| Abstract: | Two acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6-di-O-n-pentyl-3-O-trifluoroacetyl)- γ-cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2- and 3-hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four-carbon chain attached to the stereogenic center. For longer-chain fluoroacyl derivative groups stereoselectivity was higher for the 2- and 3-hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl-branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole–dipole contribution and some form of steric component, depending upon the shape and/or size of the solute. |
