Determination of octanol/water partition coefficients for hydrophobic organic chemicals with the “slow-stirring” method

Abstract

Experimental data are presented on octanol/water partition coefficients for 70 hydrophobic organic chemicals that were determined with a “slow-stirring” method. With this method, log Kow values can be obtained relatively easily, with high reproducibility and low standard deviations. For compounds with log Kow values of less than 4.5, the experimental data agree well with literature data based on the classical shake-flask method. For more hydrophobic compounds, deviations occur because of the formation of octanol emulsions in the shake-flask procedure. In general, there is reasonable agreement with literature data obtained by reversed-phase HPLC or the generator-column method, although substantial deviations do occur for some individual compounds, especially the higher-chlorinated ortho-substituted polychlorinated biphenyl (PCB) congeners. For chlorobenzenes, chloroanilines and PCBs, substituent constants (π) are calculated. With these π values, partition coefficients for these compounds can be estimated simply by calculation.