High-performance liquid chromatography of alkylbenzenes : Relationship with lipophilicities as determined from octanol-water partition coefficients or calculated from hydrophobic fragmental data and connectivity indices; lipophilicity predictions for polyaromatics

Abstract

High-performance liquid chromatography (HPLC) was used to study the relationships between the retention and hydrophobicity of a series of alkylbenzenes. One of the aims was a critical comparison of the use of the logarithms of experimentally determined partition coefficients (log P) (octanol—water system), calculated log P (applying the Rekker fragment system), calculated log P (applying the Leo-Hansch fragment system) or Kier's connectivity indices. The conclusions are that the Rekker system gives a good description (both relative and absolute) of HPLC hydrophobicities, that the Leo-Hansch system lacks absolute prediction in a number of instances and that the Kier indices can be regarded as reasonable substitutes in the description of the hydrophobicity of alkylbenzenes. Lipophilicities of polyaromatic structures can be calculated easily and with surprisingly high accuracy from Rekker's f constants.