Resumen de Determination of Lipophilicity Constants of Sulfonamide Substituents
Maria Auxiliadôra Fontes Prado
This article describes a simple laboratory activity using reversed-phase thin-layer chromatography (a stationary nonpolar phase and a mobile polar phase). The Rf values determined for sulfonamides by means of reversed-phase thin-layer chromatography are used to calculate the chromatographic parameter Rm and the lipophilicity constants (π) of different substituent groups of sulfonamides. The partition coefficients (P) of sulfonamides can be calculated using the π constants and partition coefficients of sulfanilamides. This experiment offers an opportunity to demonstrate the differences between straight and reversed-phase thin-layer chromatography and introduces the chromatographic parameter Rm. It also shows how chromatography can be used to determine a very important physicochemical parameter, the partition coefficient, which is used in quantitative structure-activity relationship studies of drugs. The experiment is suitable for classes of up to about 20 students.
