Hydrogen bonding effects on the association processes between chloranil and a series of amides

In this work, a series of amides has been studied as hydrogen bonding stabilising species of the reduction intermediates of a weakly basic quinone such as chloranil. The amide structure was selected in order to evaluate the role of a single or three centered intramolecular hydrogen bond on the intermolecular hydrogen bonding interaction with the quinone reduction products. The association process between the semiquinone and the amides is not important. However, the dianion is associated according to different thermodynamic and kinetic conditions. The voltammetric behaviour of these systems was studied by simulation of two consecutive electron transfer steps with two successive association processes coupled to the dianion. The first association process presents a wide range of equilibrium constant values. According to the amide structure, the interference of the electron transfer kinetics on the association processes, was established to be increased with the extent of the interaction, which is explained by considering the acidity of the hydrogen donor groups in the amide and the participation of two intermolecular hydrogen bonds.