Perbromate

In chemistry, the perbromate ion is the anion having the chemical formula BrO−
4. It is an oxyanion of bromine, the conjugate base of perbromic acid, in which bromine has the oxidation state +7.[1] Unlike its chlorine (ClO−4) and iodine (IO−4) analogs, it is difficult to synthesize.[2] It has tetrahedral molecular geometry.[3]

Perbromate

Space-filling model of the perbromate anion, BrO−
4
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
  • InChI=1S/BrHO4/c2-1(3,4)5/h(H,2,3,4,5)/p-1
    Key: LLYCMZGLHLKPPU-UHFFFAOYSA-M
  • [O-]Br(=O)(=O)=O
Properties
BrO4−
Molar mass 143.901 g·mol−1
Related compounds
Related compounds
 bromide
hypobromite
bromite
bromate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

The term perbromate also refers to a compound that contains the BrO−
4 anion or the –OBrO
3 functional group.

The perbromate ion is a strong oxidizing agent.[2] The reduction potential for the BrO−
4/Br− couple is +0.68 V at pH 14. This is comparable to selenite's reduction potential.

Synthesis

Attempted syntheses of perbromates were unsuccessful until 1968, when it was finally obtained by the beta decay of selenium-83 in a selenate salt:[4][5]

83
SeO2−
4 → 83
BrO−
4 + β−

Subsequently, it was successfully synthesized again by the electrolysis of LiBrO
3, although only in low yield.[5][6] Later, it was obtained by the oxidation of bromate with xenon difluoride.[3][7] Once perbromates are obtained, perbromic acid can be produced by protonating BrO−
4.[2]

One effective method of producing perbromate is by the oxidation of bromate with fluorine under alkaline conditions:[2][8]

BrO−
3 + F
2 + 2 OH−
 → BrO−
4 + 2 F−
 + H
2O

This synthesis is much easier to perform on a large scale than the electrolysis route or oxidation by xenon difluoride.[8]

In 2011 a new, more effective synthesis was discovered: perbromate ions were formed through the reaction of hypobromite and bromate ions in an alkaline sodium hypobromite solution. The reaction (and its perchlorate analogue) occurs naturally, but very slowly, requiring several days to complete.[9]

Diperiodatonickelate anions in alkaline solution can oxidise bromate to perbromate. This is a relatively lower cost and fluorine free synthesis.[10]

See also

Other bromine anions:

Bromine oxidation state −1 +1 +3 +5 +7
Name bromide hypobromite bromite bromate perbromate
Formula Br− BrO− BrO−
2		 BrO−
3		 BrO−
4
Structure

References
  1. Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. p. 439. ISBN 0-12-352651-5.
  2. W. Henderson (2000). Main group chemistry (Volume 3 of Tutorial chemistry texts). Royal Society of Chemistry. pp. 136–137. ISBN 0-85404-617-8.
  3. Kurt H. Stern (2001). High temperature properties and thermal decomposition of inorganic salts with oxyanions. CRC Press. p. 224. ISBN 0-8493-0256-0.
  4. Appelman, E. H. (1973). "Nonexistent compounds. Two case histories". Accounts of Chemical Research. 6 (4): 113–117. doi:10.1021/ar50064a001.
  5. Appelman, E. H. (1968). "Synthesis of perbromates". Journal of the American Chemical Society. 90 (7): 1900–1901. doi:10.1021/ja01009a040.
  6. Kenneth Malcolm Mackay; W. Henderson (2002). Rosemary Ann Mackay (ed.). Introduction to modern inorganic chemistry (6th ed.). CRC Press. p. 488. ISBN 0-7487-6420-8.
  7. Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. p. 395. ISBN 0-12-352651-5.
  8. Appelman, E. H. (1969). "Perbromic acid and perbromates: synthesis and some properties". Inorg. Chem. 8 (2): 223–227. doi:10.1021/ic50072a008.
  9. Pisarenko, Aleksey N.; Young, Robert; Quiñones, Oscar; J. Vanderford, Brett; B. Mawhinney, Douglas (2011). "Two New Methods of Synthesis for the Perbromate Ion: Chemistry and Determination by LC-MS/MS". Inorg. Chem. 50 (18): 8691–8693. doi:10.1021/ic201329q. PMID 21780765.
  10. Bilehal, Dinesh C.; Kulkarni, Raviraj M.; Nandibewoor, Sharanappa T. (January 2002). "Kinetics and Mechanism of Oxidation of Bromate by Diperiodatonickelate(IV) in Aqueous Alkaline Medium--A Simple Method for Formation of Perbromate". Inorganic Reaction Mechanisms. 4 (1–2): 103–109. doi:10.1080/1028662021000020244.
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