Gibbs Energies Of Transfer Research Articles

The determination of standard Gibbs energies of transfer of cations across the nitrobenzene|water interface using a three-phase electrode

A three-phase electrode consisting of a droplet of a nitrobenzene solution of iron(III) tetraphenyl porphyrine chloride (Fe(III)-TPP-Cl) attached to a graphite electrode and immersed in an aqueous electrolyte solution was applied to determine the standard Gibbs energies of transfer of cations between water and nitrobenzene. The reduction of Fe(III)-TPP-Cl prompts the transfer of the cations from the aqueous to the organic phase. The system is chemically and electrochemically reversible.

Electrochemical studies of vitamin K1 microdroplets: electrocatalytic hydrogen evolution.

The voltammetry of a basal-plane pyrolytic graphite electrode modified with a random ensemble of unsupported microdroplets of vitamin K, is investigated when the electrode is immersed in aqueous electrolytes. It is shown that in dilute acidic solutions, electroreduction occurs in a single two-electron two-proton process to yield the corresponding hydroquinone at the electrode\vitamin K1 microdroplet\aqueous-electrolyte three-phase boundary. On addition of ionic alkali-metal salts to the aqueous acidic phase, the electrochemical reduction of vitamin K1 to the quinol is accompanied by catalytic hydrogen evolution within and alkali-metal-cation insertion into the organic microdroplets. In strongly alkaline solutions, electrochemical reduction of vitamin K1 at the triple-phase junction is proposed as being a single two-electron process with concomitant uptake of alkali-metal cations in order to maintain electroneutrality within the oil phase. Surprisingly, the relative ease of cation insertion into the oil phase is demonstrated to be governed by the degree of ion-pair formation rather than by the Gibbs transfer energy of the cation across the liquid\liquid interface.

Comparative Assessment of the Solvating Powers of Solvents of Different Nature with Respect to Condensed Aromatic Hydrocarbons

The solubilities of anthracene, tetracene, 1,2-benzanthracene, chrysene, pyrene, perylene, α,α'-dinaphtyl, rubrene, and decacyclene in solvents of different nature and polarity (hydrocarbons and halogenated hydrocarbons, alcohols, ketones, ethers, and esters) were determined at 20±1°C. The distribution of benzene and naphthalene in the organic solvent-water system was studied. The Gibbs energy of transfer of aromatic hydrocarbons from n-octane to organic solvents was calculated.

Selective Recognition of Halide Anions by Calix[4]pyrrole: A Detailed Thermodynamic Study

Several analytical techniques ( 1 H NMR, conductance measurements, and titration calorimetry) have been used to assess the interaction of calix[4]pyrrole and halide anions in dipolar aprotic solvents (acetonitrile and N,N-dimethylformamide). Solubility data for calix[4]pyrrole in various solvents at 298.15 K were determined. These data were used to calculate the standard Gibbs energies of solution. Taking acetonitrile as the reference solvent, the transfer Gibbs energies of this ligand to various solvents were calculated. Chemical shift changes (Δδ) of the pyrrole proton relative to the free ligand resulting from the addition of the anion salts to the ligand in CD 3 CN at 298 K follow the sequence F - > Cl - > Br > I - . Conductance measurements were performed (i) to establish the stoichiometry of the anionic calix[4]pyrrole complexes and (ii) to assess the range of concentration at which the free and complex anion salts are predominantly in their ionic forms in acetonitrile and N,N-dimethylformamide at 298.15 K. Titration calorimetry was used to determine the stability constant, K s , (hence the standard Gibbs energy) and the enthalpy. Combination of Gibbs energy and enthalpy data yields the entropy of complexation. A linear correlation is found between the log K, and the Δδ values. The results show that calix[4]pyrrole is able to recognize selectively the halide anions in these solvents The selectivity of the ligand for one anion relative to another is quantitatively evaluated through the calculation of the selectivity factor. It is shown that the ligand behavior is representative of flexible ligands in which calix[4]pyrrole compete successfully with the solvent for the anion to an extent that the higher selectivity of the ligand is for the smallest anion (fluoride). The thermodynamics of complexation is discussed in terms of the solvation properties of the reactants and the products in acetonitrile and N,N-dimethylformamide.

Study of ionizable drugs transfer across the water/ 1,2-dichloroethane interface with phase volume ratio equal to unity using a three-electrode system

The electrochemical behavior of ionizable drugs (Amitriptyline, Diphenhydramine and Trihexyphenedyl) at the water/1,2-dichloroethane interface with the phase volume ratio (r = V-o/V-w) equal to 1 are investigated by cyclic voltammetry. The system is composed of an aqueous droplet supported at an Ag/AgCl disk electrode and it was covered with an organic solution. In this manner, a conventional three-electrode potentiostat can be used to study the ionizable drugs transfer process at a liquid/liquid interface. Physicochemical parameters such as the formal transfer potential, the Gibbs energy of transfer and the standard partition coefficients of the ionized forms of these drugs can be evaluated from cyclic voltammograms obtained. The obtained results have been summarized in ionic partition diagrams, which are a useful tool for predicting and interpreting the transfer mechanisms of ionizable drugs at the liquid/liquid interfaces and biological membranes.

Gibbs Energies of Transfer of Fluoride Salts from Water to Aqueous Alcohol Mixtures

Gibbs energy of transfer data for LiF and NaF from water to aqueous alcohol mixtures, obtained from solubility measurements, are examined via the Born equation. In spite of its well-known deficiencies, the simple Born model accounts for much of the observed variation of Δt G°(MF, w→w+ROH), particularly for NaF. This unexpected success of the Born model appears to result from the fortuitous cancellation of the donor and acceptor contributions to the solvation of the cations and anions by these closely related co-solvents. Examination of the deviations between the observed and calculated Δt G° values also suggests that they are partly due to uncompensated ion-pairing effects, especially for LiF.

Determination of Standard Gibbs Energies of Transfer of Organic Anions across the Water/Nitrobenzene Interface

ADVERTISEMENT RETURN TO ISSUEPREVCorrectionORIGINAL ARTICLEThis notice is a correctionDetermination of Standard Gibbs Energies of Transfer of Organic Anions across the Water/Nitrobenzene InterfaceŠ. Komorsky-Lovrić, K. Riedl, R. Gulaboski, V. Mirčeski, and F. ScholzCite this: Langmuir 2003, 19, 7, 3090Publication Date (Web):March 5, 2003Publication History Published online5 March 2003Published inissue 1 April 2003https://doi.org/10.1021/la0209233Copyright © 2003 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views300Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (17 KB) Get e-AlertsSUBJECTS:Anions,Energy,Energy transfer,Interfaces Get e-Alerts

Determination of the standard Gibbs energies of transfer of cations and anions of amino acids and small peptides across the water nitrobenzene interface.

The standard Gibbs energies of transfer of anions and cations of amino acids and small peptides across the water nitrobenzene interface were determined with the help of a novel electrochemical technique using three-phase electrodes. This is the first time that reliable data are reported for the anions of amino acids. The main result is that the standard Gibbs energies of transfer of the anion and cation of an amino acid are almost the same.

Influence of the presence of a gel in the water phase on the electrochemical transfer of ionic forms of β-blockers across a large water∣1,2-dichloroethane interface

The transfer of ionic species of three β-blockers (propranolol, sotalol and timolol) has been studied by cyclic voltammetry at a macroscopic water∣1,2-dichloroethane (1,2-DCE) interface. The aqueous solution has been gellified in order to study the effect of the gel on the transport properties of the drugs. The gelling agent also stabilizes the interface overcoming mechanical instability. The standard potential and standard Gibbs energy of transfer across the interface, the partition coefficient and the diffusion coefficient of each drug were determined in the presence of a gelled interface. The diffusion coefficients were shifted relative to those obtained at normal water∣1,2-DCE interfaces (free of gel).

Standard Gibbs energies of transfer of halogenate and pseudohalogenate ions, halogen substituted acetates, and cycloalkyl carboxylate anions at the water|nitrobenzene interface

Download options Please wait... Article information DOI https://doi.org/10.1039/B210356G Article type Paper Submitted 24 Oct 2002 Accepted 27 Jan 2003 First published 07 Feb 2003 Download Citation Phys. Chem. Chem. Phys., 2003,5, 1284-1289 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Standard Gibbs energies of transfer of halogenate and pseudohalogenate ions, halogen substituted acetates, and cycloalkyl carboxylate anions at the water|nitrobenzene interface R. Gulaboski, K. Riedl and F. Scholz, Phys. Chem. Chem. Phys., 2003, 5, 1284 DOI: 10.1039/B210356G To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Rubin Gulaboski Kai Riedl Fritz Scholz

Chemical Meaning of the Standard Free Energy of Transfer. 2. Use of van der Waals' Equation of State To Evaluate the Enthalpic and Entropic Contributions of Free Volume and Attractive Forces to Chemical Potentials

In a previous paper we derived an equation for the chemical potential of a nonideal, infinitely dilute solute in a van der Waals fluid. From this we also explored the change in the Gibbs energy of transfer of a solute between two van der Waals fluids and explored the effects of using different standard states on the interpretation of that Gibbs energy. In this paper, we extend that treatment by dissecting the equation for the chemical potential of an infinitely dilute solute in a van der Waals fluid to reveal the enthalpic and entropic origins of each term. We also provide a physical interpretation of each term based on its enthalpic and entropic contributions to the overall chemical potential. We conclude the paper with an exploration of the phenomenon of enthalpy/entropy compensation, using the van der Waals equation of state to derive a condition under which enthalpy/entropy compensation must be observed.

Gibbs energies of transfer of the proton from water into mixtures of water with chain multiple ethers: Equilibria involving changes of solvation of the proton

The solvent reorganisation around the proton has been investigated in mixtures of water with the dimethyl ethers of diethylene glycol and triethylene glycol using spectrophotometric observations on dilute solutions of 4-nitroaniline. The protonation occurs at only one basic site on the multiple ethers and the equilibrium constant is much greater than for simple ethers and alcohols. The Gibbs energy of transfer of the proton from water into the mixture is calculated. Comparing ΔGot(H+) with those for simple ethers and alcohols, it is concluded that the end ether group is the preferred basic site in the multiple ethers. ΔGot(H+) from this method are compared with ΔGot(H+) determined using the TATB method for a range of co-solvents: good agreement is obtained, except where enhanced structure is found in the water + co-solvent mixtures.

Relative molar Gibbs energies of cation transfer from a molecular liquid to ionic liquids at 298.15 K

Molar Gibbs energies of Ag+, Cu2+, Zn2+ and Cd2+ transfer from dimethylsulfoxide (DMSO), a reference molecular liquid, to a number of ionic liquids (IL), ΔtG(DMSO → IL), were obtained from M|Mn+ electrode potentials at 298.15 K. The ionic liquids consisted of various tetraalkylammonium cations and Cl−, Br−, BF4−, PF6− or N(CF3SO2)2− anions. The measured M|Mn+ (0.01 M, IL) potentials depend both on the tetraalkylammonium cation as well as on the anion. The transfer of cations from DMSO to ionic liquids brings about positive or negative changes of the molar Gibbs energy. The most important factor influencing the transfer molar Gibbs energy is the anionic component of the ionic liquid, which solvates the cation. In general, the molar Gibbs energy of cations in ionic liquids having N(CF3SO2)2− anion is lower than in those having halide or tetrafluoroborate anions.

Studies on the effect of substituents on the solvational behavior of 2-, 3- and 4-benzoic acids and their anions in ethanol+ water mixtures from conductometric and solubility measurements

The solvational behaviour of 2-, 3- and 4-substituted-chloro, -bromo, -iodo and -nitrobenzoic acids were examined from the solubility of the acids and the dissociation constants for the reaction, HA ⇄ H + + A - (where HA is substituted benzoic acid) determined conductometrically using Fuoss-Kraus method in ethanol + water mixtures (0-87 wt % of ethanol). The solubility values increase with the increase in hydrophobic character of the solvent mixtures and the changes depend both on the hydrophobic character and the dielectric constants of the solvent media. The sequence of the solubilities of the substituted acids are in the order: 2-compounds > 3-compounds > 4-compounds and -NO 2 > -Cl > -Br > -I. The Λ 0 -values of the substituted benzoic acids are almost similar but the order is Λ 0 (ortho) > Λ 0 (meta) > Λ 0 (para). Λ 0 -values of the nitrobenzoic acids are lower but the order is reversed. The Gibbs energies of transfer of anions were determined from the relation, ΔG 0 t (dissn.) = ΔG 0 t (H + ) + ΔG 0 t (A - ) - ΔG 0 t (HA) using the previously determined values of ΔG 0 t (H + ). The ΔG 0 t (A - ) values are found to be increasingly positive in aquo-organic mixtures and ΔG 0 t (A - ) values are usually in the order: 2-compounds > 3-compounds > 4-compounds. Nitrobenzoates differ from halobenzoates in their solvational behavior. The results are discussed in the light of change in the solute-solvent interactions of the substituted acids due to the change in dipole moments, polarizability, hydrogen-bonding and dispersion interactions. The effects of substitution on the interaction energies of anions were determined. Substituents change the interaction energies of neutral acids and their anions in a different way.

Solubilities and Gibbs transfer energies of thiolato, sulfenato, sulfinato and tris(ethylenediamine)cobalt(III) complexes, as well as of perchlorate,from acetonitrile into its mixtures with water

Information on the solvation of thiolato complex cations [Co(en)2(SCH2COO)]+ [Co(en)2(SCH2CH(COO)NH2)]+, [Co(en)2(SCH2CH2NH2)]2+, sulfenato complexes [Co(en)2(SOCH2COO)]+ [Co(en)2{SOCH2CH(COO)NH2}]+, [Co(en)2(SOCH2CH2NH2)]2+, the sulfinato [Co(en)2{SO2CH2CH(COO)NH2}]+, [Co(en)2(SO2CH2CH2NH2)]2+ as well as of [Co(en)3]3+ has been obtained from solubility measurements in MeCN–H2O mixtures at 298.2 K. The single-ion Gibbs energies of transfer of the CoIII complexes were derived from the solubilities of picrate and perchlorate salts for the full range of MeCN–H2O mixtures. Single-ion Gibbs energies of transfer for the perchlorate ion are given. The effects of the solvent mixtures were interpreted in the framework of chemical bond formation between the ions and the individual solvent molecules.

Determination of the Gibbs energies of transfer for some monovalent ions from water to triethylphosphite

The Gibbs energies of transfer, ΔtG0 for 9 monovalent ions from water to triethylphosphite are reported. The Gibbs energies of transfer have been determined from solubility product measurements of 1:1 salts. The extrathermodynamic tetraphenylarsonium tetraphenylborate (TATB) assumption has been applied in order to calculate the contribution from the individual ions. It is shown that soft electron-pair acceptors such as the silver(I) ion are strongly solvated in triethylphosphite, while hard electron acceptors with low charge density such as the alkali metal ions are almost equally solvated in triethylphosphite and water. The inorganic anions are so weakly solvated in triethylphosphite that solubility product measurements were not possible to perform with sufficient accuracy on salts with inorganic anions due to low solubilities. The only anions studied are tetraphenylborate and picrate.

Charge transfer across the water/nitrobenzene interface by three-electrode system

A droplet of aqueous solution containing a certain molar ratio of redox couple is first attached onto a platinum electrode surface, then the resulting drop electrode is immersed into the organic solution containing very hydrophobic electrolyte. Combined with reference and counter electrodes, a classical three-electrode system has been constructed. Ion transfer (IT) and electron transfer (ET) are investigated systematically using three-electrode voltammetry. Potassium ion transfer and electron transfer between potassium ferricyanide in the aqueous phase and ferrocene in nitrobenzene are observed with potassium ferricyanide/potassium ferrocyanide as the redox couple. Meanwhile, the transfer reactions of lithium, sodium, potassium, proton and ammonium ions are obtained with ferric sulfate/ferrous sulfate as the redox couple. The formal transfer potentials and the standard Gibbs transfer energy of these ions are evaluated and consistent with the results obtained by a four-electrode system and other methods.

Determination of the standard Gibbs energies of transfer of cations across the nitrobenzene|water interface utilizing the reduction of iodine in an immobilized nitrobenzene droplet

When a nitrobenzene (NB) droplet containing iodine is attached to a graphite electrode and immersed into a chloride containing aqueous (AQ) solution, the electrochemical reduction of iodine is accompanied by a transfer of chloride ions from NB to water. These chloride ions enter the NB phase in a preceding partition between the AQ and the NB phases, supported by formation of I 2Cl − ions in NB and accompanied by the transfer of stoichiometric amounts of cations. The overall electrode reaction is of CE rev type, where C refers to the preceding chemical step forming I 2Cl −, and E rev refers to the reversible reduction of iodine at the graphite|NB interface and the simultaneous transfer of chloride from NB to water. If the chloride concentration in NB is insufficient to compensate by leaving the NB the amount of electrochemically produced iodide, a second voltammetric signal occurs at more negative potentials due to the transfer of iodide from NB to water. The kinetics and thermodynamics of the preceding chemical step C, determine the voltammetric behaviour of the system in such way that the ratio of peak currents of the first and second signals depends linearly on the Gibbs energy of transfer of the co-partitioned cations. The method was validated for cations of known Gibbs energies of transfer, and it was applied to cations of amino acids.

A speciation-based model for mixed-solvent electrolyte systems

A comprehensive model has been developed for the calculation of speciation, phase equilibria, enthalpies, heat capacities and densities in mixed-solvent electrolyte systems. The model incorporates chemical equilibria to account for chemical speciation in multiphase, multicomponent systems. For this purpose, the model combines standard-state thermochemical properties of solution species with an expression for the excess Gibbs energy. The excess Gibbs energy model incorporates a long-range electrostatic interaction term expressed by a Pitzer–Debye–Hückel equation, a short-range interaction term expressed by the UNIQUAC model and a middle-range, second virial coefficient-type term for the remaining ionic interactions. The standard-state properties are calculated by using the Helgeson–Kirkham–Flowers equation of state for species at infinite dilution in water and by constraining the model to reproduce the Gibbs energy of transfer between various solvents. The model is capable of accurately reproducing various types of experimental data for systems including aqueous electrolyte solutions ranging from infinite dilution to fused salts, electrolytes in organic or mixed, water+organic, solvents up to the solubility limit and acid–water mixtures in the full concentration range.

Determination of Standard Gibbs Energies of Transfer of Organic Anions across the Water/Nitrobenzene Interface

The oxidation of decamethylferrocene dissolved in a nitrobenzene droplet and attached to a graphite electrode that is immersed in an aqueous electrolyte solution provides the basis to determine the standard Gibbs energies of transfer of simple organic anions, such as those of aliphatic and aromatic mono- and dicarboxylic acids, and phenols. The data are rationalized on the basis of the constitution of the compounds.