Partition of compounds from gas to water and from gas to physiological saline at 310 K: Linear free energy relationships

Data have been assembled on gas to water partition coefficients for 374 compounds at 310 K. It is shown that an Abraham solvation equation with five descriptors can be used to correlate 350 such values, as log KW(310), with R2 = 0.994 and S.D. = 0.154 log units. Division into a training set and a test set shows that there is no bias in predictions and that predictive capability of the equation is 0.16 log units. Use of indicator variables allows the inclusion of polyaromatic hydrocarbons and polychlorobiphenyls, and for a total data set of 374 compounds R2 = 0.993 and S.D. = 0.163 log units. For partition from the gas phase into physiological saline (0.9% sodium chloride) at 310 K, a similar equation with five descriptors correlates values for 257 compounds with R2 = 0.989 and S.D. = 0.180 log units. For 135 overlapping compounds for which both log KW(310) and log KW(saline) are known, the average error is only 0.032 log unit, suggesting that the two data sets can be combined. For the total of 631 data points, an equation with five descriptors plus indicator variables for polyaromatic hydrocarbons and polychlorobiphenyls has R2 = 0.992 and S.D. = 0.177 log units.