Thermodynamics of Ionic Association of Tetraphenylphosphonium, Tetraphenylarsonium, and Some Common Cations in 2-Methoxyethanol Using Conductometry and FT-Raman Spectroscopy

Abstract

Precise measurements on electrical conductances and Fourier Transform (FT) Raman spectra of solutions of tetraphenylarsonium chloride (Ph4AsCl), tetraphenylphosphonium chloride (Ph4PCl), tetraphenylphosphonium bromide (Ph4PBr), lithium tetrafluoroborate (LiBF4), and sodium tetrafluoroborate (NaBF4) in 2-methoxyethanol (ME) at temperatures 288.15 ≤ T/K ≤ 308.15 are reported. The conductance data were analyzed by the 1978 Fuoss conductance−concentration equation. Thermodynamics of the association processes were also studied, and the Coulombic forces are found to play a major role in the association processes. The Raman spectra suggest the presence of “spectroscopically free” Cl-, Br-, and BF4 - ions in solution, thus substantiating the moderate ion-pair formation constants for these electrolytes obtained from conductometric measurements. The observed processes were interpreted by an Eigen multistep mechanism. Raman spectra also indicate that the cations get attached to the ME molecules through the ethereal oxygen atom rather than through the alcoholic oxygen of the solvent molecules.

The Structure and Thermodynamics of Ion Association and Solvation of Some Thiocyanates and Nitrates in 2-Methoxyethanol Studied by Conductometry and FTIR Spectroscopy

“…Such studies are complemented with structural studies of the metal ion solvates using different spectroscopic methods. Recently, we have initiated a comprehensive program to study the solvation and association behavior of 1:1 electrolytes in different nonaqueous solvents from the measurements of various transport, thermodynamic, and spectroscopic properties. − In this paper, an attempt has been made to reveal the nature of various types of interactions prevailing in solutions of potassium thiocyanate (KCNS), ammonium thiocyanate (NH 4 CNS), sodium nitrate (NaNO 3 ), and ammonium nitrate (NH 4 NO 3 ) in 2-methoxyethanol from precise conductivity and Fourier transform infrared spectral (FTIR) measurements.…”

Thermodynamic Studies on Silver and Thallium Nitrate

“…The obtained equilibrium constants (K A ) for the ion-association reaction served to investigate the thermodynamics of this process. Consequently, the standard Gibbs energy ( G A ), the enthalpy ( H A ), and the entropy ( S A ) of the ion-association process were calculated according to the following equations [21][22][23]: …”

Limiting Diffusion Coefficients for Ions and Nonelectrolytes in Solvents Water, Methanol, Ethanol, Propan-1-ol, Butan-1-ol, Octan-1-ol, Propanone and Acetonitrile at 298 K, Analyzed Using Abraham Descriptors

“…We have not been able to extend our studies to additional solvents simply because of the lack of data on either non-electrolytes or ionic species. Conductance data exists for ions in 2-methoxyethanol [79,80], in N,N-dimethylformamide [66,81] and in formic acid [82], and these could be used to obtain corresponding limiting diffusion coefficients through Eq. 2.…”