Thermodynamics of Ion Association and Solvation in 2-Methoxyethanol: Behavior of Tetraphenylarsonium, Picrate, and Tetraphenylborate Ions from Conductivity and Ultrasonic Data

Precise measurements on electrical conductances and ultrasonic velocities of solutions of potassium picrate (KPic), potassium tetraphenylborate (KBPh 4 ), tetrabutylammonium tetraphenylborate (Bu 4 NBPh 4 ), and tetraphenylarsonium picrate (Ph 4 AsPic) in 2-methoxyethanol (ME) at temperatures 288.15 ≤ T /K ≤ 308.15 have been reported. The conductance data have been analyzed by the 1978 Fuoss conductance−concentration equation. Thermodynamics of the association processes have also been studied and the Coulombic forces are found to play a major role in the association processes. The limiting ionic conductances have been estimated from the appropriate division of the limiting molar conductivity values of the “reference electrolyte” Bu 4 NBPh 4 . Strong association was found for all these salts in this solvent medium. The results strongly suggest the electrostriction of the solvent molecules around the potassium and picrate ions, while for the larger tetrabutylammonium and tetraphenylarsonium ions they are accommodated inside the space between the alkyl or aryl chains attached to the nitrogen or arsenic atom; for tetraphenylborate ion, however, neither electrostriction nor penetration of the solvent molecules is found to be important.