Thermodynamic Functions Of Transfer Research Articles

Heats of solution of cyclohexanol in benzene solutions of tri-n-octylammonium bromide and derived thermodynamic functions of transfer from benzene

The integral heats of solution of cyclohexanol (up to 0.10 mol kg −1) in benzene solutions of tri-n-octylammonium bromide (up to 0.25 mol kg −1) were measured at 298.15 K. It was found that the partial molar enthalpy of solution of cyclohexanol is concentration independent at a definite concentration of tri-n-octylammonium bromide. The heat of solution was interpreted by the McMillan-Mayer theory and the enthalpic interaction coefficients were calculated. The standard thermodynamic functions of transfer of cyclohexanol from benzene to benzene solutions of tri-n-octylammonium bromide were calculated at 298.15 K. The standard enthalpy of transfer for cyclohexanol is almost compensated by the standard entropy of transfer in calculation of the Gibb's free energy of transfer. The cross pair interaction coefficient was ascribed to complex formation between the hydroxylic proton of cyclohexanol and the bromide ion of tri-n-octylammonium bromide via hydrogen bonding.

Kinetics of oxidation ofcis-, andtrans-chlorobis(ethylenediamine)isothiocyanatocobalt(III)ion with peroxodisulphate in aqueous alcoholic mixtures

The effect of organic cosolvent on the rate constants and activation parameters of oxidation of coordinativelybound thiocyanate with peroxodisulphate was investigated in mixtures of water with methanol,i-propanol andt-butanol. The thermodynamic transfer functions, corresponding to the transfer of reactants and activated complex from water to the solvent mixtures were evaluated from kinetic measurements and from the solubilities of corresponding salts. The experimental results are interpreted in terms of the solvation of both the initial state and the activated complex.

Solvent effect on activation parameters for the neutral hydrolysis of phenyl trifluoroacetates in aqueous acetonitrile

Rates of neutral hydrolysis of phenyl, 4-nitrophenyl, and 2,4-dinitrophenyl trifluoroacetates in acetonitrile–water mixtures (xMeCN= 0.39–0.97) have been measured. The free energies of activation increase smoothly upon increasing the acetonitrile content of the medium while the enthalpies and entropies of activation show a more complex but partially compensating behaviour. For phenyl trifluoroacetate both ΔH‡ and ΔS‡ pass through an inflexion point around xMeCN= 0.6. For 4-nitrophenyl and 2,4-dinitrophenyl trifluoroacetates a minimum value possibly occurs both in ΔH‡ and ΔS‡ around xMeCN= 0.9–0.95, but it is clearly observed in ΔH‡ at xMeCN= 0.92 for the former ester and in ΔS‡ at xMeCN= 0.94 for the latter ester. The activation parameters are discussed in terms of solvent structure. The extreme values are mainly attributed to changes in the thermodynamic functions of transfer of the transition state of the hydrolysis reaction from water to acetonitrile–water mixtures.

Solvent effects on the thermodynamics of aquocobalamin chloride and model compounds in dioxane–water mixtures

The solubilities of aquocobalamin chloride and eight other cobalt(III) complexes have been measured in dioxane–water mixtures. For aquocobalamin chloride, aquanitrocobaloxime and aquamethylcobaloxime solubilities have also been measured as a function of temperature. The transfer thermodynamic functions ∂mG°, ∂mH° and ∂mS° have been calculated. The results may be accounted for in terms of the cavity energy and specific interactions. A difference has been found between the transfer functions of the aquocobalamin cation in dioxane–water mixtures and those in acetonitrile–water mixtures.

Thermodynamic functions of transfer of single ions from water to nonaqueous and mixed solvents: Part 4 - The selection of extra thermodynamic assumptions

Abstract

The distribution of branched octanols between dodecane and water

The distribution of four branched chain octanols, 3-ethyl-3-hexanol, 4-ethyl-3-hexanol, 2-ethyl-4-methylpentanol, and 4-octanol, has been measured between dodecane and water. Measurements were made at alcohol concentrations in the dodecane of less than 0.1 mol/dm3, and as a function of temperature from 10 °C to 35 °C. From these distribution data, standard thermodynamic functions for transfer were calculated. Standard Gibbs energies of transfer from water to dodecane at 25 °C were in the range −14.1 to −15.1 kJ/mol, whereas the standard enthalpies of transfer at 25 °C varied from 29 to 39 kJ/mol. Thus, the change in the standard enthalpy tends to inhibit transfer, but a large standard entropy of transfer results in dodecane being the favoured phase.

Thermodynamic functions of transfer of single ions from water to nonaqueous and mixed solvents: Part 3 - Standard potentials of selected electrodes

Abstract

Thermodynamic functions of transfer of single ions from water to nonaqueous and mixed solvents: Part 2 - Enthalpies and entropies of transfer to nonaqueous solvents

Abstract

Chemical equilibrium model for the thermodynamic properties of mixed aqueous micellar systems: Application to thermodynamic functions of transfer

Mixed micelles can be formed in water between various pairs of hydrophobic solutes such as surfactants, alcohols and hydrocarbons. These systems can often be studied through the thermodynamic functions of transfer of one of the solutes, usually kept near infinite dilution, from water to an aqueous solution of the other solute. When mixed micelles are formed, these functions change significantly, and often go through extrema, in the region where the binary system micellizes or undergoes some microphase transition.Three main effects are responsible for the observed trends: pair-wise interactions between both solutes in the monomeric form, a distribution of the reference solute between the aqueous and micellar phases and a shift in the monomer-micelle equilibrium in the vicinity of the reference solute. Simple equations can be derived for these three effects which can account for the sign and magnitude of the observed trends using parameters which are derived for the most part from the two binary systems.

Free Energy, Enthalpy, and Entropy Changes of Mixing of Aqueous Solutions of d-Glucose and Tetraalkylammonium Bromide at 25 °C

Abstract Changes of free energy and enthalpy of mixing of aqueous solutions of d-glucose and tetraalkylammonium bromide were measured at 25 °C by isopiestic method and calorimetry, and excess thermodynamic quantities and transfer functions were calculated. All transfer functions were positive and mutual salting-out was observed. The positive value of free energy of transfer of tetrabutylammoniun bromide from water to aqueous d-glucose solution comes from the predominance of enthalpic term over entropic term. These results are interpreted in terms of the structural incompatibility of hydration cospheres around these two kinds of solutes.

Thermodynamic functions of transfer of single ions from water to nonaqueous and mixed solvents: Part I - Gibbs free energies of transfer to nonaqueous solvents

Abstract

Standard potentials of the Ag/AgCl electrode in water + 2-ethoxy ethanol mixtures

The standard potential of the Ag/AgCl electrode in a water+2-ethoxy ethanol system has been determined at 25, 30, 35, 40 and 45°C at various compositions of 2-ethoxy ethanol varying from zero to ⋍70 wt%. The effect of solvent composition on Em0 is studied and the results interpreted in terms of the breakdown of the water structure by the additon of organic solvent. From the values of the mean activity coefficient of HCl calculated in each solvent composition, the primary, secondary and total medium effects are evaluated. The primary medium effect shows an increase with increase of 2-ethoxy ethanol content. The relative partial molal heat content L¯2 of HCL is computed from the variation of the mean activity coefficient γ± with temperature. The standard thermodynamic functions of transfer (ΔGt0, ΔHt0 and ΔSt0) of 1 mol of HCl in its standard state from water to water+2-ethoxy ethanol mixtures are calculated. These thermodynamic functions are divided into two parts: (1) electrostatic, and (2) non-electrostatic (chemical), and the results are discussed on the basis of water structure.

Standard potentials of the Ag/AgCl electrode in water+2-ethoxy ethanol mixtures

The standard potential of the Ag/AgCl electrode in a water+2-ethoxy ethanol system has been determined at 25, 30, 35, 40 and 45°C at various compositions of 2-ethoxy ethanol varying from zero to ⋍70 wt%. The effect of solvent composition on E m 0 is studied and the results interpreted in terms of the breakdown of the water structure by the additon of organic solvent. From the values of the mean activity coefficient of HCl calculated in each solvent composition, the primary, secondary and total medium effects are evaluated. The primary medium effect shows an increase with increase of 2-ethoxy ethanol content. The relative partial molal heat content L¯ 2 of HCL is computed from the variation of the mean activity coefficient γ ± with temperature. The standard thermodynamic functions of transfer (Δ G t 0, Δ H t 0 and Δ S t 0) of 1 mol of HCl in its standard state from water to water+2-ethoxy ethanol mixtures are calculated. These thermodynamic functions are divided into two parts: (1) electrostatic, and (2) non-electrostatic (chemical), and the results are discussed on the basis of water structure.

Thermodynamic transfer functions of nonionic solutes between immiscible liquid phases. Transfer of some secondary alcohols from n-octane to water at 298.15 K

Thermodynamic transfer functions of nonionic solutes between immiscible liquid phases. Transfer of some secondary alcohols from n-octane to water at 298.15 K

Thermodynamics of transfer of sorbitol and mannitol from water to aqueous solutions of urea, guanidine hydrochloride and sodium chloride

Integral enthalpies of solution at 298.15 and 308.15 K and densities at 298.15 K for sorbitol and mannitol in aqueous solutions of urea (2, 4 and 6 mol kg–1), guanidine hydrochloride (2 and 4 mol kg–1) and sodium chloride (2 and 4 mol kg–1) have been determined. These data have been used to derive thermodynamic functions (viz. enthalpy, heat capacity and partial molal volumes) for transfer from water to aqueous solutions of urea, guanidine hydrochloride and sodium chloride. The thermodynamic data have been rationalized in terms of polyol–cosolute interactions. The difference in the behaviour of sorbitol and mannitol has been explained in terms of a specific hydration model.

Thermodynamic properties of copper sulphate in dioxan + water mixtures from electromotive-force measurements

Electromotive-force measurements of the cell Cu-Hg|CuSO4(m), dioxan (X)|Hg2SO4(s)|Hg have been made at 288, 298, 308 and 318 K for solvent compositions X= 10, 20, 30 and 40%(w/w) of dioxan. These have been used to evaluate the standard potentials of the cell, the mean activity coefficient of copper sulphate (molal scale) and the thermodynamic functions of transfer of copper sulphate from water to the respective dioxan + water media. The results have been interpreted in terms of solute–solvent interactions.

Thermodynamics of transfer of non-ionic solutes between immiscible liquid phases. I. Transfer of normal alcohols fromn-octane to water at 25°C

A recently developed calorimetric method has been employed to estimate the thermodynamic functions for transfer of 1-propanol, 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol from n-octane to water at 25°C. A linear correlation for ΔGto as a function of the number of carbon atoms of the alchohol molecule has been found but for ΔHto and ΔSto the dependence gave well defined minima.

Microheterogeneity in aqueous-organic mixtures: thermodynamic transfer functions for benzene from water to 2-propanol aqueous systems at 25�C

The solubilities, enthalpies of solution, heat capacities, densities and ultrasonic velocities of benzene in 2-propanol-water mixtures were measured at 25°C. The apparent molal volumes, heat capacities and isentropic compressibilities and the free energies, enthalpies and entropies of transfer of benzene were calculated. The benzene concentration is sufficiently low that all thermodynamic quantities can be considered in the standard state. All these functions show large changes in the aqueous end. Large extrema are observed for 2-propanol mole fractions (XP) near 0.08, and at higher XP the functions rapidly tend to the values in pure 2-propanol. The free energy of transfer of benzene from water to alcohol-water mixtures decreases linearly with the alcohol concentration up to XP of 0.07 and then more abruptly. On the other hand, at low temperature, this free energy becomes positive at low XP. These data are consistent with the existence of microphases in 2-propanol-water mixtures for Xp>0.1. At low XP benzene is in an aqueous medium but beyond this critical region dissolves preferentially in the organic microphases. Benzene also enhances the formation of 2-propanol microphases and this leads to the observed extrema near Xp=0.08.

On the use of thermodynamic transfer functions for the study of the effect of additives on micellization: Volumes and heat capacities of sodium octanoate systems

Volumes and heat capacities of transfer were used to study the effect of various additives on micellization. The reference surfactant in this study was sodium octanoate and the other components were NaCl, sodium formate, sodium acetate, sodium perfluoroacetate, n-butoxyethanol, sodium decanoate, and sodium perfluorooctanoate. The heat capacities and volumes were measured with a flow microcalorimeter and a flow densimeter. In the case of NaCl and n-butoxyethanol the converse transfer functions were measured, i.e., the transfer of sodium octanoate from water to the binary solution. This work shows that the simple electrolytes enhance the micellization by salting out the monomers, n-butoxyethanol comicellizes with the surfactant and so does sodium decanoate. With perfluorooctanoate two different types of mixed micelles seem to coexist: one rich in hydrosurfactant and one in perfluorosurfactant.

Calorimetric method for the direct evaluation of the thermodynamic functions for the transfer of non-ionic solutes between immiscible liquid phases

A simple method is proposed which allows a straight-forward evaluation of the thermodynamic functions of transfer by using the results of calorimetric mixing experiments.