[The relationship between thin-layer chromatographic retention values and molecular structures of phenol and aniline...

The Rf values of 24 phenol and aniline derivatives were determined on silica gel layer with three solvent mixtures of hexane-ethyl acetate in different proportions as the mobile phases. The compounds were divided into two species having different features by using the oblique factor analysis. It was found that in the first species there is no methyl group on their benzene rings and in the second all have methyl group in their benzene rings, which results in higher Rf values of the latter than those of the former. It was also found that the sequence of the groups on the benzene rings which make the Rf values of the compounds higher was --CH3 >--OH >--NH2 and the compounds having the ortho-substituted groups give the higher Rf values than para- and meta-substituted ones due to the formation of hydrogen bond within their molecules. The multi-parameter regression analyses of Rf values with the topological indexes degree B and M for the two species showed rather good correlation between the TLC retention values and the molecular structure of the compounds. The findings are of great practical significance.