Practice and theory of enantioselective complexation gas chromatography

Abstract

The practice and theory of enantioselective complexation GC is comprehensively reviewed for the first time. A multitude of racemic oxygen-, nitrogen- and sulfur-containing selectands can be separated without prior derivatization into enantiomers by complexation GC on optically active metal(II) bis[3-(perfluoroacyl)-(1R)-camphorate] selectors. Peak inversion is obtained when the selectors with opposite configuration are employed. Applications pertain to chiral analysis in asymmetric synthesis, enzymatic reactions, pheromone and flavour chemistry. Although the use of enantioselective complexation GC has diminished recently with the advent of modified cyclodextrins in enantioselective GC, the inherent principles of enantiorecognition together with other enantioselective phenomena can be elucidated easily by complexation GC. Using the concept of the retention-increment R′ which allows the distinction between non-enantioselective and enantioselective contributions to retention, concise thermodynamic parameters of enantioselectivity −ΔD,L(ΔG) are accessible. The enantiomerization of configurationally labile enantiomers can be investigated and quantified by complexation GC. Four distinct enantioselective processes and four different coalescence phenomena have been discerned in complexation GC.