Comparative chromatographic adsorbabilities of some azines, thioles and thienopyridines, their heteroatom oxides and other derivatives on silica gel

Thin layer chromatographic Rf data on silica gel are reported for 64 compounds containing either a thiole sulfur atom, one or more azine nitrogen atoms, or both. Thiole adsorbates are compared with 28 aromatic hydrocarbons and non‐heterocyclic sulfur compounds. In general the orders of Rf values found are thioles > sulfides > sulfones > sulfoxides > azine N‐oxides and azines > azine‐N‐oxides. Results are interpreted in terms of hydrogen bonding from the silica gel to the adsorbate. The different orders of adsorbability found amongst four series of condensed thiophenes and their arene analogs for chromatography on silica gel and on alumina are rationalized in terms of planarity and acid‐base interactions. Correlations of the tlc data with separations on columns are presented.