Reoxidants

Reoxidants are chemical species that reoxidize a reduced species, regenerating the oxidized form necessary for ongoing redox processes. In many chemical and biochemical systems, reactions proceed through cycles in which a catalyst, mediator, or cofactor is reduced by substrate and must be reoxidized to continue functioning. A reagent performing this regeneration is called a reoxidant.

In catalysis, reoxidants restore the high-valent state of metal centers or redox mediators after electron transfer steps, enabling catalytic turnover. The choice of reoxidant influences selectivity, efficiency, and byproduct formation, and some systems use catalytic amounts with an external oxidant or electrochemical methods to sustain the cycle.

Common reoxidants include molecular oxygen in aerobic oxidation, hydrogen peroxide and organic peroxides, and inorganic oxidants such as permanganate, dichromate, periodate, and hypochlorite. In biochemistry and bioinspired chemistry, NAD+ and related cofactors act as terminal oxidants that reoxidize reduced cofactors. In electrochemical setups, an electrode serves as an electronic reoxidant, reestablishing the oxidized state without additional chemical reagents.

Important considerations when selecting a reoxidant include redox potential alignment with the reduced species, compatibility with substrates, reaction conditions, safety, cost, and environmental impact. Reoxidants are central to many oxidation processes, including synthetic organic transformations, energy storage systems, and metabolic pathways.