Hydroperoxyl
| Hydroperoxyl | |
|---|---|
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Hydroperoxyl |
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Dioxidanyl |
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Other names
Peroxyl radical |
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| Identifiers | |
| CAS number | 3170-83-0  |
| PubChem | 520535 |
| ChemSpider | 454055 |
| ChEBI | CHEBI:25935 |
| Gmelin Reference | 506 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | HO2 |
| Molar mass | 33.01 g mol−1 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
The hydroperoxyl radical, also known as the perhydroxyl radical, is the protonated form of superoxide with the chemical formula HO2.
Formation
Hydroperoxyl is formed through the transfer of a proton to an oxygen atom.[1]
Reactivity
The superoxide anion, O2−, and the hydroperoxyl radical are in equilibrium in aqueous solution:
- O2− + H2O
HO2 + OH−
HO2 + OH−The protonation/deprotonation equilibrium exhibits a pKa of 4.88;[2] 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.
Effect on environment
Hydroperoxyl is responsible for the destruction of ozone in the stratosphere, and it is formed as a result of the oxidation of hydrocarbons in the troposphere.[1]
References
- ^ a b "Hydroperoxyl radical". Glossary of Meteorology.
- ^ Reactivity of HO2/O2− Radicals in Aqueous Solution. J Phys Chem Ref Data, 1985. 14(4): p. 1041-1091
