Variation with temperature of octanol/water partition coefficient for the homologous series from benzene to propylbenzene

Variation of octanol/water partition coefficient, log K ow , with temperature is seldom reported in the literature. A precise method for the evaluation of log K ow has been developed and the values of this parameter were measured for benzene, toluene, ethylbenzene, and n‐propylbenzene at six temperatures between 15 and 60°C. The procedure is based on a direct “shake flask” method, but utilizes a gas chromatography with mass spectrometry method for the measurement of the concentration of analytes in the water and octanol extracts. The results indicate that log K ow values for these analytes have only small variations with the temperature, and that this variation does not depend linearly on 1/ T . The results for log K ow in the evaluated temperature interval are close to the values reported in the literature for log K ow at 25°C. The variations of log K ow were found to be small and are non‐linear in 1/ T . Based on these variations the enthalpy ΔH 0 and entropy ΔS ° for the partition process were calculated. The obtained values for ΔH 0 and ΔS 0 indicated that for temperatures below about 40°C the process is entropy‐driven and does not involve large Gibbs free energies.