The Trifluoroacetic Acid Solvent System. Part IV. Triple Ions

Abstract

Electrolytes studied in 100'j/, trifluoroacetic acid exhibit a minimum in equivalent conductivity with increasing solute concentration. This behavior is accounted for by the formation of triple-ions at higher concentrations. Triple-ion dissociation constants, k , have been evaluated and, in general, they show the opposite trend with changing ion size to that of the ion-pair dissociation constants; that is the triple-ions of smaller ions are more dissociated. The experimentally observed trend is accounted for by using a partial ionic charge instead of unit charge for the ion-pair charges in the theoretical Fuoss expression for k .The excellent extrapolation of the triple-ion data to give a value of A°Kd for the ion-pair, which agrees well with that determined from a Fuoss plot, permits an estimate of A0 for LiO,CCF, from the triple-ion data.Les electrolytes etudies dans I'acide trifluoroacetique a 100% montrent un minimum, i conductivite tquivalente, pour une concentration croissante en solute. Ce phtnomine s'explique par la formation d'ions triples en concentrations elevees. Les constantes de dissociation des ions triples k ont ete evaluees; elles varient generalement en sens contraire, par rapport aux constantes de dissociation des paires d'ions, avec le changement dans la taille de l'ion. Cette tendance, observee experimentalement, a ete interpretee en utilisant une charge ionique partielle, au lieu de l'unite pour les charges des paires d'ions dans I'expression thtorique de Fuoss pour k.L'excellente extrapolation des donntes sur I'ion triple pour la valeur A°Kd de la paire d'ion, en bon accord avec la valeur tiree de la courbe de Fuoss, permet une estimation de A0 pour LiO,CCF, a partir des donnees sur I'ion triple.

Aqueous trifluoroacetic acid as a medium for organic reactions. I. Acidity functions and the identity of the manganese(VII) species found in powerfully acidic media

“…Values of '11' for potassium permanganate varied from 3.0 at high concentration (0.05 molal) to 5.2 at low concentration (0.004 molal). Interestingly water appeared to behave like an electrolyte at low concentration (n = 1.8 at 0.012 molal), although conductivity studies have shown that it is not an electrolyte (3,30). Similar anomalous behaviour has been observed for water in nitric acid (31).…”