Hydroperoxyl
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Names | |
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Preferred IUPAC name
Hydroperoxyl | |
Systematic IUPAC name
Dioxidanyl | |
Other names
Peroxyl radical, hydrogen superoxide, hydrogen dioxide
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Identifiers | |
3D model (
JSmol ) |
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ChEBI | |
ChemSpider | |
506 | |
PubChem CID
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CompTox Dashboard (EPA)
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Properties | |
HO2 | |
Molar mass | 33.006 g·mol−1 |
Acidity (pKa) | 4.88[1] |
Basicity (pKb) | 9.12 (basicity of superoxide ion) |
Conjugate base
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Superoxide anion
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The hydroperoxyl
Structure and reactions
The molecule has a bent structure.[3]
The superoxide anion, O−
2, and the hydroperoxyl radical exist in equilibrium in aqueous solution:
- O−
2 + H2O ⇌ HO2 + OH−
The pKa of HO2 is 4.88. Therefore, about 0.3% of any superoxide present in the cytosol of a typical cell is in the protonated form.[4]
It oxidizes nitric oxide to nitrogen dioxide:[2]
- NO + HO2 → NO2 + HO
Reactive oxygen species in biology
Together with its
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.[5]
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.
References
- doi:10.1063/1.555739.
- ^ PMID 14664647.
- .
- PMID 12042065.
- ^ "Hydroperoxyl radical". Glossary of Meteorology. American Meteorological Society. 25 April 2012. Retrieved 22 August 2013.