Fenton's reagent
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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).
It was developed in the 1890s by H.J.H. Fenton.
Ferrous Iron(II) is oxidized to ferric iron(III) by hydrogen peroxide to a hydroxyl radical and a hydroxyl anion. Iron(III) is then reduced back to iron(II) by the same hydrogen peroxide (disproportionation) to a peroxide radical and a proton.
(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 [#endnote_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 Rx that Fenton utilizes can be seen in nature by the facilitation of free-radical oxidation in the cytoplasm and nucleus of living cells, where iron ions are present. Cellular oxidative damage remains a leading hypothesis of aging processes.
External links
- [USGS definition]
- Dimerization of tert-butanol in Organic Syntheses [Online article]
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]
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