David Woodcock

Relationships between hansch's л parameters and RM values determined on polyamide thin layers

Abstract R M values of two groups of N-(1-substituted-2,2,2-trichloroethyl) formamides have been measured using chromatography on polyamide thin layers. Substituent △ R M values correlated poorly with Hanschs л parameters, unless the electronic effect of the substituent was taken into account. R M values correlated with a linear combination of л and certain electronic parameters, including the Hammett σ function and specific quantum mechanical indices. Consequently, the relative influence of electronically determined solvation forces is though to be different in polyamide TLC from that in Hanschs octanol-water partitioning system, and in Hansch-type regression equations employing parameters determined on polyamide layers some fraction of the electronic term will compensate for this effect. The mechanism of chromatography on polyamide thin layers is considered, and the possibility raised that, with certain compounds, charge-transfer complexing might be an important influence.