andg-activity measurements, the extraction constant corresponding to the 2Na⁺(aq)+SrL(nb)?2NaL⁺(nb)+Sr²⁺(aq) equilibrium taking place in the two-phase water-nitrobenzene system (L=benzo-15-crown-5; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as log K_ex(2Na⁺,SrL)=1.0±0.1. Further, the stability constant of the benzo-15-crown-5-sodium complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log b_nb(NaL⁺)=7.8±0.1.     

Extraction of lithium with nitrobenzene solution of strontium bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium 2Li⁺(aq)+SrL₂ ²⁺(nb) 2LiL⁺(nb)+Sr²⁺(aq) taking place in the two-phase water-nitrobenzene system (L=15-crown-5; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as logK _ex (2Li⁺;SrL₂ ²⁺)=−3.7. Further, the stability constant of the 15-crown-5—lithium complex in nitrobenzene saturated with water was calculated: log β_nh(LiL⁺)=7.0.     

Development of multiple prompt gamma-ray analysis

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇔ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system [M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L = p-tert-butylcalix[4]arene-tetrakis (N, N-dimethylthioacetamide); aq = aqueous phase, nb = nitrobenzene phase] were evaluated. Furthermore, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Cs⁺<Rb⁺<K⁺<Li⁺<Na⁺.     

Contribution to the thermodynamics of complexes of alkali metal cations with hexaethyl p-tert-butylcalix[6]arene hexaacetate in the water—nitrobenzene extraction system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+CsL⁺(nb)⇔ML⁺(nb)+Cs⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺ = Li⁺, Na⁺, K⁺, Rb⁺; L = hexaethyl p-tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were determined. Moreover, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Rb⁺<Cs⁺<K⁺<Na⁺<Li⁺.     

Extraction of sodium picrate into nitrobenzene in the presence of dicyclohexyl-18-crown-6

From extraction experiments and -activity measurements, the extraction constant corresponding to the equilibrium Na⁺(aq)+A^–(aq)+L(nb)NaL⁺(nb)+A^–(nb) taking place in the two-phase water-nitrobenzene system (A^–=picrate, L= dicyclohexyl-18-crown-6; aq-aqueous phase, nb=nitrobenzene phase) was evaluated as logK _ex(NaL⁺, A^–)=2.6.Further, the stability constant of the dicyclohexyl-18-crown-6-sodium complex in nitrobenzene saturated with water was calculated: _nb(NaL⁺)=7.8.     

Contribution to the thermodynamics of complexes of alkali metal cations with 18-crown-6 in the water—nitrobenzene extraction system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇄ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L=18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. The stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they are found to increase in the cation order Cs⁺Li⁺Na⁺Rb⁺K⁺. Further, the individual extraction constants for the NaL⁺, KL⁺, RbL⁺ and CsL⁺ complex species in the wate-nitrobenzene system were determined; their values increase in the series Na⁺Rb⁺Cs⁺K⁺.     

Stability of the valinomycin-rubidium complex in water saturated nitrobenzene

From the extraction experiments and -activity measurements, the extraction constant corresponding to the Rb⁺(aq)+CsL⁺(nb)RbL⁺(nb)+Cs⁺(aq) equilibrium in the two-phase water-nitrobenzene system (L=valinomycin; aq=aqueous phase, nb=nitrobenzene phase) was evaluated in the form logK _ex (Rb⁺, CsL⁺)=0.9. Further, the stability constant of the valinomycin-rubidium complex in nitrobenzene saturated with water was calculated as log _nb(RbL⁺)=11.7.     

Extraction of H+, NH4 +, Ag+ and Tl+ into nitrobenzene by using sodium dicarbollylcobaltate in the presence of tetramethyl p-tert-butylcalix[4]arene tetraketone

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇔ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system (M⁺ = H⁺, NH₄⁺, Ag⁺, Tl⁺; L = tetramethyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Tl⁺<NH₄⁺<Ag⁺ <H⁺ <Na⁺.     

Stability of the 15-crown-5-sodium complex in water saturated nitrobenzene

From extraction experiments with²²Na as a tracer, the extraction constant corresponding to the equilibrium Ba²⁺(aq)+2NaL⁺(nb)⇄ ⇄BaL₂ ²⁺(nb)+2Na⁺(aq) taking place in the two-phase water-nitrobenzene system (L=15-crown-5; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as logK _ex (Ba²⁺,2NaL⁺)=3.3±0.1. Further, the stability constant of the complex BaL₂ ²⁺ in nitrobenzene saturated with water was calculated: log β_nh(BaL ₂ ²⁺ )=16.4±0.1.     

Solvent extraction of barium picrate by p-tert-butylcalix[4]arene-tetrakis (N,N-diethylacetamide)

Summary From extraction experiments andg-activity measurements, the extraction constant of the Ba²⁺(aq)+2A^-(aq)+L(nb)?BaL²⁺(nb)+2A^-(nb) equilibrium in the two-phase water-nitrobenzene system (L = p-tert-butylcalix[4]arene-tetrakis (N,N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as logK_ex(BaL²⁺,2A^-)=6.5±0.1. Furthermore, the stability constant of the p-tert-butylcalix[4]arene-tetrakis (N,N-diethylacetamide)̵barium complex in nitrobenzene saturated with water was calculated for at 25 °C as logb_nb(BaL²⁺)=15.4±0.1.     

Kinetics of electrode reaction coupled to ion transfer across the liquid/liquid interface

In the theoretical model it is assumed that a graphite disk electrode is covered by a thin film of solution of decamethylferrocene (dmfc) and some electrolyte CX in nitrobenzene and immersed in an aqueous solution of the electrolyte MX. Oxidation of dmfc is accompanied by the transfer of anion X ⁻ from water into nitrobenzene since it is also assumed that cations dmfc ⁺ and C ⁺ are insoluble in water and cation M ⁺ is insoluble in nitrobenzene. Kinetic parameters of the electrode reaction can be determined if the total potential difference across the nitrobenzene/water interface is maintained constant by adding the electrolytes CX and MX in concentrations which are much higher than the initial concentration of dmfc in nitrobenzene.     

Extraction of lead from water into nitrobenzene by using strontium dicarbollylcobaltate in the presence of benzo-15-crown-5

Summary From extraction experiments andg-activity measurements, the extraction constant corresponding to the equilibrium Pb²⁺(aq)+SrL(nb)?PbL(nb)+Sr²⁺(aq)taking place in the two-phase water-nitrobenzene system (L = benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated aslog K_ex(Pb²⁺,SrL)=0.1±0.1. Further, the stability constant of the benzo-15-crown-5-lead complex in nitrobenzene saturated with water was calculated for a temperature of25 °C:log b_nb(PbL)=13.2±0.1.     

Solvent extraction of magnesium, zinc and manganese into nitrobenzene by using strontium dicarbollylcobaltate in the presence of valinomycin

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq)+SrL²⁺(nb)⇔ML²⁺(nb)+Sr²⁺(aq) taking place in the two-phase water-nitrobenzene system (M²⁺ = Mg²⁺, Zn²⁺, Mn²⁺; L = valinomycin; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the ML²⁺ complexes in water saturated nitrobenzene were calculated. They were found to increase in the order of Mg²⁺<Mn²⁺<Zn²⁺.