Ioanna E. Molinou

Solvation of copper(II) sulfate in binary water/N,N-dimethylformamide mixtures: from the solution to the gas phase.

The solvation of copper(II) sulfate in binary mixtures of water and N,N-dimethylformamide (DMF) is studied by a combined approach using electrochemical studies in solution and a mass spectrometric assay of the solvated ions formed from these solutions upon electrospray ionization (ESI). In the condensed phase, the limiting transference numbers (t(+/-)(o)) and the apparent ion association constants (K(A)s) of CuSO(4) have been determined in water/DMF solutions at 20 degrees C. The t(+)(o) values decrease with increasing DMF content, demonstrating a gradual solvation of Cu(2+) by DMF molecules. The association constants indicate that aggregation becomes more pronounced as the DMF content increases. In order to achieve complementary insight, the intrinsic interactions among the ions and solvent molecules are investigated in gas-phase experiments of the CuSO(4)/water/DMF system using ESI mass spectrometry. Under the conditions used, the dications [Cu(DMF)(n)](2+) (n = 3-6), [Cu(2)(DMF)(n)SO(4)](2+) (n = 2-7), and [Cu(3)(DMF)(n)(SO(4))(2)](2+) (n = 2-7), and the monocations [Cu(OH)(DMF)(n)](+), [Cu(DMF)(n)(HSO(4))](+) (both, n = 1-3), and [Cu(DMF)(n)](+) (n = 1, 2), are formed as the leading copper-containing cations. Likewise, polynuclear copper clusters observed in the anion ESI spectra support partial aggregation occurring in solution. The gas-phase studies clearly support the conclusions that (i) DMF is a highly preferred ligand for CuII in comparison to water and that (ii) DMF supports ion association for which the mass spectrometric data suggest the formation of polynuclear copper clusters.

Transference numbers, conductance and viscosity studies of copper sulfate in ethylene glycol-water mixtures at 20 °C

Cell voltage (emf), conductivities and viscosities of copper(II) sulfate solutions in ethylene glycol–water mixtures have been measured at 20 °C. The transference numbers of CuSO4 have been calculated from emf measurements of concentration cells with transference. The limiting molar (Λ°) and ionic conductances (λ°+,λ°−) as well as the ion association constants (KA) of the salt have been evaluated. The viscosity data have been analysed according to the modified Jones–Dole equation. The Stokes’ radii (rSt) have been evaluated as well. Die EMK, Leitfähigkeiten und Viskositäten von CuSO4 in Äthylenglykol Wässrige Lösungen wurden bei 20 °C gemessen. Die Überführungszahlen von CuSO4 wurden anhand von EMK-Messungen von Zellen ohne Überführung bestimmt. Die Grenzwerte der jeweiligen molaren Leitfähigkeiten (Λ°) sowie die Assoziationskonstanten (KA) des Salzes wurden in allen Lösungsmischungen berechnet. Anhand der molaren Leitfähigkeiten und der Überführungszahlen lässt sich die Ionenleitfähigkeiten (λ°+,λ°−) berechnet. Die Viskositätsmessungen wurden nach der Jones–Dole Gleichung analysiert. Die Stokesschen Radii sind ebenfalls evaluiert worden.

Conductivities, Partial Molar Volumes, and Isentropic Compressibilities of Sodium, Potassium and Ammonium Thiocyanates in Water +N,N-Dimethylformamide Mixtures at 20°C

Abstract Conductance, ultrasonic velocity, and density measurements are reported for NaSCN, KSCN and NH4SCN in water, N,N-dimethylformamide (DMF), and water + DMF mixtures at 20°C. The limiting molar conductances and association constants have been derived from the Lee–Wheaton conductivity equation. The single-ion conductances have been evaluated using Bu4NBPh4 as the “reference electrolyte”. The limiting molar volumes and apparent isentropic compressibilities have been calculated. The ion–ion and ion–solvent interactions have been discussed.

An investigation on ion association and ion solvation of potassium acetate in alcohol solutions

The molar conductivities (Λ) of potassium acetate in methanol (MeOH), ethanol (EtOH), 1-propanol (PrOH), 2-propanol (isoPrOH), 2-methyl-1-propanol (MPrOH), 1-butanol (BuOH), 1-pentanol (PeOH), and benzyl alcohol (BeOH) were measured at 293.15 K. The concentration dependence of Λ was analysed by means of the Lee–Wheaton conductivity equation in the form proposed by Pethybridge and Taba. From the analysis of the experimental Λ values, the limiting molar conductivities (Λo) and the association equilibrium constants (κ α) were determined. The centre-to-centre distance (a) of the formed ion pairs were assumed to be equal to the Bjerrums distance of closest approach. Furthermore, the ultrasonic velocities (u) and the densities (ρ) were measured in order to determine the limiting partial molar volume (V ϕ o) and the limiting apparent isentropic compressibility ( ). The results provide information regarding the association and solvation of the ions of the investigated electrolyte.

Viscosity coefficients of NaSCN, KSCN, NH4SCN and MnSO4, CoSO4, NiSO4, CdSO4 in aqueous binary mixtures of N, N-dimethylformamide at 20 °C

Abstract Viscosities of sodium, potassium, ammonium thiocyanates and manganese, cobalt, nickel, cadmium sulfates have been measured in water + N,N-dimethylformamide (DMF) mixtures at 20 °C. The experimental data have been analyzed using the Jones–Dole equation and the B coefficients have been calculated. The results have been discussed in terms of ion-solvent and solvent-solvent interactions.

Solution properties of polystyrene in mixtures of toluene with ethyl acetate

Abstract The ternary system polystyrene/toluene/ethyl acetate has been studied by viscometry and light scattering. The intrinsic viscosity of the ternary system has been found to undergo a discontinuity over a narrow solvent mixture composition range. This phenomenon is accounted for by assuming conformational changes of the chain.

Thermodynamic investigation of the surface tension of liquid mixtures of cis-decaline with either methyl–acetate or n-pentyl–acetate in the temperature range from 283.15 to 303.15 K

Surface tensions (σ) and densities (ρ) of binary liquid mixtures of cis-decaline with either methyl–acetate (MAC) or n-pentyl–acetate (PAC) were measured over the entire composition range at the temperatures 283.15, 288.15, 298.15 and 303.15 K. The excess surface tensions (σE ) and the excess molar volumes (VE ) were calculated. The σE and VE values were fitted by the Redlich–Kister polynomial equation and the Ak coeffients as well as the standard deviations (d) between the calculated and the experimental excess parameters were derived. The σ values were further used for the calculation of the surface entropy (SS ) and the surface enthalpy (HS ) per unit surface area. The lyophobicity (β) and the surface mole fraction ( ) of the surfactant component (either MAC or PAC) were also derived using the extended Langmuir model. The results were used for the characterisation of the molecular interactions at the surface and the bulk-phase region.