Magnesium bromide is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

and

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

, with the chemical formula . It is white and

deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

crystalline solid. It is often used as a mild sedative and as an anticonvulsant for treatment of nervous disorders. It is water-soluble and somewhat soluble in alcohol. It can be found naturally in small amounts in some minerals such as:

bischofite Bischofite is a hydrous magnesium chloride mineral with formula MgCl2·6H2O. It belongs to halides and is a sea salt concentrate. It contains many macro- and micro-elements vital for human health, in much higher concentrations than can be found ...

and

carnallite Carnallite (also carnalite) is an evaporite mineral, a hydrated potassium magnesium chloride with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare ...

, and in sea water, such as that of the Dead Sea.Gruyter, W. Concise Encyclopedia Chemistry, Walter de Gruyter & Company: Berlin, 1993; 612Lewis, R.J. Hawley’s Condensed Chemical Dictionary, 15th ed.; John Wiley &Sons Inc.:New York, 2007; 777

Synthesis

Magnesium bromide can be synthesized by treating with

magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...

(and related basic salts) with

hydrobromic acid Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains 47.6% HBr by mass, which is 8.77 mol/L. ...

. 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 In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

, anhydrous is a Lewis acid. In the coordination polymer with the formula MgBr₂(dioxane)₂, Mg²⁺ adopts an octahedral geometry.

Uses

Magnesium bromide is used as a Lewis acid

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

in some organic synthesis, e.g., in

aldol reaction The aldol reaction is a means of forming carbon–carbon bonds in organic chemistry. Discovered independently by the Russian chemist Alexander Borodin in 1869 and by the French chemist Charles-Adolphe Wurtz in 1872, the reaction combines two c ...

. In

organosilicon chemistry Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordinary organic c ...

, magnesium bromide forms adducts . Magnesium bromide also has been used as a tranquilizer. Magnesium bromide modifies the catalytic properties of palladium on charcoal. 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.

References

{{bromine compounds Bromides Magnesium compounds Alkaline earth metal halides