A Model for Characterization of Successive Hydrogen Bonding Interactions with Electrochemically Generated Charged Species. The Quinone Electroreduction in the Presence of Donor Protons

In this work, it is considered that charged molecules, such as the semiquinone (Q^.?) and the benzoquinone dianion (Q^2?), interact with weak donor protons (DH) via hydrogen bonding through consecutive association steps which depend on the concentration of DH. On the basis of a reversible voltammetric behavior, a model is presented for determining integer numbers of associated molecules of DH and the thermodynamic constants (β_i) related with each association equilibrium. The electrochemical reduction of 1,4‐benzoquinone (Q) in the presence of different aliphatic alcohols and diols, in dimethylsulfoxide (DMSO), illustrates the utility of the model. Based on analysis of half‐wave potential variation according to the DH concentration, the association constants were determined for the Q^.? and Q^2? complexes with the different alcohols studied and mole‐fraction distribution diagrams were constructed. These diagrams explain the fractional values, produced using the typical model, widely reported in the literature, for study the hydrogen bonding between the electrochemically generated charged species with donor protons.