Perbromate

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Space-filling model of the perbromate anion, BrO4

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 and iodine analogs (perchlorate and periodate), it is difficult to synthesize.[2] It has tetrahedral molecular geometry.[3]

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 BrO4/Br couple is +0.68 V at pH 14. This is comparable to selenite's reduction potential.

Synthesis[edit]

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]

83SeO42−83BrO4 + 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
2
O

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.[9]

See also[edit]

References[edit]

  1. ^ Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. p. 439. ISBN 0-12-352651-5. 
  2. ^ a b c d 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. ^ a b 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.  edit
  5. ^ a b Appelman, E. H. (1968). "Synthesis of perbromates". Journal of the American Chemical Society 90 (7): 1900–1901. doi:10.1021/ja01009a040.  edit
  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. ^ a b Appelman, E. H. (1969). "Perbromic acid and perbromates: synthesis and some properties". Inorg. Chem. 8 (2): 223–227. doi:10.1021/ic50072a008.  edit
  9. ^ http://pubs.acs.org/doi/abs/10.1021/ic201329q