logP

LogP, or log Kow, is the base-10 logarithm of the partition coefficient P of a compound between n-octanol and water at equilibrium. P is defined as the concentration of the compound in octanol divided by its concentration in water, and logP is typically reported for the neutral form of the molecule at 25 °C with the octanol phase water-saturated. LogP is a measure of lipophilicity or hydrophobicity and is widely used to predict properties such as membrane permeability, oral absorption, and environmental fate.

In medicinal chemistry and pharmacology, higher logP generally implies greater membrane permeability but poorer aqueous solubility, influencing absorption, distribution, and dosing considerations. In environmental science, logP helps assess persistence and potential for bioaccumulation, with high values often associated with hydrophobic, persistent organics.

Methods: logP can be determined experimentally by the shake-flask method or inferred by chromatographic or spectrometric techniques, though ionization can complicate measurements for weak acids or bases. Computational predictions (fragment constants, machine learning models) estimate logP from molecular structure. It is important to distinguish logP from logD, which is pH-dependent and accounts for the distribution of all ionization states.

Typical logP values for organic molecules span roughly -2 to 6; values beyond this range are uncommon and may indicate measurement or methodological issues. LogP is a simplified descriptor and should be interpreted alongside other properties such as logS (solubility) and logP-dependent pharmacokinetic parameters.