Gas chromatographic separation of atropisomeric alkylated and polychlorinated biphenyls using modified cyclodextrins

Selectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2′ alkylated biphenyls. The configurational stability of 2,2′‐dimethyl and 2,2′‐diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2‐Isopropyl‐2′‐ t ‐butyl‐ and 2,2′‐di‐ t ‐butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2′‐diisopropyl‐ and 2,2′‐bis(trifluoromethyl)biphenyl show temperature‐dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.