PNNL

Abstract

Redox reactions are ubiquitous in organic synthesis and intrinsic to organic electrosynthesis. Nonetheless, the language and concepts used to describe reactions in these two domains are sufficiently different to create barriers that hinder broader adoption and understanding of electrochemical methods. Here, we survey fundamental principles underlying chemical and electrochemical redox reactions, including free energy, reaction driving force, voltage, and overpotential, in an effort to bridge some of the common gaps. Redox potentials observed in electrochemical experiments with organic molecules are very different from the thermodynamic potentials of synthetic organic redox reactions, and the differences between these values are explained. Standard potentials (?E°) are compared to the corresponding free energies (?G°) of organic redox reactions in an effort to demystify the meaning of "voltage" and explain why redox potentials for reactions involving different numbers of electrons can follow non-intuitive trends. Finally, the concept of "overpotential" is discussed in the context of chemical and electrochemical redox reactions, and it is shown to provide the basis for chemoselectivity and functional group compatibility in synthetic organic reactions. It is hoped that this discussion will increase the accessibility of electrochemistry for individuals who have not received formal training in this area.