Ion-pair and triple-ion studies of some tetraalkylammonium halides in pure 1,3-dioxolane at 298.15Â K

Conductivities of some tetraalkylammonium halides, viz. tetramethylammonium iodide (Me4NI), tetraethylammonium bromide (Et4NBr), tetraethylammonium iodide (Et4NI), tetra-n-propylammonium bromide (Pr4NBr), tetra-n-butylammonium bromide (Bu4NBr), tetra-n-butylammonium iodide (Bu4NI) and tetra-n-heptylammonium bromide (Hp4NBr) were measured at 298.15 K in 1,3-dioxolane which has a low permittivity (ε = 7.13). A minima in the conductometric curves (molar conductance, Λ vs. square root of concentration, √c) was observed for concentrations which were dependant upon both the salt and the solvent. 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). A linear relationship between the triple-ion formation constants [log (KT/KP)] and the salt concentrations at the minimum conductivity (log Cmin) was given for all the salts in 1,3-dioxolane. The formation of triple-ions might be attributed to the ion sizes in solutions in which Coulombic interactions and non-Coulombic interactions act as the main forces between the ions (R4N+…..X−).