Hydroxyl radicals
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| Names | |
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IUPAC name
Hydroxyl radical
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Systematic IUPAC name
Oxidanyl (substitutive)
Hydridooxygen(•) (additive) |
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| Other names
Hydroxy
Hydroxyl |
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| Identifiers | |
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3D model (Jmol)
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| ChEBI | |
| ChemSpider | |
| 105 | |
| KEGG | |
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PubChem CID
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| Properties | |
| HO | |
| Molar mass | 17.01 g·mol−1 |
| Thermochemistry | |
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Std molar
entropy (S |
183.71 J K−1 mol−1 |
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Std enthalpy of
formation (ΔfH |
38.99 kJ mol−1 |
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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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| Infobox references | |
Hydroxyl
The hydroxyl radical, •OH, is the neutral form of the hydroxide ion (OH−). Hydroxyl radicals are highly reactive (easily becoming hydroxyl groups) and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides (ROOH) or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. It is also an important radical formed in radiation chemistry, since it leads to the formation of hydrogen peroxide and oxygen, which can enhance corrosion and SCC in coolant systems subjected to radioactive environments. Hydroxyl radicals are also produced during UV-light dissociation of H2O2 (suggested in 1879) and likely in Fenton chemistry, where trace amounts of reduced transition metals catalyze peroxide-mediated oxidations of organic compounds.
In organic synthesis, hydroxyl radicals are most commonly generated by photolysis of 1-hydroxy-2(1H)-pyridinethione.
The hydroxyl radical is often referred to as the "detergent" of the troposphere because it reacts with many pollutants, decomposing them through "cracking", often acting as the first step to their removal. It also has an important role in eliminating some greenhouse gases like methane and ozone. The rate of reaction with the hydroxyl radical often determines how long many pollutants last in the atmosphere, if they do not undergo photolysis or are rained out. For instance methane, which reacts relatively slowly with hydroxyl radical, has an average lifetime of >5 years and many CFCs have lifetimes of 50 years or more. Pollutants, such as larger hydrocarbons, can have very short average lifetimes of less than a few hours.
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Wikipedia