alpha- and beta-cyclodextrin complexes n-alkyl carboxylic acids and n-alkyl p-hydroxy benzoates. A molecular mechanics study of 1 : 1 and 1 : 2 associations

Molecular mechanics (MM) methods were employed to evaluate stabilization upon formation of inclusion compounds between two different guest molecules and alpha- and beta-cyclodextrins (CDs) for two different stoichiometries 1: 1 and 1:2. The two guest molecules studied were n-alkyl carboxylic acids and n-alkyl p-hydroxy benzoates with variety of chain lengths. The computed stability for the inclusion compounds between alpha-CDs and n-alkyl carboxylic acids reproduced experimental data reported in the literature. The transition between 1:1/1:2 complexes occurred at an alkyl chain length of n(C) = 9. It was previously demonstrated by diffusion coefficients measures that a stable 1:2 stoichiometry inclusion compound could be formed between n-alkyl p-hydroxy benzoates and alpha-CD for the chain length n(C) > 4. The computed results reproduced the experimental ones. The combination between OPLS and GB/SA resulted in better agreements with experiments than those obtained, with MM2 and MM3. (C) 2002 Elsevier Science B.V. All rights reserved.594320721