Entoxidation

Entoxidation is a proposed class of oxidation reactions in which the oxidative event originates from within a molecule rather than from an external oxidant. The term is not widely adopted in standard chemical nomenclature and is often used in theoretical or speculative discussions of reaction design and enzymatic mechanisms. In entoxidation, internal activation mechanisms—such as the formation of radical or ionic intermediates within the substrate, intramolecular electron transfer, or redox-active cofactors that generate an internal oxidizing equivalent—initiate subsequent oxidative steps that modify specific bonds or functional groups.

Mechanistically, entoxidation can involve generation of substrate-centered radical cations, intramolecular hydrogen-atom migrations, or rearrangements that relocate oxygen or oxidizing equivalents to targeted sites. In biological systems, enzymes may create internal oxidants via cofactors (for example metalloenzymes or radical-transfer enzymes) that trigger oxidation from within the substrate, while in chemical synthesis, photocatalytic or electrochemical strategies aim to generate internal oxidants in situ. These processes differ from classical oxidation by external oxidants, and also differ from autoxidation, where ambient oxygen or moisture reacts with substrates.

The term remains debated, and some researchers prefer describing these reactions as intramolecular or internally initiated oxidations. Potential advantages include enhanced site selectivity and reduced reliance on highly reactive external oxidants, though practical control of selectivity and reaction outcome remains challenging. Current investigations focus on identifying characteristic intermediates, developing analytical tools, and creating models to predict when internal activation can drive productive oxidation.

See also: oxidation, intramolecular reactions, radical chemistry, enzymatic oxidation, autoxidation.