Fenton's reagent

Fenton's reagent is a solution of hydrogen peroxide and an iron catalyst that is used to oxidize contaminants or waste waters. Fenton's reagent can be used to destroy organic compounds such as trichloroethylene (TCE) and tetrachloroethylene (PCE).

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It was developed in the 1890s by Henry John Horstman Fenton.

Ferrous Iron(II) is oxidized by hydrogen peroxide to ferric iron(III), a hydroxyl radical and a hydroxyl anion. Iron(III) is then reduced back to iron(II), a peroxide radical and a proton by the same hydrogen peroxide (disproportionation).

(1) Fe²⁺ + H₂O₂ → Fe³⁺ + OH· + OH⁻

(2) Fe³⁺ + H₂O₂ → Fe²⁺ + OOH· + H⁺

In the net reaction the presence of iron is truly catalytic and two molecules of hydrogen peroxide are converted into two hydroxyl radicals and water. The generated radicals then engage in secondary reactions. Iron(II) sulfate is a typical iron compound in Fenton's reagent.

Fenton's reagent is used in organic synthesis for the hydroxylation of arenes in a radical substitution reaction such as the classical conversion of benzene into phenol.

(3) C₆H₆ + FeSO₄ + H₂O₂ → C₆H₅OH

A recent hydroxylation example involves the oxidation of barbituric acid to alloxane ^[1]. 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.

The mismanagement of iron in cellular systems can lead to the toxic accumulation of iron in organ systems such as the liver and brain. It is believed that this build up of iron eventually leads to the production of free radicals leading to oxidative stress, cellular damage and eventual cellular death via apoptotic signaling.

References

• ^  Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers H. J. Brömme, W. Mörke and E. Peschke Journal of Pineal Research Volume 33 Issue 4 Page 239 - November 2002 PubMed Abstract
• Sara Goldstein, Dan Meyerstein and Gidon Czapski (1993). "The Fenton reagents". Free Radical Biology and Medicine 15 (4): 435-445. doi:10.1016/0891-5849(93)90043-T.
• H. J. H. Fenton (1894). "Oxidation of tartaric acid in presence of iron". J. Chem. Soc., Trans. (65): 899-911. doi:10.1039/CT8946500899.