COMPARISON OF FOUR METHODS OF PREDICTING NEWLY MEASURED OCTANOL/WATER COEFFICIENTS (LOG Kow) FOR HETEROCYCLIC NITROGEN COMPOUNDS AND THE PARTITION MECHANISM

Log Kow values for 14 heterocyclic nitrogen compounds (by traditional shake-flask method) were reported. Reverse phase–high-performance liquid chromatography (RP-HPLC) method and three estimation models—linear solvation energy relationship, molecular connectivity indices (MCIs), and quantum chemical descriptors—were used to study the partition mechanism and to establish the correlations of the models with the measured log Kow values by stepwise variable regression. Research on the partition mechanism showed that the molecular bulk properties and the hydrogen bond interaction were the most important factors influencing the partition process. Comparison of the quality of the models was made among the four methods. According to the simplicity of the method, the availability of the descriptors, and the closeness of correlation with the measured log Kow values, the RP-HPLC method was not satisfactory, while the MCIs method introducing the non–disperse force factor was the most satisfactoy. Keywords—n-Octanol/water partition coefficient Heterocyclic nitrogen compounds Partition mechanism Quantitative structure–activity relationship