In this work, we report the infinite dilution activity coefficients (γ 1,2 ∞ ) of 39 to 43 diverse organic solutes dissolved in three 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids (IL) homologues bearing propyl, butyl, and pentyl n-alkyl side chains, respectively, as determined by inverse gas chromatography at temperatures from 323 K to 343 K. The organic solutes include various (cyclo)alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, thiophene, ethers, nitroalkanes, and ketones. The measured retention data were further transformed to gas-to-IL and water-to-IL partition coefficients using established thermodynamic approaches based upon the corresponding gas-to-water partition coefficients of the test solutes. Both sets of partition coefficients were interpreted with a modified form of the basic Abraham general solvation parameter model. The mathematical correlations obtained by regression analysis backcalculated the observed gas-to-IL and water-to-IL partition coefficient data to within average standard deviations of 0.104 and 0.136 log units, respectively.

Data have been compiled from the published literature on the partition coefficients of solutes and vapors into anhydrous sulfolane. The logarithms of the water-to-sulfolane partition coefficients, log P, and gas-to-sulfolane partition coefficients, log K, were correlated with the Abraham solvation parameter model. The derived correlations described the observed log P and log K values for solutes dissolved in sulfolane to within average standard deviations of 0.14 log units or less. The log P correlation was extended to include the partition of ions by inclusion of a cation-solvent and an anion-solvent term.

Experimental solubilities are reported for benzoin dissolved in 1 chloroalkane, 15 alcohols, 5 aromatic hydrocarbons, 5 alkyl acetates, 5 alkoxyalcohols and 3 ethers at 298.15 K. The measured solubility data were mathematically correlated with the Abraham solvation parameter model. The solute descriptors that were calculated for benzoin describe the experimental molar solubility data to within an overall average standard deviation of 0.097 log units.

Experimental data have been compiled from the published literature on the partition coefficients of solutes and vapors into o-xylene, m-xylene and p-xylene at 298 K. The logarithms of the water-to-xylene partition coefficients, log P, and gas-to-xylene partition coefficients, log K, were correlated with the Abraham solvation parameter model. The derived mathematical expressions described the observed log P and log K data for the three xylene isomers to within average deviations of 0.14 log units or less. Key words and phrasesPartition coefficients, xylene solvents, Abraham model correlations ________________________________________________________________________ *To whom correspondence should be addressed. (E-mail: acree@unt.edu) 2 IntroductionLiquid-liquid extraction affords a convenient experimental means for separating synthesized organic materials from reaction solvent media, and for pre-concentrating chemicals in unknown liquid samples prior to quantitative analyses. Extraction methods are based on solute partitioning in a biphasic liquid system containing two or more solvents having limited mutual solubility. Molecular interactions between the dissolved solute(s) and surrounding extraction solvents determine the solute recovery factor and separation efficiency. Considerable attention has been given in recent years to developing methods for selecting the best biphasic partitioning system to achieve a desired chemical separation.In many previous studies [1-8], we have shown that two general linear free energy Abraham model correlations, equations 1 and 2, can be used to mathematically describe the transfer of neutral solutes from water to organic solvents and from the gas phase to organic solvents log P = c p + e p ·E + s p ·S + a p ·A + b p ·B + v p ·Vlog K = c k + e k ·E + s k ·S + a k ·A + bk·B + l k ·LThe dependent variables in eqns. 1 and 2 are the logarithm of the water-to-organic solvent partition coefficient, log P, and the logarithm of the gas-to-organic solvent partition coefficient, log K, for a series of solutes. The independent variables, or solute descriptors, are properties of the neutral solutes as follows: [9,10] E is the solute excess molar refraction in cm 3 mol -1 /10, S is the solute dipolarity/polarizability, A is the overall solute hydrogen bond acidity, B is the overall solute hydrogen bond basicity, V is McGowan's characteristic molecular volume in cm 3 mol -1 /100 and L is the logarithm of the gas to hexadecane partition coefficient measured at 298 K.

Experimental data have been compiled from the published chemical and engineering literature pertaining to the infinite dilution activity coefficients, gas solubilities and chromatographic retention factors for solutes dissolved in ionic liquid (IL) solvents. Included in the compilation are chromatographic retention factors for forty-five solutes on a 1-butyl-1-methylpyrrolidinium tricyanomethanide ionic liquid gas-liquid chromatographic stationary phase. The published experimental data were converted to gas-to-IL and water-to-IL partition coefficients, and correlated with the ion-specific equation coefficient version of the Abraham general solvation 2 model. Ion-specific equation coefficients were calculated for 40 different cations and 16 different anions. The calculated ion-specific equation coefficients describe the experimental gas-to-IL and water-to-IL partition coefficient data to within 0.123 and 0.149 log units, respectively.

Infinite dilution activity coefficients (γ 1,2 ∞ ) are reported for 31 and 40 diverse organic solutes dissolved in trihexyl(tetradecyl)phosphonium L-lactate and trihexyl(tetradecyl)phosphonium (1S)-(+)-10-camphorsulfonate, as determined by inverse gas chromatography at temperatures from 323 K to 373 K. The measured retention data were further transformed to gas-to-ionic liquid and water-to-ionic liquid partition coefficients using standard thermodynamic expressions based upon measured values for corresponding gas-to-water partition coefficients of the test solutes. Both sets of partition coefficients were interpreted using an ion-specific equation coefficient form of the basic Abraham general solvation parameter model. Finally, ion-specific equation coefficients were calculated for the chiral L-lactate and (1S)-(+)-10-camphorsulfonate anions.

Experimental data have been compiled from the published literature on the partition coefficients of solutes and vapors into ethylbenzene and toluene at 298 K. The logarithms of the water-to-ethylbenzene and water-to-toluene partition coefficients, log P, and gas-to-ethylbenzene and gas-to-toluene partition coefficients, log K, were correlated with the Abraham solvation parameter model. The derived mathematical expressions described the observed log P and log K data for the two aromatic hydrocarbon solvents to within average deviations of 0.13 log units or less.

Data have been assembled from the published literature on the enthalpies of solvation for 91 organic vapors and gaseous solutes in 2-propanol, for 73 gaseous compounds in 2-butanol, for 85 gaseous compounds in 2-methyl-1-propanol and for 128 gaseous compounds in ethanol. It is shown that an Abraham solvation equation with five descriptors can be used to correlate the experimental solvation enthalpies to within standard deviations of 2.24 kJ/mole, 1.99 kJ/mole, 1.73 kJ/mole and 2.54 kJ/mole for 2-propanol, 2-butanol, 2-methyl-1-propanol and ethanol, respectively. The derived correlations provide very accurate mathematical descriptions of the measured enthalpy of solvation data at 298 K, which in the case of ethanol span a range of 136 kJ/mole. Division of the experimental values into a training set and a test set shows that there is no bias in predictions, and that the predictive capability of the correlations is better than 3.5 kJ/mole.