Studies in the relationship between molecular structure and chromatographic behaviour-I: Behaviour of some nitrophenols chromatographed on alumina-impregnated surfaces

Abstract A series of nuclear-substituted nitrophenols has been chromatographed on various papers (cellulose, alumina-impregnated cellulose and alumina-impregnated glass fibre), using a simple nonpolar developing solvent (anhydrous cyclohexane). From a consideration of the R f values obtained, it is suggested that these compounds are mainly chromatographed by an adsorption process. As a first approximation the mechanism postulated is one of intennolecular hydrogen bonding between the nitro, phenolic and/or halogen groups of the molecule and the hydroxyl groups considered to cover the impregnation. This bonding is modified by the intramolecular hydrogen bonding of the nuclear substituents. The significance of electronic and steric effects is considered. It is suggested that because of the ease of delocalisation of electronic effects in these nuclear systems, no group or atomic Chromatographie parameters can be assigned.