Conductimetric Behaviour of Tetraphenylphosphonium Chloride and Sodium Tetraphenylborate in Water-Ethanol Mixtures at 25°C

Viscometric and Conductometric Studies of Solvation Behaviour of Tetraalkylammonium Salts in the Binary Mixtures of Dimethylsulfoxide and Methanol at 298.15 K

Molar conductance and viscosity of some tetraalkylammonium perchlorates (R4NClO4 where R = Methyl, Ethyl, Propyl, Butyl) have been measured in the concentration range (30–500) × 10−4 mol kg−1 at 298.15 K in the binary mixtures of dimethylsulfoxide (DMSO) + methanol (MeOH) containing 0, 20, 40, 50, 60, 80 and 100 mol% methanol. Conductance data has been analyzed using the Shedlovsky equation and the viscosity data by Jones-Dole equation. The limiting ionic conductances ( λ ± o $\lambda_{\pm}^{o}$ ) were used to calculate the solvated radii (ri ) of the ions. The A and B coefficients of the Jones-Dole equation are positive in all salts. The A coefficients are in reasonable good agreement with the limiting theoretical values (Aη ) calculated using Falkenhagen-Vernon equation. The variation of the ionic B± coefficients as well as the actual solvated radii (ri ) with solvent composition in DMSO + MeOH mixtures show the preferential solvation of tetraalkylammonium ions by MeOH and MeOH-rich region of the mixtures. The tetraalkylammonium ions exhibit solvation in the order Me4N+ > Et4N+ > Pr4N+ > Bu4N+.

Solvation of Some Tetraalkylammonium Salts Investigated Conductometrically and Viscometrically in Binary Mixtures of Acetonitrile + Methanol at 298.15 K

Molar conductances and viscosities of some tetraalkylammonium perchlorate salts (R4NClO4 where R=methyl, ethyl, propyl, butyl) have been measured in the concentration range (30–500)×10−4 M in the binary mixtures of acetonitrile (AN)+methanol (MeOH) containing 0, 20, 40, 60, 80 and 100 mol% methanol at 298.15 K. Conductance data was analyzed by the Shedlovsky equation and the viscosity data by Jones–Dole equation. The limiting ionic conductances (λ o ±) were used to calculate the solvated radii (r i ) of the ions. The A and B coefficients of the Jones–Dole equation are positive in all salts. The A coefficients are in reasonably good agreement with the limiting theoretical values (Aη) calculated using Falkenhagen–Vernon equation. The variation of the actual solvated radii (r i ) as well as the ionic B ± coefficients with solvent composition in AN+MeOH mixtures shows the preferential solvation of tetraalkylammonium ions by methanol-rich region of the mixtures. The extent of solvation of the tetraalkylammonium ions is in the order Me4N+>Et4N+>Pr4N+>Bu4N+.

Hydration of Tetraphenylphosphonium and Tetraphenylborate Ions by Dielectric Relaxation Spectroscopy

A systematic study of the dielectric relaxation spectra of aqueous solutions of NaBPh4 and Ph4PCl has been made at solute concentrations of 0.02 < or = c/M < or = 0.82 and 0.20, respectively, and over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) at 25 degrees C. The spectra were best described by a superposition of four Debye processes, consisting of a very small ion-pair contribution with an average relaxation time of about 300 ps, a "slow"-water relaxation at 17 ps, and two bulk-water relaxations at 8 ps and 0.25 ps, respectively. The slow-water process has been assigned to the presence of a sheath of water molecules surrounding BPh4- and Ph4P+, whose structure has been enhanced by its proximity to the bulky hydrophobic phenyl rings. A structure-making effect on the remaining solvent water can also be observed at low concentrations. More importantly, BPh4- and Ph4P+ show almost identical hydration characteristics, which provides indirect support for the use of the tetraphenylphosphonium tetraphenylborate reference electrolyte assumption in deriving single-ion thermodynamic properties.