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

TLDR: In this paper, the transfer of the ions Cl −, Br −, I −, ClO 4 −, SCN −, NO 3 −, BF 4 −, and (C 6 H 5 ) 4 B − across the water| n -octanol (W|OC) liquid interface was studied and the standard Gibbs energies of ion transfer were determined.

About: This article is published in Electrochemistry Communications.The article was published on 2002-04-01 and is currently open access. It has received 110 citations till now. The article focuses on the topics: Octanol & Gibbs free energy.

Figures

Fig. 1. SW voltammetric response of an n-octanol droplet containing 0.05 mol dm 3 dmfc attached to a paraffin impregnated graphite electrode, which is immersed in 1 mol dm 3 aqueous solution of KCl (1), KI (2), and KBr (3). The experimental conditions were: SW frequency f¼ 100 Hz, SW amplitude Esw ¼ 50 mV, scan increment dE¼ 0.15 mV, and starting potential Es ¼ 0:40 V.

Fig. 2. Forward (If ), backward (Ib), and net-SW (Inet) components of the square-wave voltammetric response of an n-octanol droplet containing 0.05 mol dm 3 dmfc attached to a paraffin impregnated graphite electrode which is immersed in 1 mol dm 3 KBr aqueous solution. The experimental conditions were same as in Fig. 1.

Table 2 Estimated values of the standard Gibbs energies of transfer and corresponding standard potentials of ion transfer from water to n-octanol of halide ions on the basis of electrostatic Born theory using Eq. (4)

Fig. 5. The correlation of the standard Gibbs energies of transfer from water to n-octanol for halide ions calculated on the base of electrostatic Born theory with those estimated by extrapolation.

Table 3 Estimated values of the standard Gibbs free energies and corresponding standard potentials of transfer from water to n-octanol of a series of anions

Fig. 6. SW voltammetric responses of an n-octanol droplet containing 0.05 mol dm 3 dmfc attached to a paraffin impregnated graphite electrode, which is immersed in 1 mol dm 3 aqueous solution of ðC6H5Þ4B ðTPBÞ, BF 4 ðTFBÞ, ClO 4 , NO 3 , and SCN . The other experimental conditions are the same as in Fig. 1.

Frequently asked questions

Q1. What are the contributions mentioned in the paper "An electrochemical method for determination of the standard gibbs energy of anion transfer between water and n-octanol" ?

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. 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. 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. 

Q2. What are the future works mentioned in the paper "An electrochemical method for determination of the standard gibbs energy of anion transfer between water and n-octanol" ?

To the best of their knowledge, this is the first experimental report of an electrochemical method to study the ion transfer across the waterjn-octanol interface. The employed methodology can be extended to study the hydrophobicity of various anionic species in the water/n-octanol system, which are of particular importance for different areas of chemistry, medicine, and pharmacology. The standard redox potential of the dmfcþ/dmfc couple is Eh dmfcþðOCÞ=dmfcðOCÞ ¼ 0:317 V vs. AgjAgCl. TPB and TFB are abbreviations for tetraphenylborate and tetrafluoroborate ions, respectively.