Gas to olive oil partition coefficients: a linear free energy analysis.

Literature values of gas to olive oil partition coefficients at 37 degrees C have been assembled for 218 compounds. Application of an Abraham linear free energy equation correlates 215 compounds with R2=0.981 and a standard deviation, SD, of 0.196 log units. One hundred and eight compounds were then used as a training set, and the resulting equation was used to predict the remaining 107 compounds with an average error of 0.025, an absolute average error of 0.150, and a standard deviation of 0.224 log units. The linear free energy equation shows that as a solvent olive oil is not very polar but is reasonably basic, although with a weaker hydrogen bond base than ethyl acetate or acetone, and has no hydrogen bond acidity. The coefficients for partition from the gas phase to biological phases such as blood and brain lie between those for water and olive oil, which explains why gas to biological phase partition can be described in an empirical way by a combination of gas to olive oil and gas to saline coefficients.