Structure and Dynamics of Host/Guest Complexation at the Liquid/Liquid Interface: Implications for Inverse Phase Transfer Catalysis

beta-Cyclodextrin (beta-CD) enhances the rate of the biphasic S(N)2 reaction between 1-bromooctane and anionic nucleophiles in an adjacent, immiscible aqueous phase. In this work, molecular dynamics-simulations were used to study the mass-transfer component of this inverse phase transfer catalysis system. The orientation of the solvent molecules around the beta-CD molecule was investigated in detail, revealing the preferred position of the 1-bromooctane guest within the, beta-CD host molecule. Potentials of mean force for the insertion/extraction of the guest molecule were calculated in the two bulk solvents and at the liquid/liquid interface. The findings of these orientational and energetic studies suggest a logical exchange mechanism facilitated by beta-CD.