Magnesium bromide explained

Magnesium bromide are inorganic compounds with the chemical formula, 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.^{[1] [2]}

Synthesis

Magnesium bromide can be synthesized by treating magnesium oxide (and related basic salts) with hydrobromic acid.^[2] It can also be made by reacting magnesium carbonate and hydrobromic acids, and collecting the solid left after evaporation.^[1]

As suggested by its easy conversion to various hydrates, anhydrous is a Lewis acid. In the coordination polymer with the formula MgBr₂(dioxane)₂, Mg²⁺ adopts an octahedral geometry.^[3]

Uses and reactions

Magnesium bromide is used as a Lewis acid catalyst in some organic synthesis, e.g., in aldol reaction.^[4]

Magnesium bromide also has been used as a tranquilizer^[1] and as an anticonvulsant for treatment of nervous disorders.^[5]

Magnesium bromide modifies the catalytic properties of palladium on charcoal.^[6]

Magnesium bromide hexahydrate has properties as a flame retardant.^[7]

Treatment of magnesium bromide with chlorine gives magnesium chloride. This reaction is employed in the production of magnesium chloride from brines.^[8]

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.^[9]

Notes and References

1. Gruyter, W. Concise Encyclopedia Chemistry, Walter de Gruyter & Company: Berlin, 1993; 612
2. Lewis, R.J. Hawley’s Condensed Chemical Dictionary, 15th ed.; John Wiley & Sons Inc.:New York, 2007; 777
3. 10.1002/chem.201903120. Structure–Solubility Relationship of 1,4-Dioxane Complexes of Di(hydrocarbyl)magnesium . 2019 . Fischer . Reinald . Görls . Helmar . Meisinger . Philippe R. . Suxdorf . Regina . Westerhausen . Matthias . Chemistry – A European Journal . 25 . 55 . 12830–12841 . 31328293 . 7027550 .
4. 10.1021/ja0119548. Diastereoselective Magnesium Halide-Catalyzed anti-Aldol Reactions of Chiral N-Acyloxazolidinones . 2002 . Evans . David A. . Tedrow . Jason S. . Shaw . Jared T. . Downey . C. Wade . Journal of the American Chemical Society . 124 . 3 . 392–393 . 11792206 .
5. Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002,
6. 10.1021/ol020032m. Magnesium Bromide Mediated Highly Diastereoselective Heterogeneous Hydrogenation of Olefins. 2002. Bouzide. Abderrahim. Organic Letters. 4. 1347–50. 11950359. 8.
7. 10.1007/s10973-007-8928-4. XRD characterization of the ashes from a burned cellulosic fabric impregnated with magnesium bromide hexahydrate as flame-retardant. 2008. Mostashari. S. M.. Fayyaz. F.. Journal of Thermal Analysis and Calorimetry. 92. 3. 845. 94416902.
8. Book: 10.1002/14356007.a15_595 . Magnesium Compounds . Ullmann's Encyclopedia of Industrial Chemistry . 2000 . Seeger . Margarete . Otto . Walter . Flick . Wilhelm . Bickelhaupt . Friedrich . Akkerman . Otto S. . 3-527-30673-0 .
9. 10.1107/S0108270113028138 . Crystal Structures of Hydrates of Simple Inorganic Salts. I. Water-Rich Magnesium Halide Hydrates MgCl₂·8H₂O, MgCl₂·12H₂O, MgBr₂·6H₂O, MgBr₂·9H₂O, MgI₂·8H₂O and MgI₂·9H₂O . 2013 . Hennings . Erik . Schmidt . Horst . Voigt . Wolfgang . Acta Crystallographica Section C Crystal Structure Communications . 69 . 11 . 1292–1300 . 24192174 .