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]
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| Names | |
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| IUPAC name
Calcium bromide
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| Other names
Calcium dibromide
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| Identifiers | |
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| ECHA InfoCard | 100.029.240 |
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| Properties | |
| CaBr2 | |
| Molar mass | 199.89 g/mol (anhydrous) 235.98 g/mol (dihydrate) |
| Appearance | anhydrous is hygroscopic colorless crystals sharp saline taste |
| Density | 3.353 g/cm3 |
| Melting point | 730 °C (1,350 °F; 1,000 K) |
| Boiling point | 1,815 °C (3,299 °F; 2,088 K) (anhydrous) 810 °C (dihydrate) |
| 125 g/100 mL (0 °C) 143 g/100 mL (20 °C) 312 g/100 mL (100 °C) | |
| Solubility in alcohol, acetone | soluble |
| Acidity (pKa) | 9 |
| -73.8·10−6 cm3/mol | |
| Structure | |
| rhomboid | |
| Thermochemistry | |
Heat capacity (C)
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75 J/mol K |
Std molar
entropy (S⦵298) |
130 J/mol K |
Std enthalpy of
formation (ΔfH⦵298) |
-647.9 kJ/mol |
Gibbs free energy (ΔfG⦵)
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-656.1 kJ/mol |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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4100 mg/kg (rat, oral) 1580 mg/kg (mouse, subcutaneous) |
| Related compounds | |
Other anions
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Calcium fluoride Calcium chloride Calcium iodide |
Other cations
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Beryllium bromide Magnesium bromide Strontium bromide Barium bromide Radium bromide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis, structure, and reactions
editIt 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
editIt 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
editCalcium bromide forms complexes with triphenylphosphine oxide, allowing for removal of triphenylphosphine oxide from reaction mixtures without the use of chromatography.[3]
References
edit- ^ 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.
- ^ "Chemical Land 21". Retrieved 25 December 2008.
- ^ 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.