Фентон реагенты: тотығу процесі және қолданылуы

Strongly oxidizing solution of hydrogen peroxide mixed with dissolved iron as catalyst

Fenton's reagent is a solution of hydrogen peroxide (H2O2) and an iron catalyst (typically iron(II) sulfate, FeSO4). It is used to oxidize contaminants or waste water as part of an advanced oxidation process. Fenton's reagent can be used to destroy organic compounds such as trichloroethylene and tetrachloroethylene (perchloroethylene). It was developed in the 1890s by Henry John Horstman Fenton as an analytical reagent.

Iron(II) is oxidized by hydrogen peroxide to iron(III), forming a hydroxyl radical and a hydroxide ion in the process. Iron(III) is then reduced back to iron(II) by another molecule of hydrogen peroxide, forming a hydroperoxyl radical and a proton. The net effect is a disproportionation of hydrogen peroxide to create two different oxygen radical species, with water (H+ + OH−) as a byproduct. The free radicals generated by this process engage in secondary reactions. For example, the hydroxyl is a powerful, non selective oxidant. Oxidation of an organic compound by Fenton's reagent is rapid and exothermic and results in the oxidation of contaminants to primarily carbon dioxide and water. Reaction was suggested by Haber and Weiss in the 1930s as part of what would become the Haber–Weiss reaction. Iron(II) sulfate is typically used as the iron catalyst. The exact mechanisms of the redox cycle are uncertain, and non OH• oxidizing mechanisms of organic compounds have also been suggested. Therefore, it may be appropriate to broadly discuss Fenton chemistry rather than a specific Fenton reaction. In the electro Fenton process, hydrogen peroxide is produced in situ from the electrochemical reduction of oxygen. Fenton's reagent is also used in organic synthesis for the hydroxylation of arenes in a radical substitution reaction such as the classical conversion of benzene into phenol. An example hydroxylation reaction involves the oxidation of barbituric acid to alloxane. Another application of the reagent in organic synthesis is in coupling reactions of alkanes. As an example tert butanol is dimerized with Fenton's reagent and sulfuric acid to 2,5 dimethyl 2,5 hexanediol. Fenton's reagent is also widely used in the field of environmental science for water purification and soil remediation. Various hazardous wastewater were reported to be effectively degraded through Fenton's reagent.

The Fenton reaction has different implications in biology because it involves the formation of free radicals by chemical species naturally present in the cell under in vivo conditions. Transition metal ions such as iron and copper can donate or accept free electrons via intracellular reactions and so contribute to the formation, or at the contrary to the scavenging, of free radicals. Superoxide ions and transition metals act in a synergistic way in the appearance of free radical damages. Therefore, although the clinical significance is still unclear, it is one of the viable reasons to avoid iron supplementation in patients with active infections, whereas other reasons include iron mediated infections.

Mixtures of |Fe2+ and |H2O2 are called Fenton reagent. If |Fe2+ is replaced by |Fe3+, it is called Fenton like reagent. Numerous transition metal ions and their complexes in their lower oxidation states (|LmMn+) were found to have the oxidative features of the Fenton reagent, and, therefore, the mixtures of these metal compounds with |H2O2 were named "Fenton like" reagents.