Hypobromous acid
| 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]
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 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.
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