Rajani Dewan

Ion-pair and triple-ion formation in low permittivity solvent: a conductometric study

Conductivities of some tetraalkylammonium iodides, namely, tetramethylammonium iodide (Me4NI), tetraethylammonium iodide (Et4NI), tetrabutylammonium iodide (Bu4NI), tetrapentylammonium iodide (Pen4NI), tetrahexylammonium iodide (Hex4NI) and tetraheptylammonium iodide (Hep4NI) were measured at 298.15 K aniline. A minimum in the conductometric curves (molar conductance, Λ vs. square root of concentration, √c) was observed at concentrations which depend both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M+ + X− ↔ MX) and triple-ions (2M+ + X− ↔ M2X+; M+ + 2X− ↔  ). A linear relationship between the triple-ion formation constants [log(K T/K P)] and the salt concentrations at the minimum conductivity (log C min) was given for all salts in aniline. The formation of triple-ions might be attributed to the ion sizes in aniline in which Coulombic interactions and covalent bonding forces act as the main forces between the ions (R4N+ ··· X−).