Complexation study of dibenzo-18-crown-6 with UO2 2+ cation in binary mixed non-aqueous solutions

The complexation reaction of macrocyclic ligand, dibenzo-18-crown-6 (DB18C6) with UO₂ ²⁺ cation was studied in ethylacetate-1,2-dichloroethane (EtOAc/DCE), acetonitrile-1,2-dichloroethane (AN/DCE), methanol-1,2-dichloroethane (MeOH/DCE) and ethanol-1,2-dichloroethane (EtOH/DCE) binary solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complex formed between DB18C6 and UO₂ ²⁺ cation is affected by the nature of the solvent systems. A non-linear behaviour was observed for changes of log K _f of (DB18C6.UO₂)⁺² complex versus the composition of the binary mixed solvents. The values of thermodynamic quantities (?S°_c, ?H°_c) for formation of (DB18C6.UO₂)⁺² complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex is enthalpy stabilized and in all cases entropy stabilized and both parameters are affected by the nature and composition of the mixed solvents. In addition, the complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and UO₂ ²⁺ cation was studied in pure AN and the results were compared with those of the (DB18C6.UO₂)⁺² complex.     

Solvent extraction of calcium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexano-18-crown-6 and dicyclohexano-24-crown-8

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-18-crown-6 (DCH18C6, L) and dicyclohexano-24-crown-8 (DCH24C8, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, $ {\text{HL}}_{2}^{ + },$ CaL²⁺ and $ {\text{CaL}}_{2}^{2 + } $ (L = DCH18C6, DCH24C8) are present in the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined. It was found that the stability constants of CaL²⁺ (L = DCH18C6, DCH24C8) for both ligands under study are practically the same in nitrobenzene saturated with water, whereas in this medium the stability of the complex $ {\text{CaL}}_{2}^{2 + } $ involving the DCH24C8 ligand is somewhat higher than that of $ {\text{CaL}}_{2}^{2 + } $ with the ligand DCH18C6.     

A thermodynamic study of complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and La3+, UO 22+ , Ag+, and NH 4+ cations in acetonitrile-tetrahydrofuran binary media using conductometric method

The complex formation between La³⁺, UO₂²⁺ Ag⁺, and NH₄⁺ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the conductometric method. The results show that with the exception of complexation of the NH₄⁺ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log K _f of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]³⁺ > [(DCH18C6)UO₂]²⁺ > [(DCH18C6)Ag]⁺ ∼ [(DCH18C6)NH₄]⁺, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]⁺ > [(DCH18C6)NH₄]⁺ ∼ [DCH18C6)UO₂]²⁺ > [(DCH18C6)Ag]⁺. The text was submitted by the authors in English.     

Determination of the thermodynamic parameters,stoichiometry, and stability constants for complex formation of dicyclohexyl-18-crown-6 and 15-crown-5 with Y3+, La3+, and Hg2+ cations in binary solutions

The complexation of Y³⁺, La³⁺, and nd Hg²⁺ cations with macrocyclic ligands, dicyclohexyl-18-crown-6 (DCH18C6) and 15-crown-5 (15C5) have been studied in acetonitrile (AN)-N,N-dimethylformamide (DMF) binary solutions at different temperatures using conductometric method. The conductance data revealed 1: 1 [ML] stoichiometry for most complexes in pure DMF and AN-DMF binary solutions, except for the (DCH18C6-Y³⁺) complex in pure AN (1: 2, [ML₂]). The stability constants of DCH18C6-La³⁺ and 15C5-La³⁺ in pure AN were higher than in pure DMF at all temperatures. Nonlinear behavior was observed for the stability constants of complexes against the composition of AN-DMF binary solutions at all temperatures. The minimum log K _f value for the 15C5-La³⁺ complex in AN-DMF binary solutions was obtained at χ_AN = 0.5, which may be due to negative excess viscosities η^E of AN-DMF mixtures over the whole composition range with a minimum value of χ_AN = 0.5. Moreover, the selectivity order of DCH18C6 and 15C5 for Y³⁺, La³⁺, and Hg²⁺ cations 25°C depended on the AN-DMF ratio. The thermodynamic parameters (ΔH _C ⁰ ) for complex formation were obtained from the temperature dependences of the stability constants of the complexes using the van’t Hoff plots, and the standard entropy (ΔS _C ⁰ ) was calculated from the relationship: ΔG _{C, 298.15} ⁰ = ΔH _C ⁰ ? 298.15ΔS _C ⁰ .     

A thermodynamic study of complexation of 18-crown-6 with Zn2+, Tl+, Hg2+ and {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} cations in acetonitrile-dimethylformamide binary media and study the effect of anion on the stability constant of (18C6-Na+) complex in methanol solutions

The equilibrium constants and thermodynamic parameters for complex formation of 18-crown-6(18C6) with Zn²⁺, Tl⁺, Hg²⁺ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations have been determined by conductivity measurements in acetonitrile(AN)-dimethylformamide(DMF) binary solutions. 18-crown-6 forms 1:1 complexes [M:L] with Zn²⁺, Hg²⁺ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations, but in the case of Tl⁺ cation, a 1:2 [M:L₂] complex is formed in most binary solutions. The thermodynamic parameters ( $ \Delta {\text{H}}^{ \circ }_{{\text{c}}} $ and $ \Delta {\text{S}}^{ \circ }_{{\text{c}}} $ ) which were obtained from temperature dependence of the equilibrium constants show that in most cases, the complexes are enthalpy destabilized but entropy stabilized and a non-monotonic behaviour is observed for variations of standard enthalpy and entropy changes versus the composition of AN/DMF binary mixed solvents. The obtained results show that the order of selectivity of 18C6 ligand for these cations changes with the composition of the mixed solvent. A non-linear relationship was observed between the stability constants (logK_f) of these complexes with the composition of AN/DMF binary solutions. The influence of the $ {\text{ClO}}^{ - }_{{\text{4}}} $ , $ {\text{NO}}^{ - }_{{\text{3}}} $ and $ {\text{Cl}}^{ - } $ anions on the stability constant of (18C6-Na⁺) complex in methanol (MeOH) solutions was also studied by potentiometry method. The results show that the stability of (18C6-Na⁺) complex in the presence of the anions increases in order: $ {\text{ClO}}^{ - }_{{\text{4}}} $  >  $ {\text{NO}}^{ - }_{{\text{3}}} $  >  $ {\text{Cl}}^{ - } $ .     

Solvent extraction of microamounts of strontium and barium into nitrobenzene by using synergistic mixture of hydrogen dicarbollylcobaltate and dicyclohexano-18-crown-6

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-18-crown-6 (DCH18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, $ {\text{HL}}_{ 2}^{ + } $ , ML²⁺ and $ {\text{ML}}_{ 2}^{ 2+ } $ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that in the mentioned medium the stability constants of the complexes BaL²⁺ and $ {\text{BaL}}_{2}^{2 + }, $ where L = DCH18C6, are somewhat higher than those of the species SrL²⁺ and $ {\text{SrL}}_{2}^{2 + } $ with the same ligand L.     

Thermodynamics of ZrO2+ cation complexation with dibenzo-18-crown-6 in mixed non-aqueous solvents

The complexation reaction of dibenzo-18-crown-6 (DB18C6) with ZrO²⁺ cation was studied in some binary solvent solutions of acetonitrile (AN), 1,2 dichloroethane (DCE), nitromethane (NM) and ethylacetate (EtOAc) with methanol (MeOH), at different temperatures by conductometry method. The stability constant of the resulting 1:1 complex at each temperature was determined using a computer fitting conductance-mole ratio data. The results revealed that, the (DB18C6·ZrO)²⁺ complex is more stable in the EtOAc–MeOH binary mixed solvents compared with the other binary mixed solvent solutions. A non-linear relationship was observed for changes of log?K_f of (DB18C6·ZrO)²⁺ complex versus the composition of the binary mixed solvents. The corresponding standard thermodynamic parameters (ΔH _c ^° , ΔS _c ^° ) were obtained from temperature dependence of the stability constant. The results show that the (DB18C6·ZrO)²⁺ complex is enthalpy destabilized but entropy stabilized and the values along with the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Characteristics of an oxa-diamide–HNO3 extractant in the supercritical fluid extraction of uranium

An extractant is required in the recovery process to drive the uranium to a stage that enables it to be extracted using the extraction solvent. This paper proposes the composition of a composite extractant, N,N,N′,N′-tetrabutyl-3-oxapentane-diamide–HNO₃ (TBODA–HNO₃) as an extractant, to successfully achieve the objective using supercritical carbon dioxide (sc-CO₂). The composite TBODA–HNO₃ extractant has a chemical composition of TBODA(HNO₃)_1.0(H₂O)_1.5. The U(IV) in the UO₂ containing solid phase is directly oxidized to U(VI) in the form of $ {\rm UO}_{2}^{2 + } $ in sc-CO₂, which contains a CO₂-soluble TBODA–HNO₃ extractant at 200 atm and 50 °C. The resulting $ {\rm UO}_{2}^{2 + } $ /TBODA complex can be consequently extracted using acetone-modified sc-CO₂. The chemical composition of the $ {\rm UO}_{2}^{2 + } $ /TBODA complex, which can be extracted by nonpolar sc-CO₂, is proposed in the form of an ion pair: [UO₂(TBODA)₂]²⁺–2( $ {\rm NO}_{3}^{ - } $ ).     

Thermodynamic behavior of complexation process between benzo-15-crown-5 with Li+, Na+, K+, and NH4 + cations in acetonitrile–methanol binary media

The stability constants of 1:1 (M:L) complexes of benzo-15-crown-5 (B15C5) with Li⁺, Na⁺, K⁺ and NH₄ ⁺ cations, the Gibbs standard free energies ( $ \Updelta {\text{G}}_{\text{c}}^{ \circ } $ ), the standard enthalpy changes ( $ \Updelta {\text{H}}_{\text{c}}^{ \circ } $ ) and standard entropy changes ( $ \Updelta {\text{S}}_{\text{c}}^{ \circ } $ ) for formation of these complexes in acetonitrile–methanol (AN–MeOH) binary mixtures have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and the studied cations is 1:1 (M:L). In most cases, addition of B15C5 to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The results show that the selectivity order of B15C5 for the metal cations changes with the nature and composition of the binary mixed solvent. The values of standard enthalpy changes ( $ \Updelta {\text{H}}_{\text{c}}^{ \circ } $ ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy ( $ \Updelta {\text{S}}_{\text{c}}^{ \circ } $ ) were calculated from the relationship $ \Updelta {\text{G}}_{{{\text{c}},298.15}}^{ \circ } = \Updelta {\text{H}}_{\text{c}}^{ \circ } - 298.15\Updelta {\text{S}}_{\text{c}}^{ \circ } $ . A non-linear behavior was observed between the stability constants (log K_f) of the complexes and the composition of the acetonitrile–methanol (AN–MeOH) binary solution. The results obtained in this study, show that in most cases, the complexes formed between B15C5 and Li⁺, Na⁺, K⁺ and NH₄ ⁺ cations are both enthalpy and entropy stabilized and the values of these thermodynamic quantities change with the composition of the binary solution.     

Study of complexation process between N-phenylaza-15-crown-5 with yttrium cation in binary mixed solvents

The complexation reaction between Y³⁺ cation with N-phenylaza-15-crown-5(Ph-N15C5) was studied at different temperatures in acetonitrile–methanol (AN/MeOH), acetonitrile–propanol (AN/PrOH), acetonitrile–1,2 dichloroethane (AN/DCE) and acetonitrile–water (AN/H₂O) binary mixtures using the conductometric method. The results show that in all cases, the stoichiometry of the complex is 1:1 (ML). The values of formation constant of the complex which were determined using conductometric data, show that the stability of (Ph-N15C5.Y)³⁺ complex in pure solvents at 25?°C changes in the following order: PrOH?>?AN?>?MeOH and in the case of binary mixed solutions at 25?°C it follows the order: AN–DCE?>?AN–PrOH?>?AN–MeOH?>?AN–H₂O. The values of standard thermodynamic quantities (?H _c ^° and ?S _c ^° ) for formation of (Ph-N15C5.Y)³⁺ complex were obtained from temperature dependence of the formation constant using the van’t Hoff plots. The results show that in most cases, the complex is entropy and enthalpy stabilized and these parameters are influenced by the nature and composition of the mixed solvents. In most cases, a non-linear behavior was observed for variation of log K_f of the complex versus the composition of the binary mixed solvents. In all cases, an enthalpy–entropy compensation effect was observed for formation of (Ph-N15C5.Y)³⁺ complex in the binary mixed solvents.     

Study of Complex Formation Between Dicyclohexano-18-Crown-6 (DCH18C6) with Mg 2+, Ca2+, Sr 2+, and Ba2+ Cations in Methanol–Water Binary Mixtures Using Conductometric Method

The complexation reactions between Mg²⁺,Ca²⁺,Sr²⁺ and Ba²⁺ metal cations with macrocyclic ligand, dicyclohexano-18-crown-6 (DCH18C6) were studied in methanol (MeOH)–water (H₂O) binary mixtures at different temperatures using conductometric method . In all cases, DCH18C6 forms 1:1 complexes with these metal cations. The values of stability constants of complexes which were obtained from conductometric data show that the stability of complexes is affected by the nature and composition of the mixed solvents. While the variation of stability constants of DCH18C6-Sr ²⁺ and DCH18C6-Ba²⁺versus the composition of MeOH–H₂O mixed solvents is monotonic, an anomalous behavior was observed for variations of stability constants of DCH18C6-Mg²⁺ and DCH18C6-Ca²⁺ versus the composition of the mixed solvents. The values of thermodynamic parameters (ΔH_c°, ΔS_c°) for complexation reactions were obtained from temperature dependence of formation constants of complexes using the van’t Hoff plots. The results show that in most cases, the complexation reactions are enthalpy stabilized but entropy destabilized and the values of thermodynamic parameters are influenced by the nature and composition of the mixed solvents. The obtained results show that the order of selectivity of DCH18C6 ligand for metal cations in different concentrations of methanol in MeOH–H₂O binary system is: Ba²⁺>Sr²⁺>Ca²⁺> Mg²⁺.     

A combined experimental and density functional theory study on the complexation ability of 15-crown-5 with Li+, Na+, K+, and NH4 + cations

The complexation processes among Li⁺, Na⁺, K⁺, and NH₄ ⁺ cations with the macrocyclic ligand, 15-crown-5 (15C5) have been studied in acetonitrile–methanol binary mixtures at different temperatures using conductometric method. The stability constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data at various temperatures. The values of thermodynamic parameters ( $ \Updelta H_{\text{c}}^{^\circ } $ and $ \Updelta S_{\text{c}}^{^\circ } $ ) for the formation of the complexes were obtained from temperature dependence of the stability constants of complexes using van’t Hoff plots. In addition, a theoretical study has been carried out using density functional theory to obtain the stability of the complexes and the geometrical structure of the 15C5 and its complexes with Li⁺, Na⁺, K⁺ and NH₄ ⁺ cations in the gas phase. We compared the experimental data with those obtained by quantum chemistry calculations to investigate the effect of the solvent on complexation process.     

Effect of pH, fulvic acid and temperature on the sorption of uranyl on ZrP2O7

The sorption of UO ₂ ²⁺ onto ZrP₂O₇ was studied using the batch technique and the point of zero charge of ZrP₂O₇ was obtained through mass titration. The results indicated that sorption of UO ₂ ²⁺ onto ZrP₂O₇ was strongly affected by pH, solid-to-liquid ratio (m/V), the species of electrolyte in solution and fulvic acid (FA), but was insensitive to ionic strength. The sorption of UO ₂ ²⁺ increased with increasing pH and m/V. The presence of FA enhanced UO ₂ ²⁺ sorption onto ZrP₂O₇ at low pH. The presence of phosphate or sulfate caused opposite effects on the sorption of UO ₂ ²⁺ onto ZrP₂O₇. Addition of citrate also significantly affected UO ₂ ²⁺ sorption. The sorption of UO ₂ ²⁺ increased as the temperature of the system increased. The Langmuir and Freundlich models were used to simulate the sorption isotherms of UO ₂ ²⁺ onto ZrP₂O₇ at different temperatures. The results indicated that the Freundlich model described UO ₂ ²⁺ sorption better than the Langmuir model. Thermodynamic parameters for the sorption process were calculated from the temperature dependent sorption isotherms. The results suggested that the sorption process of UO ₂ ²⁺ onto ZrP₂O₇ is spontaneous and endothermic. The desorption process of UO ₂ ²⁺ from ZrP₂O₇ was also investigated and it was found that sorption onto ZrP₂O₇ was irreversible.     

Study of complex formation between 18-crown-6 and diaza-18-crown-6 with uranyl cation (UO2 2+) in some binary mixed aqueous and non-aqueous solvents

The complexation reaction between UO₂ ²⁺ cation with macrocyclic ligand, 18-crown-6 (18C6), was studied in acetonitrile–methanol (AN–MeOH), nitromethane–methanol (NM–MeOH) and propylencarbonate–ethanol (PC–EtOH) binary mixed systems at 25 °C. In addition, the complexation process between UO₂ ²⁺ cation with diaza-18-crown-6 (DA18C6) was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–ethanol (AN–EtOH), acetonitrile–ethylacetate (AN–EtOAc), methanol–water (MeOH–H₂O), ethanol–water (EtOH–H₂O), acetonitrile–water (AN–H₂O), dimethylformamide–methanol (DMF–MeOH), dimethylformamide–ethanol (DMF–EtOH), and dimethylformamide–ethylacetate (DMF–EtOAc) binary solutions at 25 °C using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between (18C6) and (DA18C6) with UO₂ ²⁺ cation in most cases is 1:1 [M:L], but in some solvent 1:2 [M:L₂] complex is formed in solutions. The values of stability constants (log K_f) of (18C6 · UO₂ ²⁺) and (DA18C6 · UO₂ ²⁺) complexes which were obtained from conductometric data, show that the nature and also the composition of the solvent systems are important factors that are effective on the stability and even the stoichiometry of the complexes formed in solutions. In all cases, a non-linear relationship is observed for the changes of stability constants (log K_f) of the (18C6 · UO₂ ²⁺) and (DA18C6 · UO₂ ²⁺) complexes versus the composition of the binary mixed solvents. The stability order of (18C6 · UO₂ ²⁺) complex in pure studied solvents was found to be: EtOH > AN ≈ NM > PC ≈ MeOH, but in the case of (DA18C6 · UO₂ ²⁺) complex it was : H₂O > MeOH > EtOH.     

Exploring antibiotic resistance based on enzyme hydrolysis by microcalorimetry

In an effort to understand the reactions of antibiotics hydrolysis with metallo-β-lactamases (MβLs), the thermokinetic parameters of cefazolin hydrolysis with B1 subclass MβL CcrA from Bacteroides fragilis were determined by microcalorimetric method. The values of activation free energy $ \Updelta G_{ \ne }^{\theta } $ are 88.032 ± 0.038, 89.075 ± 0.025, 90.095 ± 0.034, and 91.261 ± 0.044 kJ mol^?1 at 293.15, 298.15, 303.15, and 308.15 K, respectively, the activation enthalpy $ \Updelta H_{ \ne }^{\theta } $ is 25.278 ± 0.005 kJ mol^?1, the activation entropy $ \Updelta S_{ \ne }^{\theta } $ is ?213.99 ± 0.14 J mol^?1 K^?1, the apparent activation energy E is 27.776 kJ mol^?1, and the reaction order is 1.4. The results indicated that the cefazolin hydrolysis with CcrA is an exothermic and spontaneous reaction. An association between the thermokinetic and kinetic parameters was revealed, which is that the catalytic constant K _cat increase with increase in $ \Updelta H_{ \ne }^{\theta } $ .     

The phase diagrams of the systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 323.15 K and Pitzer model

The solubilities and the relevant physicochemical properties of the systems MgCl₂ + MgB₆O₁₀ + H₂O and MgSO₄ + MgB₆O₁₀ + H₂O at 323.15 K were determined by the method of isothermal dissolution, and the phase diagrams and the diagrams of physicochemical properties versus composition were plotted. Both of the systems belong to a simple eutectic type, and neither double salts nor solid solution were found. Based on the extended Harvie-Weare (HW) model and its temperature-dependent equations, the value of the singlesalt Pitzer parameters ??⁽⁰⁾, ??⁽¹⁾, ??⁽²⁾, and C ^? for MgCl₂, MgSO₄, and Mg(B₆O₇)(OH)₆, the mixed ion-interaction parameters $\theta _{Cl, B_6 O_{10} }$ , $\theta _{SO_4 , B_6 O_{10} }$ , $\Psi _{Mg, Cl, B_6 O_{10} }$ , $\Psi _{Mg, SO_4 , B_6 O_{10} }$ , the average equilibrium constants (lnK _aver) of solids in the systems and the Debye-Hückel parameter A ^? were fitted. Using the Pitzer parameters and the average equilibrium constants of solids at equilibrium, the solubilities of the two systems at 323.15 K have been calculated. Comparisons between the calculated and experimental results show that the predicted solubilities agree well with experimental data.     

Thermodynamic study of metal corrosion and inhibitor adsorption processes in copper/N-1-naphthylethylenediamine dihydrochloride monomethanolate/nitric acid system: part 2

N-1-Naphthylethylenediamine dihydrochloride monomethanolate (N-NEDHME) was tested as a corrosion inhibitor for copper in 2 M HNO₃ solution using the standard gravimetric technique at 303–343 K. N-NEDHME acts as an inhibitor for copper in an acidic medium. Inhibition efficiency increases with increase in concentration of N-NEDHME but decreases with a rise in temperature. Thermodynamic parameters such as adsorption heat ( $ \Updelta H_{\text{ads}}^\circ $ ), adsorption entropy ( $ \Updelta S_{\text{ads}}^\circ $ ) and adsorption free energy ( $ \Updelta G_{\text{ads}}^\circ $ ) were obtained from experimental data of the temperature studies of the inhibition process at five temperatures ranging from 303 to 343 K. Kinetic parameters activation such as $ E_{a} $ , $ \Updelta H_{\text{a}}^\circ $ , $ \Updelta S_{\text{a}}^\circ $ and pre-exponential factors have been calculated and are discussed. Adsorption of N-NEDHME on the copper surface in 2 M HNO₃ follows the Langmuir isotherm model.     

Solvent extraction of strontium and barium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexano-24-crown-8

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-24-crown-8 (DCH24C8, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, $ {\text{HL}}_{2}^{ + }, $ ML²⁺ and $ {\text{ML}}_{ 2}^{2 + } $ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that in water–saturated nitrobenzene, the stability constants of the complexes BaL²⁺ and $ {\text{BaL}}_{ 2}{^{2 + }}, $ where L = DCH24C8, are somewhat higher than those of the corresponding species SrL²⁺ and $ {\text{SrL}}_{ 2}{^{2 + }} $ with the same ligand L.     

Interaction of uranyl ion with few molecules of water: thought (computational) scenarios with hydrogen bonding motif

The interaction of the uranyl ion $\hbox{UO}_{2}^{2+}$ with one, two and three molecules of water is computationally modeled. It is demonstrated that the dihydration potential energy surface of $\hbox{UO}_{2}^{2+}$ is partitioned into two bonding regions which correspondingly determine the weak and strong regime of solvation: if the former describes the traditional filling of the first solvation shell, the latter develops, via the hydrogen bonding interaction, to the metastable complex [UO₂(OH)]⁺-H₃ O⁺ with a rather short lifetime. An addition of water molecule from infinity to its H₃ O⁺ side results in the formation of the Zundel cation and spontaneous dissociation into the latter and [UO₂(OH)]⁺. “…we are perhaps not far removed from the time when we shall be able to submit the bulk of chemical phenomena to calculation.” Joseph Louis Gay-Lussac Memoires de la Sociétè d’Arcueil 2, 207 (1808)¹