Prediction of the lipophilicity of some N-hydroxyethylamides of aryloxyalkylene and pyridine carboxylic acids by reversed-phase thin-layer chromatography

The lipophilicity of nine compounds, the N-hydroxyethylamides of some arylo xyalkylene and pyridine carboxylic acids, compounds with biological activit y against Lepidium sativum, has been studied by reversed-phase high-perform ance thin-layer chromatography (RPHPTLC) on octyl silica plates with methan ol-water as mobile phase. R-Mw values, a measure of compound lipophilicity, were obtained by extrapolation to 100% water as mobile phase. Partition co efficients between l-octanol and water, logP, were calculated by use of Rek ker's revised fragmental constant system or obtained from Pomona College da tabase. Linear correlations were obtained between R-Mw values and calculate d logP values. A goad linear correlation (r > 0.99) was obtained between ex trapolated R-Mw values and the slope, a(1), of the linear relationships R-M = f(phi), where phi is the concentration of methanol in the mobile phase, showing that the compounds behave similarly in this specific system. These relationships can be used for prediction of the lipophilicity of similar co mpounds from the same structural group.