Magnesium bromide is a chemical compound of magnesium and bromine, with the chemical formula MgBr2. It is white and deliquescent crystalline solid. It is often used as a mild sedative and as an anticonvulsant for treatment of nervous disorders.[2] It is water-soluble and somewhat soluble in alcohol. It can be found naturally in small amounts in some minerals such as: bischofite and carnallite, and in sea water, such as that of the Dead Sea.[3][4]
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3D model (JSmol)
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ChemSpider |
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ECHA InfoCard | 100.029.246 |
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CompTox Dashboard (EPA)
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Properties | |
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Molar mass | 184.113 g/mol (anhydrous) 292.204 g/mol (hexahydrate) |
Appearance | white hygroscopic hexagonal crystals (anhydrous) colorless monoclinic crystals (hexahydrate) |
Density | 3.72 g/cm3 (anhydrous) 2.07 g/cm3 (hexahydrate) |
Melting point | 711 °C (1,312 °F; 984 K) 172.4 °C, decomposes (hexahydrate) |
Boiling point | 1,250 °C (2,280 °F; 1,520 K) |
102 g/(100 mL) (anhydrous) 316 g/(100 mL) (0 °C, hexahydrate) | |
Solubility | ethanol: 6.9 g/(100 mL) methanol: 21.8 g/(100 mL) |
−72.0·10−6 cm3/mol | |
Structure | |
Rhombohedral, hP3 | |
P-3m1, No. 164 | |
octahedral | |
Thermochemistry | |
Heat capacity (C)
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70 J/(mol·K) |
Std molar
entropy (S⦵298) |
117.2 J·mol−1·K−1 |
Std enthalpy of
formation (ΔfH⦵298) |
−524.3 kJ·mol−1 |
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NFPA 704 (fire diamond) | |
Safety data sheet (SDS) | External SDS |
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Other anions
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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Magnesium bromide can be synthesized by treating with magnesium oxide (and related basic salts) with hydrobromic acid.[4] It can also be made by reacting magnesium carbonate and hydrobromic acids, and collecting the solid left after evaporation.[3]
As suggested by its easy conversion to various hydrates, anhydrous MgBr2 is a Lewis acid. In the coordination polymer with the formula MgBr2(dioxane)2, Mg2+ adopts an octahedral geometry.[5]
Magnesium bromide is used as a Lewis acid catalyst in some organic synthesis, e.g., in aldol reaction.[6] In organosilicon chemistry, magnesium bromide forms adducts R2SiXMgBr2.[7]
Magnesium bromide also has been used as a tranquilizer.[3]
Magnesium bromide modifies the catalytic properties of palladium on charcoal.[8]
Magnesium bromide hexahydrate has properties as a flame retardant. It was found that if 0.125 mol/L of magnesium bromide hexahydrate was added to a cotton material it acted as a flame retardant.[9]