We present an extended QSPR modeling of solubilities of about 500 substances in series of up to 69 diverse solvents. The models are obtained with our new software package, CODESSA PRO, which is furnished with an advanced variable selection procedure and a large pool of theoretically derived molecular descriptors. The squared correlation coefficients and squared standard deviations (variances) range from 0.837 and 0.1 for 2-pyrrolidone to 0.998 and 0.02 for dipropyl ether, respectively. The predictive power of the models was verified by using the "leave-one-out" cross-validation procedure. The QSPR models presented are suitable for the rapid evaluation of solvation free energies of organic compounds. BACKGROUND TO THE PRESENT SERIES OF PAPERSSolubility is of the utmost significance in numerous areas of human endeavor and interest. Solubility in water is fundamental to environmental issues such as pollution, erosion, and mass transfer. Solubility in organic solvents forms much of the basis of the chemical industry. Solubility determines shelf life and cross contamination. It is critically linked to bioavailability and thus to the effectiveness of pharmaceuticals, biodegradation, suitability of gaseous anesthetics, blood substitutes, oxygen carriers, etc. Toxicity is critically dependent on solubility.Very extensive studies have been carried out on the solubilities of various solute-solvent pairs resulting in diverse theories of solute-solvent interactions that form the basis of our knowledge for the understanding of solubility. 1 These theories are based on concepts ranging from quantitative analysis to statistical mechanics and quantum mechanics. Quantitative treatments of solute-solvent interactions in series of compounds have gained wide attraction and have led to various models for explaining solute-solvent behavior. 2 Most of this work has involved studying a series of solutes dissolved in a single solvent. There are some instances in which the solubilities of a solute in a series of solvents have been examined, as reviewed elsewhere. 3,4 Many of the previous studies provide valuable contributions to the understanding of the general phenomena of solute-solvent interactions. In depth comparisons of published data series have revealed that many gaps exist, which render impossible any general comparison of solvent-solute pairs utilizing only experimental data. Therefore we have proposed the combination of quantitatiVe structure-property/actiVity relationship analysis and subsequent principal component analysis for the general treatment of solubility. 5 A common procedure in quantitative structure-property/ activity relationships (QSPR/QSAR) analysis is the application of variable selection methods such as stepwise forward selection, 6,7 genetic algorithms, 8,9 and simulated annealing 10,11 for the reduction of descriptor space in order to keep the only most influential descriptors for the prediction of a property (in the present instance solubility). In this first version of our general treatment of solubility w...

Partition coefficients of 51 organic compounds in two ionic liquids (IL), 1-ethyl-3-methylimidazolium dicyanamide and trimethylhexylammonium bis((trifluoromethyl)sulfonyl)amide, were measured using inverse gas chromatography from (322.5 to 352.5) K. These partition coefficients were converted into water-to-IL partition coefficients using the corresponding gas-to-water partition coefficients. Both sets of partition coefficients were analyzed using the Abraham solvation parameter model with cation-specific and anionspecific equation coefficients. The derived equations correlated the experimental gas-to-IL and water-to-IL partition coefficient data to within (0.12 and 0.14) log units, respectively.

ABSTRACT:1 H NMR chemical shifts have been obtained in the solvents deuterochloroform and dimethyl sulfoxide. The difference in the chemical shifts of an OH or NH group in these two solvents, Δδ = δ(DMSO) − δ(CDCl 3 ), can be converted into the hydrogen bond acidity, A, of the group using the equation A = 0.0065 + 0.133Δδ. The NMR A value, A NMR , can be used as a quantitative assessment of intramolecular hydrogen bonding. We list values of Δδ and A NMR for 55 compounds containing an OH group and 60 compounds with an NH group. For the hydroxy compounds, if A > 0.5 then the OH group is not part of an intramolecular hydrogen bond, but if A < 0.1 then the OH group forms part of an intramolecular hydrogen bond. For NH compounds, if A > 0.16 the NH group is not part of an intramolecular hydrogen bond, and if A < 0.05 the NH group is part of an intramolecular hydrogen bond. No comparison compounds are needed, and the method is extremely simple. We further show how it is possible to relate intramolecular hydrogen bonding to the actual effect on values of a number of physicochemical, environmental, and biochemical properties. ■ INTRODUCTION Shalaeva et al.1 have recently shown that the presence of an intramolecular hydrogen bond (intraHB) in a molecule can considerably alter the properties of a molecule. These include properties relevant to drug design such as solubility, permeability, and partition. It is therefore important to be able to identify molecules that possess intraHBs and, if possible, to assess the effect of an intraHB on the molecular properties. Testa and co-workers 2−5 were the first to show that the effect of intraHBs could be observed in water−solvent partition coefficients (as log P) and particularly in differences between partition coefficients in water−octanol and water−aprotic solvent systems. They set out differences in log P for water− octanol and water−heptane partitions (eq 1) and showed that intraHBs greatly reduce the value of Δ(log P) oct−hept . They also observed similar effects due to intraHBs in other water−octanol and water−solvent systems.4,5 Leo 6 used octanol and chloroform as the two solvent systems in order to calculate the hydrogen bond acidity of a solute, and Feng et al. 7 used dibutyl ether and cyclohexane as the solvent systems to calculate solute hydrogen bond acidity.

Gas to RTIL (room temperature ionic liquid) partition coefficients have been compiled for a series of solutes for a number of RTILs. These partition coefficints can be converted into water to RTIL partition coefficients using corresponding gas to water partition coefficients. The gas to RTIL and water to RTIL partition coefficients have been correlated through the Abraham solvation equations to yield equations that can be used for the prediction of further partition coefficients. The coefficients in the Abraham solvation equations yield quantitative information on solute-solvent (RTIL) interactions. It is shown that the RTILs have solvation properties quite close to those for polar aprotic organic solvents. The equations for gas to RTIL and gas to solvent partition coefficients can be used to predict the selectivity of RTILs and organic solvents towards pairs of solutes. It is shown that the selectivity of RTILs is not extraordinary, but is about the same as the selectivity of polar aprotic solvents.

Previously reported ion-specific equation coefficients for both the Abraham general solvation model and Goss modified Abraham model are updated using recently measured activity coefficient, gas chromatographic retention factor, and solubility data for solutes dissolved in room temperature ionic liquids (RTILs). Reported for the first time are equation coefficients for 1-propyl-2,3-dimethylimidazolium cation, and octylsulfate and thiocyanate anions. In total nine sets of cation-specific and eight sets of anion-specific equation coefficients have been determined for each model. The derived correlations describe the 976 experimental gas-to-RTIL partition coefficients to within a standard deviation of 0.12 log units and the 955 experimental water-to-RTIL partitions to within a standard deviation of 0.15 log units.

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Water-to-polydimethylsiloxane (PDMS) and gas-to-PDMS sorption coefficients have been compiled for 170 gaseous and organic solutes. Both sets of sorption coefficients were analyzed using the Abraham solvation parameter model. Correlations were obtained for both "dry" headspace solid-phase microextraction and conventional "wet" PDMS coated surfaces. The derived equations correlated the experimental water-to-PDMS and gas-to-PDMS data to better than 0.17 and 0.18 log units, respectively. In the case of the gas-to-PDMS sorption coefficients, the experimental values spanned a range of approximately 11 log units.