Difference between revisions of "Perbromate"
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==Perbromate esters== | ==Perbromate esters== | ||
| + | [[Isopropyl perbromate]] has been prepared by the reaction of [[silver perbromate]] with [[2-bromopropane]] at −20 °C: it is stable in solution at −20 °C, but decomposes to [[acetone]] with a half-life of 30 minutes at room temperature.<ref>{{citation | title = Preparation of an alkyl perbromate | first1 = Kurt | last1 = Baum | first2 = Charles D. | last2 = Beard | first3 = Vytautas | last3 = Grakauskas | journal = J. Am. Chem. Soc. | year = 1975 | volume = 97 | issue = 2 | pages = 267–68 | doi = 10.1021/ja00835a005}}. {{citation | inventor1-last = Baum | inventor1-first = Kurt | inventor2-last = Beard | inventor2-first = Charles D. | inventor3-last = Grakaukas | inventor3-first = Vitautas | assignee = U.S. Dept. of the Navy | title = Preparation of alkyl perbromates | country-code = US | patent-number = 4022811 | publication-date = 1977-10-05}}.</ref> | ||
==Notes and references== | ==Notes and references== | ||
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*{{citation | first1 = Ulrik K. | last1 = Klaening | first2 = Kjeld J. | last2 = Olsen | first3 = Evan H. | last3 = Appelman | title = Photolysis of perbromate in aqueous solution | journal = J. Chem. Soc., Faraday Trans. 1 | volume = 71 | pages = 473–84 | year = 1975 | doi = 10.1039/F19757100473}}. | *{{citation | first1 = Ulrik K. | last1 = Klaening | first2 = Kjeld J. | last2 = Olsen | first3 = Evan H. | last3 = Appelman | title = Photolysis of perbromate in aqueous solution | journal = J. Chem. Soc., Faraday Trans. 1 | volume = 71 | pages = 473–84 | year = 1975 | doi = 10.1039/F19757100473}}. | ||
*{{citation | first1 = K. J. | last1 = Olsen | first2 = K. | last2 = Sehested | first3 = E. H. | last3 = Appelman | title = Pulse-radiolysis of aqueous KBrO<sub>4</sub> solutions | journal = Chem. Phys. Lett. | volume = 19 | issue = 2 | pages = 213–14 | year = 1973 | doi = 10.1016/0009-2614(73)85057-2}}. | *{{citation | first1 = K. J. | last1 = Olsen | first2 = K. | last2 = Sehested | first3 = E. H. | last3 = Appelman | title = Pulse-radiolysis of aqueous KBrO<sub>4</sub> solutions | journal = Chem. Phys. Lett. | volume = 19 | issue = 2 | pages = 213–14 | year = 1973 | doi = 10.1016/0009-2614(73)85057-2}}. | ||
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==External links== | ==External links== | ||
Revision as of 08:08, 6 January 2011
| 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 | tetrahedral: r(Br–O) = 161 pm |
| Thermochemistry[2][3] | |
| Std enthalpy of formation ΔfH |
+12.1 kJ mol−1 (aq) |
| Std Gibbs energy of formation ΔfG |
+120.8 kJ mol−1 (aq) |
| Standard molar entropy S |
187 J K−1 mol−1 (aq) |
| 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.[5][6][7] However, they are kinetically quite inert, especially in dilute solution.[6][7][8]
Contents
History
Although perchlorates and periodates have been known since the early nineteenth century, perbromates proved far more elusive.[9][10] The first claim of preparation came in 1863,[11] but proved unrepeatable.[12][13] Several later attempts to prepare perbromates were equally unsuccessful.[14][15] Some authors surmised that perbromates were fundamentally unstable.[16][17]
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 SeO2−4 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.[5]
Electrolysis of lithium bromate at a platinum anode gave a yield of about 2% perbromate.[5] 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.[5]
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.[19]
Structure
| r(Br–O)/pm | Ref. | |
|---|---|---|
| CsBrO4 | 159.1 | [20] |
| NaBrO4·H2O | 160.2 | [21] |
| [Co(H2O)6](BrO4)2 | 160.5 | [22] |
| LiBrO4·3H2O | 160.6 | [23] |
| Ca(BrO4)2·3H2O | 160.7 | [24] |
| Ba(BrO4)2·3H2O | 160.8 | [25] |
| EXAFS | 161 | [1] |
| [Ni(H2O)6](BrO4)2 | 162.9 | [26] |
The perbromate ion has Td symmetry.
Properties
Perbromate esters
Isopropyl perbromate has been prepared by the reaction of silver perbromate with 2-bromopropane at −20 °C: it is stable in solution at −20 °C, but decomposes to acetone with a half-life of 30 minutes at room temperature.[27]
Notes and references
Notes
- ↑ Perbromic acid is fully dissociated in solution. By analogy with perchloric acid,[4] 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).[18]
References
- ↑ 1.0 1.1 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.
- ↑ 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.
- ↑ Lee, C. L.; Lister, M. W. The Decomposition of Aqueous Sodium Bromite. Can. J. Chem. 1971, 49 (17), 2822–26. DOI: 10.1139/v71-470.
- ↑ Olovsson, Ivar Hydrogen-Bond Studies. XXIX. Crystal Structure of Perchloric Acid Dihydrate, H5O2+ClO4−. J. Chem. Phys. 1968, 49 (3), 1063–67. DOI: 10.1063/1.1670193.
- ↑ 5.0 5.1 5.2 5.3 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.
- ↑ 6.0 6.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1020–22. ISBN 0-08-022057-6.
- ↑ 7.0 7.1 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.
- ↑ Herrell, A. Y.; Gayer, K. H. The elusive perbromates. J. Chem. Educ. 1972, 49 (9), 583. DOI: 10.1021/ed049p583.
- ↑ Appelman, Evan H. Nonexistent compounds. Two case histories. Acc. Chem. Res. 1973, 6 (4), 113–17. DOI: 10.1021/ar50064a001.
- ↑ 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.
- ↑ Gebert, Elizabeth; Peterson, Selmer W.; Reis, Arthur H., Jr.; Appelman, Evan H. The crystal structure of cesium perbromate. J. Inorg. Nucl. Chem. 1981, 43 (12), 3085–89. DOI: 10.1016/0022-1902(81)80067-X.
- ↑ Blackburn, A. C.; Gallucci, J. C.; Gerkin, R. E.; Reppart, W. J. Structure of sodium perbromate monohydrate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1992, 48 (3), 419–24. DOI: 10.1107/S0108270191010818.
- ↑ Blackburn, A. C.; Gerkin, R. E. Structure of hexaaquacobalt(II) perbromate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1993, 49 (7), 1271–75. DOI: 10.1107/S0108270192013465.
- ↑ Blackburn, A. C.; Gallucci, J. C.; Gerkin, R. E.; Reppart, W. J. Structure of lithium perbromate trihydrate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1993, 49 (8), 1437–39. DOI: 10.1107/S0108270193000538.
- ↑ Blackburn, A. C.; Gerkin, R. E. Structure of tetraaquacalcium perbromate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1993, 49 (8), 1439–42. DOI: 10.1107/S0108270193001714.
- ↑ Gerkin, R. E.; Reppart, W. J.; Appelman, E. H. The structure of barium perbromate trihydrate Ba(BrO4)2.3H2O. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1988, 44 (6), 960–62. DOI: 10.1107/S0108270188002215.
- ↑ Gallucci, J. C.; Gerkin, R. E.; Reppart, W. J. Structure of nickel(II) perbromate hexahydrate at 296 K. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1990, 46 (9), 1580–84. DOI: 10.1107/S0108270189013533.
- ↑ 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.
Further reading
- 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.
External links
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