Dielectric studies of some tri-n-alkylammonium nitrates and perchlorates in benzene solutions at 298.15 K

Abstract

The partial molar volumes, partial molar refractions and partial molar polarizations of some tri-n-alkylammonium nitrates and perchlorates in benzene solutions have been determined at 298.15 K in the concentration range up to 0.005 mole fraction of solute and are found to be independent of concentration. The dipole moments of the solutes at infinite dilution have been calculated. On the basis of a model of an ion pair with mutually polarizable ions and a permanent dipole moment on the cation, the interionic distance, total electrostatic interaction energy and energy due to the mutual polarization of the ions in an ion pair have been calculated. The interaction energy due to the mutual polarization of ions in the ion pair is found to be an important part of the total electrostatic interaction energy. In addition, it has been shown that the ion pairs investigated belong to the class of contact ion pairs. A comparison of the parameters determined with those of tri-n-alkylammonium halides shows that the values for tri-n-alkylammonium nitrates are close to those of analogous bromides, while those of tri-n-alkylammonium perchlorates are close to those of iodides. This is in accordance with the nearly equal crystallographic radii of nitrate and bromide ions, as well as of perchlorate and iodide ions.