SOLUTE SOLVENT INTERACTIONS BETWEEN CYCLODEXTRIN AND WATER - A MOLECULAR MECHANICAL STUDY

Monte Carlo simulations have been carried out for systems including alpha- and beta-cyclodextrin (alpha- and beta-CD) and water. The possibility of obtaining information about entropic and enthalpic contributions to solution reactions via Monte Carlo calculations has been demonstrated, using TIPS functions for nonbonded interactions of the CDs and the TIP3P model for water. The molecular mechanical calculations performed are in accordance with previous experimental and computational findings. A description of solvation behavior has been given using a combined approach of nonequilibrium (energetic minimization) and equilibrium (Monte Carlo) simulations. The solid-state hydration characteristics were described by minimization calculations, whereas the liquid-state solvation reaction could be interpreted by Monte Carlo calculations. The decreased solubility of beta-CD in water appears to be due to the marked structure of water arising from water-beta-CD interactions, causing a compensation of the favorable enthalpy by the unfavorable entropy of solution.