Effect of β-cyclodextrin on intra and intermolecular Michael addition of some catechol derivatives

The oxidation reactions of catechol, dopamine and epinephrine have been studied in the absence and presence of N-methylaniline by UV-Vis. Spectrophotometry. A variety of reaction pathways (inter and intramolecular reactions) that followed by this oxidation have been observed depending on the nature of catechol derivatives. The observed homogeneous rate constants of the reactions were estimated by fitting the absorption time profiles for each reaction. The effect of beta-cyclodextrin and its inclusion complex has also been studied on the chosen reactions. The formation constants of the complexes of catechol, dopamine and epinephrine with beta-cyclodextrin as well as the rate constants of the reactions of free and complexed forms have been obtained by fitting the absorption-time spectra to a proposed kinetic-equilibrium model. (C) 2013 Elsevier BM. All rights reserved.