engleski

Conductance study of ion-pairing of alkali picrate and tetraphenylborate complexes with some macrocyclic polyethers in methanol

The conductance of dibenzo-18-crown-6 (DB18C6), bis(3, 5-di-tert-butylbenzo)-18-crown6 (dtbDB18C6) and dibenzo-24-crown-8 (DB24C8) with sodium and potassium picrates and tetraphenylborates was investigated in methanol.

conductivity ; ion-pairing ; macrocyclic polyethers

The conductance of dibenzo-18-cmwn-6 (DB18C6), bis (3, 5-di-, tert-butylbenzo)-18-crown-6 (dtbDB18C6) and dibenzo- 24-crown-8 (DB24C8) complexes with sodium and potassium picrates and tetr-a ; phenylborates was investigated in methanol at 25 •c. Shedlovsky plots gave straight lines from which the limiting conductances, .Ao, and ion-pai.r dissociation constants, Kv, were calculated. Generally, tetraphenylbora:te complexes are slightly more dissociated than the corrnsponding picrate complexes, as are also the potassium complexes compared to those of the sodium salts. The results obtained are compared with !those obtaillled for the conductance of sodium and po.tassium picrates and tetraphenylborates in methanol, and are discussed in terms of the polyether interactions with al•kali cation which are controlled by their size, solvent interactions with the polyether- cation complexes, size and charge density of the counterion, and the steric factors caused by the presence of the bulky tert-butyl substituents in the polyether molecule.