Difference between revisions of "Bromous acid"
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| − | '''Bromous acid''', HBrO<sub>2</sub>, is a purported [[oxoacid]] of [[bromine]]. Its existence as a molecular species has been considered doubtful | + | '''Bromous acid''', HBrO<sub>2</sub>, is a purported [[oxoacid]] of [[bromine]]. Its existence as a molecular species has been considered doubtful<ref name="Kirk-Othmer">{{Kirk-Othmer | first1 = S. D. | last1 = Ukeles | first2 = M. | last2 = Freiberg | contribution = Bromine, Inorganic Compounds | doi = 10.1002/0471238961.021815131001031 | year = 2002}}.</ref> but, although it is unstable with respect to [[disproportionation]], its lifetime in aqueous solution is sufficient for spectroscopic study.<ref name="pKa2"/><ref name="Ariese">{{citation | title = The disproportionation of bromous acid (HBrO<sub>2</sub>), key species of the Belousov-Zhabotinskii oscillating reaction | first1 = Freek | last1 = Ariese | first2 = Zsuzsanna | last2 = Ungvarai-Nagy | journal = J. Phys. Chem. | year = 1986 | volume = 90 | issue = 1 | pages = 1–4 | doi = 10.1021/j100273a001}}.</ref> It is an intermediate in the [[Belousov–Zhabotinskii reaction]].<ref name="Ariese"/> Some [[salt]]s ([[bromite]]s) are known.<ref name="Kirk-Othmer"/> |
| + | |||
| + | ==Disproportionation== | ||
| + | Bromous acid is unstable with respect to [[disproportionation]]: at acid pH, the thermodynamic products are [[bromine]] and [[bromate]]. | ||
| + | :5 HBrO<sub>2</sub> → Br<sub>2</sub> + 3 BrO{{su|b=3|p=−}} + 3 H<sup>+</sup> + H<sub>2</sub>O | ||
| + | The initial mechanism is simpler than that for [[chlorous acid]], as the production of [[bromine dioxide]] and the oxidation of [[water]] to [[oxygen]] are negligible. Hence, there are just two significant initial steps:<ref name="pKa2"/> | ||
| + | :HBrO<sub>2</sub> + HBrO<sub>2</sub> → HBrO + BrO{{su|b=3|p=−}} + H<sup>+</sup> ''k'' = 800(100) dm<sup>3</sup> mol<sup>−1</sup> s<sup>−1</sup> | ||
| + | :HBrO<sub>2</sub> + BrO{{su|b=2|p=−}} → HBrO + BrO{{su|b=3|p=−}} ''k'' = 39.1(26) dm<sup>3</sup> mol<sup>−1</sup> s<sup>−1</sup> | ||
==Notes and references== | ==Notes and references== | ||
Revision as of 09:34, 2 January 2011
| Bromous acid | |
|---|---|
| IUPAC name | Bromous acid[note 1] |
| Other names | Bromic(III) acid Hydroxy-λ3-bromanone Hydroxidooxidobromine |
| Identifiers | |
| InChI | InChI=1/BrHO2/c2-1-3/h(H,2,3) |
| InChIKey | DKSMCEUSSQTGBK-UHFFFAOYAC |
| Standard InChI | InChI=1S/BrHO2/c2-1-3/h(H,2,3) |
| Standard InChIKey | DKSMCEUSSQTGBK-UHFFFAOYSA-N |
| CAS number | [] |
| ChemSpider | |
| Properties[2][3] | |
| Chemical formula | HBrO2 |
| Molar mass | 112.91 g mol−1 |
| Acidity (pKa) | 3.46(12) |
| Related compounds | |
| Other halous acids | Chlorous acid |
| Other compounds | Hydrobromic acid Hypobromous acid Bromic acid Perbromic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Bromous acid, HBrO2, is a purported oxoacid of bromine. Its existence as a molecular species has been considered doubtful[4] but, although it is unstable with respect to disproportionation, its lifetime in aqueous solution is sufficient for spectroscopic study.[3][5] It is an intermediate in the Belousov–Zhabotinskii reaction.[5] Some salts (bromites) are known.[4]
Disproportionation
Bromous acid is unstable with respect to disproportionation: at acid pH, the thermodynamic products are bromine and bromate.
- 5 HBrO2 → Br2 + 3 BrO−3 + 3 H+ + H2O
The initial mechanism is simpler than that for chlorous acid, as the production of bromine dioxide and the oxidation of water to oxygen are negligible. Hence, there are just two significant initial steps:[3]
- HBrO2 + HBrO2 → HBrO + BrO−3 + H+ k = 800(100) dm3 mol−1 s−1
- HBrO2 + BrO−2 → HBrO + BrO−3 k = 39.1(26) dm3 mol−1 s−1
Notes and references
Notes
- ↑ Bromous acid is a retained name in IUPAC nomenclature.[1]
References
- ↑ Nomenclature of Inorganic Chemistry; IUPAC Recommendations 2005; Royal Society of Chemistry: Cambridge, 2005; p 287. ISBN 0-85404-438-8, <http://www.iupac.org/publications/books/rbook/Red_Book_2005.pdf>.
- ↑ Faria, Roberto de Barros; Epstein, Irving R.; Kustin, Kenneth Systematic design of chemical oscillators. Part 84. Determination of the pKa of bromous acid. J. Phys. Chem. 1992, 96 (17), 6861–63. DOI: 10.1021/j100196a003.
- ↑ 3.0 3.1 3.2 Faria, R. B.; Epstein, Irving R.; Kustin, Kenneth Kinetics of Disproportionation and pKa of Bromous Acid. J. Phys. Chem. 1994, 98 (4), 1363–67. DOI: 10.1021/j100055a051.
- ↑ 4.0 4.1 Ukeles, S. D.; Freiberg, M. Bromine, Inorganic Compounds. In Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley: New York, 2002. DOI: 10.1002/0471238961.021815131001031.
- ↑ 5.0 5.1 Ariese, Freek; Ungvarai-Nagy, Zsuzsanna The disproportionation of bromous acid (HBrO2), key species of the Belousov-Zhabotinskii oscillating reaction. J. Phys. Chem. 1986, 90 (1), 1–4. DOI: 10.1021/j100273a001.
External links
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See also the corresponding article on Wikipedia. |
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