Magnesium bromide

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Magnesium bromide

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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	Template:Chembox CalcTemperatures
Boiling point	Template:Chembox CalcTemperatures
Solubility	ethanol: 6.9 g/(100 mL) methanol: 21.8 g/(100 mL)
Template:Longitem	−72.0·10−6 cm3/mol
Template:Longitem	Rhombohedral, hP3
Template:Longitem	P-3m1, No. 164
Template:Longitem	octahedral
Template:Longitem	70 J/(mol·K)
Template:Longitem	117.2 J/(mol·K)
Template:Longitem	−524.3 kJ/mol
NFPA 704 (fire diamond)	Template:NFPA 704 diamond
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Magnesium bromide are inorganic compounds with the chemical formula Template:Chem2, where x can range from 0 to 9. They are all white deliquescent solids. Some magnesium bromides have been found naturally as rare minerals such as: bischofite and carnallite.

Synthesis

Magnesium bromide can be synthesized by treating magnesium oxide (and related basic salts) with hydrobromic acid. It can also be made by reacting magnesium carbonate and hydrobromic acids, and collecting the solid left after evaporation.

As suggested by its easy conversion to various hydrates, anhydrous Template:Chem2 is a Lewis acid. In the coordination polymer with the formula MgBr₂(dioxane)₂, Mg²⁺ adopts an octahedral geometry.

Uses and reactions

Magnesium bromide is used as a Lewis acid catalyst in some organic synthesis, e.g., in aldol reaction.

Magnesium bromide also has been used as a tranquilizer and as an anticonvulsant for treatment of nervous disorders.

Magnesium bromide modifies the catalytic properties of palladium on charcoal.

Magnesium bromide hexahydrate has properties as a flame retardant.

Treatment of magnesium bromide with chlorine gives magnesium chloride. This reaction is employed in the production of magnesium chloride from brines.

Structure

Two hydrates are known, the hexahydrate and the nonahydrate. Several reports claim a decahydrate, but X-ray crystallography confirmed that it is a nonahydrate. The hydrates feature [Mg(H₂O)₆]²⁺ ions.<ref></ref it can also cause violently convulsing and potential release of bowels