SINGLE-ION TRANSFER ENERGETICS IN SOME AQUEOUS ALKANOLS AND THE STRUCTUREDNESS OF AQUO-ORGANIC SOLVENTS

Single-ion transfer energetics of some ions based on the widely used t etraphenylarsonium tetraphenylborate (TATB) reference electrolyte assu mption have been determined in aqueous mixtures of 10, 20, 30, 50 & 70 wt% alkanols like ethanol (EtOH) and 2-propanol (2-PrOH) from solubil ity measurements of KPi, Ph(4)AsPi, KPh4B and Ph4AsI [Pi-picrate, Ph=p henyl] at five equidistant temperatures in the range 15-35 degrees C. Transfer free energies, Delta G(1)(0) (i), of the ions in aqueous EtOH and 2-PrOH as well as those in aqueous mixtures of methanol (MeOH) an d t-butanol (t-BuOH), as obtained from the literature, after eliminati on of cavity effect and Born-type and ion-dipole-type electrostatic in teracton effects, helped reveal acid-base type interaction effect of s olvents that dictate transfer chemical free energies of the ions, Delt a G(t,ch)(0) (i). On the other hand, transfer entropies, T Delta S-t,c h(0) (i), obtained after due correction of cavity and Born-type electr ostatic effects from T Delta S-t(0) (i) values, when analysed in the l ight of Kundu et al's four-step transfer process as well as the fact t hat increasing hydrophobicity of the cosolvents helps increase the 3D- structuredness of these aquo-alkanolic solvents, led us to conclude th at entropies of single ions rather than the complete electrolytes, ser ve as a better structural probe for aquo-organic solvents. This has al so been substantiated from the corresponding behaviour of some small c ations and anions in aqueous dimethyl sulphoxide (DMSO) and acetonitri le (ACN) solvents.