Difference between revisions of "Hypobromous acid"
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| Section2 = {{Chembox Properties | | Section2 = {{Chembox Properties | ||
| − | | Reference = <ref name=" | + | | Reference = <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> |
| Formula = HOBr | | Formula = HOBr | ||
| MolarMass = 96.911 g mol<sup>−1</sup> | | MolarMass = 96.911 g mol<sup>−1</sup> | ||
| − | | pKa = 8. | + | | pKa = 8.80 |
}} | }} | ||
| Section3 = {{Chembox Structure | | Section3 = {{Chembox Structure | ||
| Line 23: | Line 23: | ||
| OtherFunctn = [[Hypofluorous acid]]<br/>[[Hypochlorous acid]]<br/>[[Hypoiodous acid]] | | OtherFunctn = [[Hypofluorous acid]]<br/>[[Hypochlorous acid]]<br/>[[Hypoiodous acid]] | ||
| Function = hypohalous acids | | Function = hypohalous acids | ||
| − | | OtherCpds = [[Hydrobromic acid]]<br/>[[Bromic acid]] | + | | OtherCpds = [[Hydrobromic acid]]<br/>[[Bromous acid]]<br/>[[Bromic acid]]<br/>[[Perbromic acid]] |
}} | }} | ||
}} | }} | ||
| − | '''Hypobromous acid''', HOBr, is an [[oxoacid]] of [[bromine]]. It is often considered to be only stable in aqueous solution,<ref name=" | + | '''Hypobromous acid''', HOBr, is an [[oxoacid]] of [[bromine]]. It is often considered to be only stable in aqueous solution,<ref name="G&E">{{Greenwood&Earnshaw1st|pages=999–1007}}.</ref><ref name="C&W">{{Cotton&Wilkinson5th|pages=563–67}}.</ref> but it can be prepared in sufficient quantities in the gas phase for spectroscopic studies.<ref name="v1"/> |
==Preparation== | ==Preparation== | ||
| + | Hypobromous acid can be prepared in solution by the reaction of [[bromine]] with a well-stirred suspension of [[mercury(II) oxide]] or with [[silver nitrate]].<ref>{{citation | first1 = A. J. | last1 = Downs | first2 = C. J. | last2 = Adams | editor1-first = J. C., Jr. | editor1-last = Bailar | editor2-first = H. J. | editor2-last = Emeleus | editor3-first = R. | editor3-last = Nyholm | editor4-first = A. F. | editor4-last = Trotman-Dickenson | title = Comprehensive Inorganic Chemistry | volume = 2 | publisher = Pergamon | location = Oxford | year = 1973 | page = 1400}}.</ref> | ||
| + | :2 Br<sub>2</sub> + 2 HgO + H<sub>2</sub>O → 2 HOBr + HgO·HgBr<sub>2</sub> | ||
| + | :Br<sub>2</sub> + AgNO<sub>3</sub> + H<sub>2</sub>O → HOBr + AgBr + HNO<sub>3</sub> | ||
| + | It is also formed by the [[disproportionation]] of bromine in water, although the equilibrium concentration is only {{nowrap|1.15{{e|−3}} mol dm<sup>−3</sup>}} in a saturated bromine solution ({{nowrap|0.21 mol dm<sup>−3</sup>}}) at 25 °C.<ref name="C&W"/> | ||
| + | :Br<sub>2</sub> + H<sub>2</sub>O {{eqm}} HOBr + H<sup>+</sup> + Br<sup>−</sup> | ||
| + | It can also be prepared by the reaction of water with [[dibromine monoxide]], which is the formal anhydride of hypobromous acid.<ref name="Kirk-Othmer"/> | ||
| + | :Br<sub>2</sub>O + H<sub>2</sub>O {{eqm}} 2 HOBr | ||
==Structure== | ==Structure== | ||
| + | Hypobromous acid has a bent ''C''<sub>2v</sub> structure in the vapour phase, as expected from [[VSEPR theory]], with ''r''(Br–O) = 182.80 pm, ''θ''(H–O–Br) = 102.99°.<ref name="v1"/> Its [[Rotational spectroscopy|rotational spectrum]] has been extensively studied.<ref>{{citation | first1 = Yoshinori | last1 = Koga | first2 = Harutoshi | last2 = Takeo | first3 = Shigeo | last3 = Kondo | first4 = Masaaki | last4 = Sugie | first5 = Chi | last5 = Matsumura | first6 = G. A. | last6 = McRae | first7 = E. A. | last7 = Cohen | title = The rotational spectra, molecular structure, dipole moment, and hyperfine constants of HOBr and DOBr | journal = J. Mol. Spectrosc. | volume = 138 | issue = 2 | year = 1989 | pages = 467–81 | doi = 10.1016/0022-2852(89)90013-1}}.</ref><ref>{{citation | first1 = G. A. | last1 = McRae | first2 = E. A. | last2 = Cohen | title = The ν<sub>2</sub> band of HOBr | journal = J. Mol. Spectrosc. | volume = 139 | issue = 2 | year = 1990 | pages = 369–76 | doi = 10.1016/0022-2852(90)90074-Z}}.</ref><ref>{{citation | first1 = J. | last1 = Orphal | first2 = Q. | last2 = Kou | first3 = F. | last3 = Kwabia Tchana | first4 = O. | last4 = Pirali | first5 = J.-M. | last5 = Flaud | title = The ν<sub>3</sub> bands of HOBr around 16 μm measured by high-resolution Fourier-transform spectroscopy | journal = J. Mol. Spectrosc. | volume = 221 | issue = 2 | year = 2003 | pages = 239–43 | doi = 10.1016/S0022-2852(03)00222-4}}.</ref><ref>{{citation | first1 = J. | last1 = Orphal | first2 = J.-M. | last2 = Flaud | first3 = Q. | last3 = Kou | first4 = F. | last4 = Kwabia Tchana | first5 = O. | last5 = Pirali | title = The far infrared rotational spectrum of HOBr: line positions and intensities | journal = J. Mol. Struct. | volume = 742 | issue = 1–3 | year = 2005 | pages = 153–59 | doi = 10.1016/j.molstruc.2005.01.006}}.</ref><ref>{{citation | first1 = E. A. | last1 = Cohen | first2 = H. S. P. | last2 = Müller | first3 = T. L. | last3 = Tan | first4 = G. A. | last4 = McRae | title = High resolution spectroscopy of DOBr and molecular properties of hypobromous acid | journal = J. Mol. Spectrosc. | volume = 262 | issue = 1 | year = 2010 | pages = 30–36 | doi = 10.1016/j.jms.2010.04.009}}.</ref> | ||
==Reactivity== | ==Reactivity== | ||
| + | Hypobromous acid is unstable with respect to [[disproportionation]], and should be prepared at around 0 °C.<ref name="C&W"/> | ||
| + | :3 HOBr → 3 H<sup>+</sup> + 2 Br<sup>−</sup> + BrO{{su|b=3|p=−}} | ||
| + | The rate of disproportionation depends on the pH, being highest for pH 3–8.<ref name="disprop">{{citation | first1 = Richard C. | last1 = Beckwith | first2 = Dale W. | last2 = Margerum | title = Kinetics of Hypobromous Acid Disproportionation | journal = Inorg. Chem., 1997 | volume = 36 | issue =17 | pages = 3754–60 | doi = 10.1021/ic970155g}}.</ref> The reaction is catalyzed by several species, including [[cobalt]], [[nickel]] and [[copper]] ions<ref name="Kirk-Othmer"/> and [[phosphate]] and [[carbonate]].<ref name="disprop"/> | ||
| + | |||
| + | Hypobromous acid will add to carbon–carbon double bonds to give [[bromohydrin]]s,<ref>{{citation | last = Mokievsky | journal = Zh. Russ. Fiz.-Khim. O-va. | volume = 30 | pages = 900 | year = 1898}}; {{citation | journal = Chem. Zentralbl. | volume = 1 | page = 591 | year = 1899}}.</ref><ref>{{citation | last1 = Ingold | first1 = Christopher Kelk | last2 = Smith | first2 = Henry Geoffrey | title = CCCLXXXII.—The modes of addition to conjugated unsaturated systems. Part III. Further remarks and observations bearing on the mechanism of addition of halogens and hydrogen halides | journal = J. Chem. Soc. | year = 1931 | pages = 2752–65 | doi = 10.1039/JR9310002752}}.</ref> and will also brominate activated aromatic rings such as [[toluene]].<ref>{{citation | last = Stark | first = O. | title = Über ein neues Bromierungsverfahren, Bromieren mit wäßriger, unterbromiger Säure | journal = Ber. Dtsch. Chem. Ges. | volume = 43 | issue = 1 | pages = 670–74 | year = 1910 | doi = 10.1002/cber.191004301113}}.</ref> | ||
| + | |||
| + | The [[salt]]s of hypobromous acid are called [[hypobromite]]s. Because HOBr is only a very weak acid (p''K''<sub>a</sub> = 8.90), only salts of strong bases, such as the [[Alkali metal|alkali]] and [[alkaline earth metal]] [[hydroxide]]s, can be formed. [[Lithium hypobromite|Lithium]], [[Sodium hypobromite|sodium]] and [[potassium hypobromite]]s have well-defined solid hydrates.<ref>{{citation | first1 = M. T. | last1 = Kelley | first2 = D. E. | last2 = LaValle | first3 = R. B. | last3 = Quincy | contribution = Inorganic Preparations | title = Analytical Chemistry Division Annual Progress Report For Period Ending November 15, 1965 | url = http://www.ornl.gov/info/reports/1966/3445605481993.pdf | editor-first = Helen P. | editor-last = Raaen | publisher = Oak Ridge National Laboratory | location = Oak Ridge, Tenn. | year = 1966 | id = ORNL-3889 | pages = 71–73}}.</ref><ref>{{citation | first1 = R. | last1 = Scholder | first2 = K. | last2 = Krauss | title = Über Kristallisierte Alkalihypobromite | journal = Z. Anorg. Allg. Chem. | volume = 268 | issue = 4–6 | pages = 279–90 | year = 1952 | doi = 10.1002/zaac.19522680410}}.</ref> [[Calcium hypobromite]] has been known as a bleaching agent since the early twentieth century, and probably has the formula CaBr(OBr).<ref name="Kirk-Othmer"/> Other hypobromites are likely to exist in solution. | ||
==Notes and references== | ==Notes and references== | ||
| Line 39: | Line 54: | ||
===References=== | ===References=== | ||
| − | {{reflist}} | + | {{reflist|2}} |
==External links== | ==External links== | ||
| Line 45: | Line 60: | ||
[[Category:Bromine oxoacids]] | [[Category:Bromine oxoacids]] | ||
| + | [[Category:Hypobromites|*]] | ||
{{CC-BY-3.0}} | {{CC-BY-3.0}} | ||
Latest revision as of 17:51, 1 January 2011
| Hypobromous acid | |
|---|---|
| IUPAC name | Hypobromous acid[note 1] |
| Other names | Bromic(I) acid Bromanol Hydroxidobromine |
| Identifiers | |
| InChI | InChI=1/BrHO/c1-2/h2H |
| InChIKey | CUILPNURFADTPE-UHFFFAOYAL |
| Standard InChI | InChI=1S/BrHO/c1-2/h2H |
| Standard InChIKey | CUILPNURFADTPE-UHFFFAOYSA-N |
| CAS number | [] |
| ChemSpider | |
| Properties[2] | |
| Chemical formula | HOBr |
| Molar mass | 96.911 g mol−1 |
| Acidity (pKa) | 8.80 |
| Structure[3] | |
| Molecular geometry | bent: r(Br–O) = 182.80 pm, θ(Br–O–H) = 102.99° |
| Related compounds | |
| Other hypohalous acids | Hypofluorous acid Hypochlorous acid Hypoiodous acid |
| Other compounds | Hydrobromic acid Bromous acid Bromic acid Perbromic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Hypobromous acid, HOBr, is an oxoacid of bromine. It is often considered to be only stable in aqueous solution,[4][5] but it can be prepared in sufficient quantities in the gas phase for spectroscopic studies.[3]
Contents
Preparation
Hypobromous acid can be prepared in solution by the reaction of bromine with a well-stirred suspension of mercury(II) oxide or with silver nitrate.[6]
- 2 Br2 + 2 HgO + H2O → 2 HOBr + HgO·HgBr2
- Br2 + AgNO3 + H2O → HOBr + AgBr + HNO3
It is also formed by the disproportionation of bromine in water, although the equilibrium concentration is only 1.15 × 10−3 mol dm−3 in a saturated bromine solution (0.21 mol dm−3) at 25 °C.[5]
- Br2 + H2O ⇌ HOBr + H+ + Br−
It can also be prepared by the reaction of water with dibromine monoxide, which is the formal anhydride of hypobromous acid.[2]
- Br2O + H2O ⇌ 2 HOBr
Structure
Hypobromous acid has a bent C2v structure in the vapour phase, as expected from VSEPR theory, with r(Br–O) = 182.80 pm, θ(H–O–Br) = 102.99°.[3] Its rotational spectrum has been extensively studied.[7][8][9][10][11]
Reactivity
Hypobromous acid is unstable with respect to disproportionation, and should be prepared at around 0 °C.[5]
- 3 HOBr → 3 H+ + 2 Br− + BrO−3
The rate of disproportionation depends on the pH, being highest for pH 3–8.[12] The reaction is catalyzed by several species, including cobalt, nickel and copper ions[2] and phosphate and carbonate.[12]
Hypobromous acid will add to carbon–carbon double bonds to give bromohydrins,[13][14] and will also brominate activated aromatic rings such as toluene.[15]
The salts of hypobromous acid are called hypobromites. Because HOBr is only a very weak acid (pKa = 8.90), only salts of strong bases, such as the alkali and alkaline earth metal hydroxides, can be formed. Lithium, sodium and potassium hypobromites have well-defined solid hydrates.[16][17] Calcium hypobromite has been known as a bleaching agent since the early twentieth century, and probably has the formula CaBr(OBr).[2] Other hypobromites are likely to exist in solution.
Notes and references
Notes
- ↑ Hypobromous 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>.
- ↑ 2.0 2.1 2.2 2.3 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.
- ↑ 3.0 3.1 3.2 Cohen, E. A.; Mcrae, G. A.; Tan, T. L.; Friedl, R. R.; Johns, J. W. C.; Noel, M. The ν1 Band of HOBr. J. Mol. Spectrosc. 1995, 173 (1), 55–61. DOI: 10.1006/jmsp.1995.1218.
- ↑ Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 999–1007. ISBN 0-08-022057-6.
- ↑ 5.0 5.1 5.2 Cotton, F. Albert; Wilkinson, Geoffrey Advanced Inorganic Chemistry, 5th ed.; Wiley-Interscience: New York, 1988; pp 563–67. ISBN 0-471-84997-9.
- ↑ Downs, A. J.; Adams, C. J. In Comprehensive Inorganic Chemistry; Bailar, J. C., Jr.; Emeleus, H. J.; Nyholm, R., et al., Eds.; Pergamon: Oxford, 1973; Vol. 2, p 1400.
- ↑ Koga, Yoshinori; Takeo, Harutoshi; Kondo, Shigeo; Sugie, Masaaki; Matsumura, Chi; McRae, G. A.; Cohen, E. A. The rotational spectra, molecular structure, dipole moment, and hyperfine constants of HOBr and DOBr. J. Mol. Spectrosc. 1989, 138 (2), 467–81. DOI: 10.1016/0022-2852(89)90013-1.
- ↑ McRae, G. A.; Cohen, E. A. The ν2 band of HOBr. J. Mol. Spectrosc. 1990, 139 (2), 369–76. DOI: 10.1016/0022-2852(90)90074-Z.
- ↑ Orphal, J.; Kou, Q.; Kwabia Tchana, F.; Pirali, O.; Flaud, J.-M. The ν3 bands of HOBr around 16 μm measured by high-resolution Fourier-transform spectroscopy. J. Mol. Spectrosc. 2003, 221 (2), 239–43. DOI: 10.1016/S0022-2852(03)00222-4.
- ↑ Orphal, J.; Flaud, J.-M.; Kou, Q.; Kwabia Tchana, F.; Pirali, O. The far infrared rotational spectrum of HOBr: line positions and intensities. J. Mol. Struct. 2005, 742 (1–3), 153–59. DOI: 10.1016/j.molstruc.2005.01.006.
- ↑ Cohen, E. A.; Müller, H. S. P.; Tan, T. L.; McRae, G. A. High resolution spectroscopy of DOBr and molecular properties of hypobromous acid. J. Mol. Spectrosc. 2010, 262 (1), 30–36. DOI: 10.1016/j.jms.2010.04.009.
- ↑ 12.0 12.1 Beckwith, Richard C.; Margerum, Dale W. Kinetics of Hypobromous Acid Disproportionation. Inorg. Chem., 1997, 36 (17), 3754–60. DOI: 10.1021/ic970155g.
- ↑ Mokievsky Zh. Russ. Fiz.-Khim. O-va. 1898, 30, 900; Chem. Zentralbl. 1899, 1, 591.
- ↑ Ingold, Christopher Kelk; Smith, Henry Geoffrey CCCLXXXII.—The modes of addition to conjugated unsaturated systems. Part III. Further remarks and observations bearing on the mechanism of addition of halogens and hydrogen halides. J. Chem. Soc. 1931, 2752–65. DOI: 10.1039/JR9310002752.
- ↑ Stark, O. Über ein neues Bromierungsverfahren, Bromieren mit wäßriger, unterbromiger Säure. Ber. Dtsch. Chem. Ges. 1910, 43 (1), 670–74. DOI: 10.1002/cber.191004301113.
- ↑ Kelley, M. T.; LaValle, D. E.; Quincy, R. B. Inorganic Preparations. In Analytical Chemistry Division Annual Progress Report For Period Ending November 15, 1965; Raaen, Helen P., Ed.; Oak Ridge National Laboratory: Oak Ridge, Tenn., 1966; pp 71–73. ORNL-3889, <http://www.ornl.gov/info/reports/1966/3445605481993.pdf>.
- ↑ Scholder, R.; Krauss, K. Über Kristallisierte Alkalihypobromite. Z. Anorg. Allg. Chem. 1952, 268 (4–6), 279–90. DOI: 10.1002/zaac.19522680410.
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