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}} The hydroperoxyl radical, also known as the perhydroxyl radical, is the protonated form of superoxide with the chemical formula HO2.


Hydroperoxyl is formed through the transfer of a hydrogen atom or even ion(s) to molecular oxygen, an oxygen atom to a hydroxyl radical or a proton to a superoxide anion.


The superoxide anion, O2−, and the hydroperoxyl radical are in equilibrium in aqueous solution: O2− + H2O HO2 + OH− The protonation/deprotonation equilibrium exhibits a pKa of 4.88; consequently, about 0.3% of any superoxide present in the cytosol of a typical cell is in the protonated form. Unlike O2−, which predominantly acts as a reductant, HO2 can act as an oxidant in a number of biologically important reactions, such as the abstraction of hydrogen atoms from tocopherol and polyunstaturated fatty acids in the lipid bilayer. As such, it may be an important initiator of lipid peroxidation. Because dielectric constant has a strong effect on pKa, and the dielectric constant of air is quite low, superoxide produced (photochemically) in the atmosphere is almost exclusively present as HO2. As HO2 is quite reactive, it acts as a "cleanser" of the atmosphere by degrading certain organic pollutants. As such, the chemistry of HO2 is of considerable geochemical importance.

Importance for atmospheric chemistry

Gaseous hydroperoxyl is involved in reaction cycles that destroy stratospheric ozone. It is also present in the troposphere, where it is essentially a byproduct of the oxidation of carbon monoxide and of hydrocarbons by the hydroxyl radical.


"green air" © 2007 - Ingo Malchow, Webdesign Neustrelitz
This article based upon the http://en.wikipedia.org/wiki/Hydroperoxyl, the free encyclopaedia Wikipedia and is licensed under the GNU Free Documentation License.
Further informations available on the list of authors and history: http://en.wikipedia.org/w/index.php?title=Hydroperoxyl&action=history
presented by: Ingo Malchow, Mirower Bogen 22, 17235 Neustrelitz, Germany