Calcium bromide is the name for compounds with the chemical formula CaBr2(H2O)x. Individual compounds include the anhydrous material (x = 0), the hexahydrate (x = 6), and the rare dihydrate (x = 2). All are white powders that dissolve in water, and from these solutions crystallizes the hexahydrate. The hydrated form is mainly used in some drilling fluids.[1]

Synthesis, structure, and reactions

It is produced by the reaction of calcium oxide, calcium carbonate with bromine in the presence of a reducing agent such as formic acid or formaldehyde:[1]

CaO + Br2 + HCO2H → CaBr2 + H2O + CO2

Solid calcium bromide adopts the rutile structure, featuring octahedral Ca2+ centres bound to six bromide anions, which also bridge to other Ca2+ centres.

When strongly heated in air, calcium bromide reacts with oxygen to produce calcium oxide and bromine:

2 CaBr2 + O2 → 2 CaO + 2 Br2

Uses

It is mainly used as dense aqueous solutions for drilling fluids.[1] It is also used in neuroses medication, freezing mixtures, food preservatives, photography and fire retardants.[2]

It minimizes the emission of gaseous mercury in the combustion of coal.[1]

In the laboratory

Calcium bromide forms complexes with triphenylphosphine oxide, allowing for removal of triphenylphosphine oxide from reaction mixtures without the use of chromatography.[3]

References

  1. ^ a b c d Yoffe, David; Frim, Ron; Ukeles, Shmuel D.; Dagani, Michael J.; Barda, Henry J.; Benya, Theodore J.; Sanders, David C. (2013). "Bromine Compounds". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–31. doi:10.1002/14356007.a04_405.pub2. ISBN 978-3-527-30385-4.
  2. ^ "Chemical Land 21". Retrieved 25 December 2008.
  3. ^ Rodríguez Hergueta, Antonio (2022). "Easy Removal of Triphenylphosphine Oxide from Reaction Mixtures by Precipitation with CaBr2". Organic Process Research & Development. 26 (6): 1845–1853. doi:10.1021/acs.oprd.2c00104. S2CID 249558328.

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