Retention Studies of Alkyl- and Halogen-Substituted Aromatics On Normal-Phase Silica and Alumina Columns. III. Methylbenzenes, Methylnaphthalenes, Methylbiphenyls, and a Selection of Poly-Aromatics

Retention data of methylbenzenes, methylnaphthalenes and methylbiphenyls determined on normal-phase silica and alumina columns are submitted to mutual comparison. Binding of all three classes of compounds to the adsorbents seems exclusively located in the pi-cloud of their aromatic systems. Conclusive evidence can be obtained from retention experiments on a selection of poly-aromatic hydrocarbons with varying pi-patterns. Additional information to this view is obtainable from UV-spectral literature - data. A set of pictures visualizes our views on the adsorption of the investigated aromatics both to silica and to alumina.