An electrochemical method for determination of the standard Gibbs energy of anion transfer between water and n-octanol

Gulaboski, Rubin and Mirceski, Valentin and Scholz, Fritz (2002) An electrochemical method for determination of the standard Gibbs energy of anion transfer between water and n-octanol. Electrochemistry Communications, 4 (4). pp. 277-283. ISSN 13882481

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Official URL: http://dx.doi.org/10.1016/S1388-2481(02)00264-3

Abstract

The transfer of the ions Cl�, Br�, I�, ClO� 4 , SCN�, NO� 3 , BF� 4 , and ðC6H5Þ4B� across the waterjn-octanol (WjOC) liquid interface was studied and the standard Gibbs energies of ion transfer were determined. The ion transfer was achieved by oxidation of decamethylferrocene dissolved in a droplet of n-octanol that was attached to a graphite electrode immersed in the aqueous solutions of the respective alkali salts of the anions. The electrode reaction can be described by the equation: dmfcðOCÞ þ X� ðWÞ¢dmfcþ ðOCÞ þ X� ðOCÞ þ e�, where X� is the transferred anion. Square-wave voltammetry at this three-phase arrangement was utilised to determine the formal potential of the decamethylferrocene/decamethylferrocenium ðdmfc=dmfcþÞ couple under the condition of ion transfer across the waterjn-octanol interface. For calibration the standard Gibbs energies of ion transfer have been extrapolated to octanol from the series of known data for methanol, ethanol, n-propanol, and n-butanol. All these data are consistent and the experimental dependence of the formal potentials on the standard Gibbs energies is as predicted by theory. The validity of data is further supported by calculations of Gibbs energies of ion transfer using the Born theory. Until now it was not possible to perform electrochemical measurements at the waterjn-octanol interface because in the conventional four-electrode cells this interface cannot be polarised. With the new method it is now for the first time possible to determine the Gibbs energies of transfer of ions across the waterjn-octanol interface. These values are of very wide use for assessing the lipophilicity of compounds in chemistry, medicine, and pharmacology.

Item Type: Article
Uncontrolled Keywords: ion transfer, octanol, lipophilicity, voltammetry, drug design
Subjects: Medical and Health Sciences > Basic medicine
Natural sciences > Biological sciences
Natural sciences > Chemical sciences
Natural sciences > Physical sciences
Divisions: Faculty of Agriculture
Depositing User: Rubin Gulaboski
Date Deposited: 31 Oct 2012 13:15
Last Modified: 01 Nov 2012 10:07
URI: http://eprints.ugd.edu.mk/id/eprint/163

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