| 词条 | Fenton's reagent |
| 释义 |
OverviewIron(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 ({{math|size=100%|H+ + OH−}}) as a byproduct. {{NumBlk|:| Fe2+ + H2O2 → Fe3+ + HO• + OH−|{{EquationRef|1}}}}{{NumBlk|:| Fe3+ + H2O2 → Fe2+ + HOO• + H+|{{EquationRef|2}}}}The free radicals generated by this process then 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.[3] Reaction ({{EquationNote|1}}) was suggested by Haber and Weiss in the 1930s as part of what would become the Haber–Weiss reaction.[4] 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.{{citation needed|date=October 2013}} 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.[5] 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. {{NumBlk|:| C6H6 + FeSO4 + H2O2 → C6H5OH|{{EquationRef|3}}}}A recent hydroxylation example involves the oxidation of barbituric acid to alloxane.[6] 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.[7] Biomedical applicationsThe Fenton reaction has importance in biology because it involves the creation of free radicals by chemicals that are present in vivo. Transition-metal ions such as iron and copper donate or accept free electrons via intracellular reactions and help in creating free radicals. Most intracellular iron is in ferric (+3 ion) form and must be reduced to the ferrous (+2) form to take part in Fenton reaction. Superoxide ions and transition metals act in a synergistic manner in the creation of free radical damage.[8] Therefore, although the clinical significance is still unclear, it is one of the viable reason to avoid iron supplementation in patients with active infections, whereas other reasons include iron-mediated infections.[9] See also
References1. ^{{cite journal | doi = 10.1039/ct8946500899 | title = Oxidation of tartaric acid in presence of iron | author = Fenton H.J.H. | journal = J. Chem. Soc., Trans. | volume = 65 | issue = 65 | pages = 899–911 | year = 1894 | url = https://books.google.com/books?id=Deo2AAAAYAAJ&pg=PA899#v=onepage&q&f=false }} 2. ^ Hayyan M., Hashim M.A., AlNashef I.M., Superoxide Ion: Generation and Chemical Implications, Chem. Rev., 2016, 116 (5), pp 3029–3085. 10.1021/acs.chemrev.5b00407] 3. ^{{Cite web | url=http://geocleanse.com/fentonsreagent.asp | title=Geo-Cleanse International, INC. | REAGENTS}} 4. ^{{cite journal |author1=Haber, F. |author2=Weiss, J. | year = 1932 | title = Über die Katalyse des Hydroperoxydes | journal = Naturwissenschaften | doi = 10.1007/BF0150471|volume = 20|issue = 51|pages = 948–950|doi-broken-date=2019-03-16 }} 5. ^{{cite journal |author1=Juan Casado |author2=Jordi Fornaguera |author3=Maria I. Galan |title=Mineralization of Aromatics in Water by Sunlight-Assisted Electro-Fenton Technology in a Pilot Reactor |journal=Environ. Sci. Technol. |volume=39 |issue=6 |pages=1843–47 |date=January 2005 |pmid= 15819245|doi= 10.1021/es0498787|url=http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2005/39/i06/abs/es0498787.html|bibcode=2005EnST...39.1843C}} 6. ^{{cite journal |vauthors=Brömme HJ, Mörke W, Peschke E |title=Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers |journal=J. Pineal Res. |volume=33 |issue=4 |pages=239–47 |date=November 2002 |pmid=12390507 |doi= 10.1034/j.1600-079X.2002.02936.x}} 7. ^{{OrgSynth | collvol = 5 | collvolpages = 1026 | prep = cv5p1026 | title = α,α,α',α'-Tetramethyltetramethylene glycol | author = E. L. Jenner | year = 1973}} 8. ^{{cite book|author=Robbins|author2=Cotran|last-author-amp=yes|title=Pathologic Basis of Disease|edition=7th|year=2008|publisher=Elsevier|isbn=9780808923022|pages=16}} 9. ^{{Cite journal|last=Lapointe|first=Marc|date=2004-01-01|title=Iron supplementation in the intensive care unit: when, how much, and by what route?|journal=Critical Care|volume=8|issue=2|pages=S37–41|doi=10.1186/cc2825|issn=1364-8535|pmc=3226152|pmid=15196322}} Further reading
| title = The Fenton reagents |author1=Goldstein Sara |author2=Meyerstein Dan |author3=Czapski Gidon | journal = Free Radical Biology and Medicine | volume = 15 | issue = 4 | pages = 435–445 | year = 1993 | doi = 10.1016/0891-5849(93)90043-T | pmid = 8225025 }}
External links
4 : Oxidizing agents|Environmental chemistry|Analytical reagents|Free radicals |
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