H-1-nuclear magnetic resonance and phase solubility studies of the stoichiometries in 2,4-D: alpha- and beta-cyclodextrins inclusion complexes

The interaction in solution between 2,4-dichlorophenoxyacetic acid with alp ha- and beta-cyclodextrins was evaluated by phase solubility studies. Assoc iation constants were calculated by this technique. The stoichiometries wer e 1 : 2 and 1 : 1 for the alpha- and beta-cyclodextrin complexes, respectiv ely. In order to corroborate the complexation and the knowledge of structur al aspects of the host : guest interaction, proton nuclear magnetic resonan ce (H-1-NMR) spectroscopy was employed. The application of the continuous v ariation technique corroborated the calculated complex stoichiometries by s olubility assays. Complementary NOE studies were applied in order to corrob orate the proposed complex structures.