Octanol/water partition coefficient of ortho‐substituted aromatic solutes

The partition coefficient (P) of some mono‐ and di‐ortho‐substituted aromatic compounds was measured in a 1‐octanol/water system. For each series of compounds with the same functional group, the π value (the difference in the log P value between the substituted and unsubstituted compound) was analyzed on the same basis as the values of meta‐ and para‐substituted isomers by an extended Hammett‐Taft procedure. In the procedure, we considered the intramolecular electronic and steric effects, operating between substituents and governing the relative hydrogen‐bonding solvation with partitioning solvents for solutes in which internal hydrogen‐bond formation can be ignored. The π value for mono‐ and di‐ortho‐substituted derivatives was adequately included in the correlation equation for the values of the meta‐ and para‐substituted derivatives in each series. The effect of di‐ortho substituents on partition behaviors could be roughly expressed by the sum of the effects of the 2‐ and 6‐position substituents.