Prediction of Partition Coefficient log P

The measurement of the solubility of drugs in polar and non-polar media is very important in the pharmaceutical field. One method proposed to describe this solubility is the partition coefficient between octanol and water. The mathematical calculation of an octanol-water partition coefficient from values for functional groups was first proposed by Hansch et al. as Hansch s n constants,1 and was later developed by Rekker as hydrophobic fragmental constants (logP).2 This method was further improved by the use of molecular connectivities.17 The prediction of logP values can be performed by either a computer program or by manual calculation. For example, approximate partition coefficients (log P) have been calculated by Rekker s method  

A part of his fragmental constant tables is given in Table 6.1. (The predicted log P values are summarized in Table 6.4.) 

Attempts have also been made to determine octanol-water partition coefficients empirically using liquid chromatography by comparison of retention times with those of compounds of known logP.3-12 

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