Magnesium bromide

Magnesium bromide is a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 of magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 and bromine

Bromine

Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

 that is white and deliquescent. It is often used as a mild sedative

Sedative

A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....

 and as an anticonvulsant

Anticonvulsant

The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...

 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

Bischofite is a hydrous magnesium chloride mineral with formula MgCl2·6. It belongs to halides and is a sea salt concentrate dated from the Permian Period...

 and carnallite

Carnallite

Carnallite is an evaporite mineral, a hydrated potassium magnesium chloride with formula: KMgCl3·6. It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare pseudohexagonal orthorhombic crystals...

, and in sea water, such as that of the Dead Sea

Dead Sea

The Dead Sea , also called the Salt Sea, is a salt lake bordering Jordan to the east and Israel and the West Bank to the west. Its surface and shores are below sea level, the lowest elevation on the Earth's surface. The Dead Sea is deep, the deepest hypersaline lake in the world...

.

Synthesis

Magnesium bromide can be synthesized by reacting hydrobromic acid

Hydrobromic acid

Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at 124.3 °C and contains 47.6% HBr by weight, which is 8.89 mol/L. Hydrobromic acid has a pKa of −9, making it a...

 with magnesium oxide

Magnesium oxide

Magnesium oxide , or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of and consists of a lattice of Mg2+ ions and O2– ions held together by ionic bonds...

 and crystallizing the product. It can also be made by reacting magnesium carbonate and hydrobromic acid, and collecting the solid left after evaporation.

An alternative route is adding magnesium to a solution of liquid ammonia

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 and sodium bromide

Sodium bromide

Sodium bromide is an inorganic compound with the formula NaBr. It is a high-melting white, crystalline solid that resembles sodium chloride. It is a widely used source of the bromide ion and has many applications.-Synthesis, structure, reactions:...

, then evaporating the solvent off and collecting the precipitate.

Uses

Magnesium bromide is used at a catalyst for many reactions, typically as a solvent or used as a Grignard reagent. The first being a solvent free one pot synthesis of dihydropyrimidinones which are used most often in the pharmaceutical world. Dihydropyrimidinones are used in medications such as calcium channel blockers, and HIVgp-120-CD4 inhibitors. It also has been used as a tranquilizer. Magnesium bromide in combination with CH₂Cl₂ catalyzes a reaction that causes specific symmetry and chiral centers through hydrogenation of olefins. Magnesium bromide when bonded to other functional groups has shown more practical uses other than catalyzing reactions. When bonded to an ethyl group it is used for regiospecific analysis of triglycerols. Magnesium bromide hexahydrate is being worked with to be used 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. Magnesium bromide was used to synthesize the first stable magnesium silylenoid

Silylenoid

A Silylenoid in organosilicon chemistry is a type of chemical compound with the general structure R2SiXM where R is any organic residue, X a halogen and M a metal. Silylenoids are the silicon pendants of carbenoid and both compounds have carbene or silylene like properties.Silylenoids are...

. A silylenoid is a compound that contains R₂SiM_X (M is metal and R is an organic moiety). Traditionally only lithium

Lithium

Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

, potassium

Potassium

Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

, and sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

could be used. The magnesium silylenoid is synthesized through the addition of magnesium bromide to lithium lithium methyl bromosilylenoid. The magnesium atom replaces the lithium in the complex and has a bromide attached to it. This complex is stable at room temperature.