Perbromate
| Perbromate | |
|---|---|
| Other names | Tetraoxidobromate(1−) |
| Identifiers | |
| InChI | InChI=1/BrHO4/c2-1(3,4)5/h(H,2,3,4,5)/p-1 |
| InChIKey | LLYCMZGLHLKPPU-REWHXWOFAT |
| Standard InChI | InChI=1S/BrHO4/c2-1(3,4)5/h(H,2,3,4,5)/p-1 |
| Standard InChIKey | LLYCMZGLHLKPPU-UHFFFAOYSA-M |
| CAS number | [] |
| ChemSpider | |
| Structure[1] | |
| Molecular geometry | r(Br–O) = 161 pm |
| Related compounds | |
| Other anions | Perchlorate Periodate Hypobromite Bromite Bromate |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
A perbromate is a salt or ester of perbromic acid. Perbromates, including perbromic acid,[note 1] are the only well-characterized compounds of bromine in the +7 oxidation state.
Perbromates are thermodynamically more oxidizing than perchlorates or periodates, and eluded preparation for more than 100 years until 1968.[2][3][4] However, they are kinetically quite inert, especially in dilute solution.[3][4][5]
Contents
History
Although perchlorates and periodates have been known since the early nineteenth century, perbromates proved far more elusive. The first claim of preparation came in 1863,[6] but proved unrepeatable.[7][8] Several later attempts to prepare perbromates were equally unsuccessful.[9][10] Some authors surmised that perbromates were fundamentally unstable.[11][12]
The first clear evidence of the existence of the perbromate anion came from "hot-atom" techniques. A sample of the β−-emittor selenium-83 (t½ = 25 min) was prepared in the form of the selenate anion SeO−4 and allowed to decay into bromine-83. Approximately 14% of the 83Br activity (β−, t½ = 2.4 h) coprecipitated with rubidium perchlorate, as expected for a perbromate species.[2]
Electrolysis of lithium bromate at a platinum anode gave a yield of about 2% perbromate.[2] Small amounts of perbromate (1–4% yield) were also formed by the xenon difluoride oxidation of bromates, while perxenate, peroxodisulfate and ozone were ineffective as oxidizing agents.[2]
Preparation
The preparation of macroscopic quantities of perbromates relies on the oxidation of sodium bromate[note 2] in alkaline solution (5 M sodium hydroxide) by gaseous fluorine:
- BrO−3 + F2 + 2 OH− → BrO−4 + 2 F− + H2O
The yield is about 20%, and the reaction can be operated on a 100-gram scale. Perbromic acid can be prepared from the resulting sodium perbromate by ion exchange, and used to prepare other perbromates.[14]
Notes and references
Notes
- ↑ Perbromic acid is fully dissociated in solution. By analogy with perchloric acid, the solid HBrO4·2H2O is expected to contain [(H2O)2H]+[BrO4]−.
- ↑ Sodium bromate is used as the resulting sodium perbromate is very soluble in water; potassium perbromate is much less soluble (as is the case with the corresponding perchlorates).[13]
References
- ↑ Levason, William; Ogden, J. Steven; Spicer, Mark D.; Young, Nigel A. Characterisation of the oxo-anions of bromine BrOx− (x = 1–4) by infrared, Raman, nuclear magnetic resonance, and bromine K-edge extended X-ray absorption fine structure techniques. J. Chem. Soc., Dalton Trans. 1990 (1), 349–53. DOI: 10.1039/DT9900000349.
- ↑ 2.0 2.1 2.2 2.3 Appelman, Evan H. The Synthesis of Perbromates. J. Am. Chem. Soc. 1968, 90 (7), 1900–1. DOI: 10.1021/ja01009a040. Appelman, Evan H. Perbromic acid and perbromates: synthesis and some properties. Inorg. Chem. 1969, 8 (2), 223–27. DOI: 10.1021/ic50072a008.
- ↑ 3.0 3.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1020–22. ISBN 0-08-022057-6.
- ↑ 4.0 4.1 Cotton, F. Albert; Wilkinson, Geoffrey Advanced Inorganic Chemistry, 5th ed.; Wiley-Interscience: New York, 1988; pp 568–69. ISBN 0-471-84997-9.
- ↑ Kjaer, A. M.; Ulstrup, J. Electron-transfer reactions between the perbromate ion and iron(II) complexes of 2,2'-bipyridine and substituted 1,10-phenanthrolines. Inorg. Chem. 1982, 21 (9), 3490–94. DOI: 10.1021/ic00139a044.
- ↑ Kämmerer, Hermann Notizen. J. Prakt. Chem. 1863, 90, 190. DOI: 10.1002/prac.18630900126. Kaemmerer, Hermann Studien über die Sauerstoffverbindungen der Halogene. Ann. Phys. (Berlin) 1869, 214 (11), 390–417. DOI: 10.1002/andp.18692141104.
- ↑ Pattison Muir, M. M. Note on the perbromates. J. Chem. Soc. 1876, 30, 469. DOI: 10.1039/JS8763000469.
- ↑ Wolfram, Guido Ueber die Darstellung der Perbromsäure. Justus Liebigs Ann. Chem. 1879, 198 (1–2), 95–98. DOI: 10.1002/jlac.18791980107.
- ↑ Cook, Ernest H. Effect of heat on iodates and bromates. I. Potassic iodate and bromate. J. Chem. Soc., Trans. 1894, 65, 802–14. DOI: 10.1039/CT8946500802.
- ↑ Bancroft, G. M.; Gesser, H. D. The search for perbromate—I: The thermal decomposition of bromates. J. Inorg. Nucl. Chem. 1965, 27 (7), 1545–56. DOI: 10.1016/0022-1902(65)80016-1.
- ↑ Hugus, Z. Z., Jr. The Possible Use of 4f Orbitals in Bonding: the Enhanced Stability of the Higher Oxidation States of Iodine, Tellurium and Antimony; the Non-existence of Perbromic Acid. J. Am. Chem. Soc. 1952, 74 (4), 1076–77. DOI: 10.1021/ja01124a502.
- ↑ Urch, D. S. The perbromate problem. J. Inorg. Nucl. Chem. 1963, 25 (7), 771–78. DOI: 10.1016/0022-1902(63)80360-7.
- ↑ 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.
- ↑ Appelman, E. H. Perbromic acid and potassium perbromate. Inorg. Synth. 1972, 13, 1–9. DOI: 10.1002/9780470132449.ch1.
Further reading
- Appelman, Evan H. Nonexistent compounds. Two case histories. Acc. Chem. Res. 1973, 6 (4), 113–17. DOI: 10.1021/ar50064a001.
- Johnson, Gerald K.; Smith, Peter N.; Appelman, Evan H.; Hubbard, Ward N. Thermodynamic properties of the perbromate and bromate ions. Inorg. Chem. 1970, 9 (1), 119–25. DOI: 10.1021/ic50083a025.
- Schreiner, Felix; Osborne, Darrell W.; Pocius, Alphonsus V.; Appelman, Evan H. Heat capacity of potassium perbromate, KBrO4, between 5 and 350°K. Inorg. Chem. 1970, 9 (10), 2320–24. DOI: 10.1021/ic50092a024.
- Klaening, Ulrik K.; Olsen, Kjeld J.; Appelman, Evan H. Photolysis of perbromate in aqueous solution. J. Chem. Soc., Faraday Trans. 1 1975, 71, 473–84. DOI: 10.1039/F19757100473.
- Olsen, K. J.; Sehested, K.; Appelman, E. H. Pulse-radiolysis of aqueous KBrO4 solutions. Chem. Phys. Lett. 1973, 19 (2), 213–14. DOI: 10.1016/0009-2614(73)85057-2.
- Baum, Kurt; Beard, Charles D.; Grakauskas, Vytautas Preparation of an alkyl perbromate. J. Am. Chem. Soc. 1975, 97 (2), 267–68. DOI: 10.1021/ja00835a005. Baum, Kurt; Beard, Charles D.; Grakaukas, Vitautas (U.S. Dept. of the Navy) Preparation of alkyl perbromates. US Patent 4022811, published 5 October 1977.
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