Interaction of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with aza-18-crown-6 and aza-12-crown-4. Kinetic and spectrophotometric studies in chloroform and acetonitrile solutions

Abstract

Interactions of aza-18-crown-6 and aza-12-crown-4 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been examined spectrophotometrically in chloroform and acetonitrile solutions. The results indicate immediate formation of an electron donor–acceptor complex, DA [reaction (a)], which is followed by two relatively slow consecutive reactions (b). Pseudo-first-order rate constants at various temperatures for the formation of the ionic intermediate [D⁺A^–] and the final product have been evaluated by computer fitting of the absorbance–time data to appropriate equations. The formation constants of the resulting EDA complexes have also been determined. The influences of both the azacrowns’ structure and the solvent properties on the formation of EDA complexes and the rates of subsequent reactions are discussed.