Parametrization of lipophilic properties of some aromaticaliphatic acids in paper chromatography

The relationship between hydrophobicity and R^M has been studied for four series of acids, namely arylacetic, cinnamic, β-arylisobutyric, and α-methylcinnamic. The possibility of using pK values or polar constants to correct for dissociation of the acids investigated is discussed. The influence of substituent alkoxy groups on the relationship was investigated, and it was found that polar constants were important, even in systems in which dissociation was inhibited by addition of formic acid. In these circumstances, the polar constants probably compensate for modification of the hydrogen ion donor-acceptor properties of alkoxy derivatives. This phenomenon evidently plays a decisive role in those chromatographic systems markedly different from the reference partition system n-octanol-water.