Enantioselective Binding in Gas Chromatography:a Computational Study of Chiral Selection Bypermethyl-?-Cyclodextrin

Stochastic molecular dynamics simulations were used to determine the enantiomer retention orders of moderately polar analytes binding to permethylated β-cyclodextrin, a popular chiral stationary phase used in gas chromatography. It is found that averaging over multiple trajectories, each of which are lengthy, is required to faithfully reproduce experiment. From the simulations we find the major binding domain to be the interior of the macrocycle rather than the exterior with most analytes having a preference for associating to the primary rim rather than to the secondary rim. It is also found that the intermolecular forces responsible for holding the complexes together are the short range dispersion forces, and that the enantiodifferentiating forces of the competing diastereomeric complexes are dominated by the van der Waals contributions to the intermolecular energy.