Probing subsistence of ion-pair and triple-ion of an ionic salt in liquid environments by means of conductometric contrivance

Abstract

Qualitative and quantitative analyses of molecular interaction prevailing in ionic salt-organic solvent media, probed by electrical conductances have been reported. Tetrabutylammonium tetrafluoroborate [Bu4NBF4] in acetonitrile (CH3CN), methanol (CH3OH), dimethylsulfoxide (DMSO) and 1,3-dioxolane (1,3-DO) have been studied at 298.15K. The extent of interaction is expressed in terms of the association constant (KA) and shows the interaction to be a function of viscosity. Limiting molar conductances (Λo), association constants (KA), and the association diameter (R) for ion-pair formation have been analyzed using the Fuoss conductance-concentration equation (1978). The observed molar conductivities were explained by the formation of ion-pairs (M++X−↔MX, KP) and triple-ions (2M++X−↔M2X+; M++2X−↔MX2−, KT). The Walden product is obtained and discussed. The deviation of the conductometric curves (Λ vs c1/2) from linearity for the electrolyte in 1,3-dioxolane indicates triple-ion formation, and therefore the corresponding conductance data have been analyzed by using the Fuoss–Kraus theory of triple-ions. The limiting ionic conductances (λo±) have been calculated from the appropriate division of the limiting molar conductivity value of tetrabutylammonium tetraphenylborate [Bu4NBPh4] as the “reference electrolyte” method along with a numerical evaluation of ion-pair and triple-ion formation constants (KP≈KA and KT). The results have been interpreted in terms of solvent properties and configurational theory.