Hansch constant

https://doi.org/10.1351/goldbook.H02736
A measure of the capability of a solute for @[email protected] @[email protected] interaction based on the @[email protected] \(P\) for distribution of the solute between octan-1-ol and water. The most general way of applying \(P\) in @[email protected], @[email protected], etc. is as log \(P\), but the behaviour of substituted benzene derivatives may be quantified by a substituent constant scale, \(\pi \), which is defined in a way analogous to the Hammett σ scale. There are various scales, depending on the substrate series used as reference.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1119 [Terms] [Paper]