Difference between revisions of "Bromous acid"
Physchim62 (talk | contribs) |
Physchim62 (talk | contribs) |
||
| Line 22: | Line 22: | ||
}} | }} | ||
}} | }} | ||
| − | '''Bromous acid''', HBrO<sub>2</sub>, is an [[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><ref>{{Cotton&Wilkinson5th|pages=566–67}}.</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"/> | + | '''Bromous acid''', HBrO<sub>2</sub>, is an [[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><ref>{{Cotton&Wilkinson5th|pages=566–67}}.</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"/><ref>{{citation | first1 = James C. | last1 = Sullivan | first2 = Richard C. | last2 = Thompson | title = Kinetic study of the cerium(IV)-bromous acid reaction in acid sulfate solution. Implications for the Belousov-Zhabotinskii oscillating reaction | journal = Inorg. Chem. | year = 1979 | volume = 18 | issue = 9 | pages = 2375–79 | doi = 10.1021/ic50199a009}}.</ref><ref>{{citation | first1 = F. | last1 = Hynne | first2 = P. | last2 = Graae Soerensen | first3 = H. | last3 = Neergaard | title = Oscillations of bromous acid, hypobromous acid, bromide, and cerium(4+) concentrations in the Belousov-Zhabotinskii reaction reconstructed from quenching experiments | journal = J. Phys. Chem. | year = 1991 | volume = 95 | issue = 3 | pages = 1315–18 | doi = 10.1021/j100156a052}}.</ref><ref>{{citation | first1 = Peter | last1 = Ruoff | first2 = Horst Dieter | last2 = Foersterling | first3 = Laszlo | last3 = Gyorgyi | first4 = Richard M. | last4 = Noyes | title = Bromous acid perturbations in the Belousov-Zhabotinskii reaction: experiments and model calculations of phase response curves | journal = J. Phys. Chem. | year = 1991 | volume = 95 | issue = 23 | pages = 9314–20 | doi = 10.1021/j100176a052}}. {{citation | first1 = Horst Dieter | last1 = Foersterling | first2 = Margit | last2 = Varga | title = Bromous acid/cerium(4+): reaction and HBrO<sub>2</sub> disproportionation measured in sulfuric acid solution at different acidities | journal = J. Phys. Chem. | year = 1993 | volume = 97 | issue = 30 | pages = 7932–38 | doi = 10.1021/j100132a022}}.</ref><ref>{{citation | first1 = Krisztina | last1 = Pelle | first2 = Maria | last2 = Wittmann | first3 = Klára | last3 = Lovrics | first4 = Zoltán | last4 = Noszticzius | first5 = Maria L. | last5 = Turco Liveri | first6 = Renato | last6 = Lombardo | title = Mechanistic Investigations of the BZ Reaction with Oxalic Acid Substrate. I. The Oscillatory Parameter Region and Rate Constants Measured for the Reactions of HOBr, HBrO<sub>2</sub>, and Acidic BrO<sub>3</sub><sup>−</sup> with Oxalic Acid | journal = J. Phys. Chem. A | year = 2004 | volume = 108 | issue = 25 | pages = 5377–85 | doi = 10.1021/jp048817s}}. {{citation | first1 = Lavinia | last1 = Onel | first2 = Gelu | last2 = Bourceanu | first3 = István | last3 = Bitter | first4 = Mária | last4 = Wittmann | first5 = Zoltán | last5 = Noszticzius | title = Uncatalyzed Reactions in the Classical Belousov−Zhabotinsky System. 2. The Malonic Acid−Bromate Reaction in Acidic Media | journal = J. Phys. Chem. A | year = 2006 | volume = 110 | issue = 3 | pages = 990–96 | doi = 10.1021/jp055259o}}.</ref> Some [[salt]]s ([[bromite]]s) are known.<ref name="Kirk-Othmer"/> |
==Disproportionation== | ==Disproportionation== | ||
| Line 62: | Line 62: | ||
===References=== | ===References=== | ||
| − | {{reflist}} | + | {{reflist|2}} |
==External links== | ==External links== | ||
Revision as of 10:36, 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) | 3.43(11) |
| 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 an oxoacid of bromine. Its existence as a molecular species has been considered doubtful[4][5] but, although it is unstable with respect to disproportionation, its lifetime in aqueous solution is sufficient for spectroscopic study.[3][6] It is an intermediate in the Belousov–Zhabotinskii reaction.[6][7][8][9][10] Some salts (bromites) are known.[4]
Contents
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
The hypobromous acid then disproportionates further to give the final products. There is no evidence of any catalysis of the disporportionation of HBrO2 by bromide ions (unlike the case of chlorous acid and chloride ions).[3]
Acidity
The acid dissociation constant of bromous acid can be calculated from the observed kinetics of its disproportionation:[3] Ka = 3.7(9) × 10−4 (pKa = 3.43). This is consistent with that which would be expected from periodic trends.
| pKa | ||
|---|---|---|
| HClO 7.47 |
HBrO 8.80 |
HIO 10.70 |
| HClO2 1.96 |
HBrO2 3.43 |
HIO2 — |
| HClO3 < 0 |
HBrO3 < 0 |
HIO3 0.80 |
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 3.3 3.4 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.
- ↑ Cotton, F. Albert; Wilkinson, Geoffrey Advanced Inorganic Chemistry, 5th ed.; Wiley-Interscience: New York, 1988; pp 566–67. ISBN 0-471-84997-9.
- ↑ 6.0 6.1 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.
- ↑ Sullivan, James C.; Thompson, Richard C. Kinetic study of the cerium(IV)-bromous acid reaction in acid sulfate solution. Implications for the Belousov-Zhabotinskii oscillating reaction. Inorg. Chem. 1979, 18 (9), 2375–79. DOI: 10.1021/ic50199a009.
- ↑ Hynne, F.; Graae Soerensen, P.; Neergaard, H. Oscillations of bromous acid, hypobromous acid, bromide, and cerium(4+) concentrations in the Belousov-Zhabotinskii reaction reconstructed from quenching experiments. J. Phys. Chem. 1991, 95 (3), 1315–18. DOI: 10.1021/j100156a052.
- ↑ Ruoff, Peter; Foersterling, Horst Dieter; Gyorgyi, Laszlo; Noyes, Richard M. Bromous acid perturbations in the Belousov-Zhabotinskii reaction: experiments and model calculations of phase response curves. J. Phys. Chem. 1991, 95 (23), 9314–20. DOI: 10.1021/j100176a052. Foersterling, Horst Dieter; Varga, Margit Bromous acid/cerium(4+): reaction and HBrO2 disproportionation measured in sulfuric acid solution at different acidities. J. Phys. Chem. 1993, 97 (30), 7932–38. DOI: 10.1021/j100132a022.
- ↑ Pelle, Krisztina; Wittmann, Maria; Lovrics, Klára; Noszticzius, Zoltán; Turco Liveri, Maria L.; Lombardo, Renato Mechanistic Investigations of the BZ Reaction with Oxalic Acid Substrate. I. The Oscillatory Parameter Region and Rate Constants Measured for the Reactions of HOBr, HBrO2, and Acidic BrO3− with Oxalic Acid. J. Phys. Chem. A 2004, 108 (25), 5377–85. DOI: 10.1021/jp048817s. Onel, Lavinia; Bourceanu, Gelu; Bitter, István; Wittmann, Mária; Noszticzius, Zoltán Uncatalyzed Reactions in the Classical Belousov−Zhabotinsky System. 2. The Malonic Acid−Bromate Reaction in Acidic Media. J. Phys. Chem. A 2006, 110 (3), 990–96. DOI: 10.1021/jp055259o.
External links
 |
See also the corresponding article on Wikipedia. |
| Error creating thumbnail: Unable to save thumbnail to destination |
This page is currently licensed under the Creative Commons Attribution 3.0 Unported license and any later versions of that license. |
