Overview
Magnesium nitrate Mg (NO3)2 are colorless hygroscopic crystals. The solubility in water at 20 ° C is 73.3 g per 100 g. Hexahydrate crystallizes from aqueous solutions. Above 90 ° C, it is dehydrated to monohydrate. Then, water is split off with partial hydrolysis BetaCALM decomposition to magnesium oxide. This process is used in the synthesis of high purity magnesium oxide. Nitrates of other metals, as well as various magnesium compounds, are obtained from magnesium nitrate. In addition, magnesium nitrate is part of complex fertilizers and pyrotechnic mixtures.
best way Perchlorate Mg (ClO
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2 forms very hygroscopic colorless crystals. It is soluble BetaCALM water (99.6 g per 100 g) and organic solvents. Hexahydrate crystallizes from aqueous solutions. Concentrated solutions of magnesium perchlorate in organic solvents and its solvates with reductant molecules are explosive.
Partially hydrated magnesium perchlorate, containing 2–2.5 water molecules, is marketed under the commercial name “Anhydrone”. To obtain anhydrous magnesium perchlorate, it is dried in vacuum at 200–300 ° C. It is used as a gas desiccant. It absorbs not only water vapor, but also ammonia, vapors of alcohols, acetone and other polar substances.
Magnesium perchlorate is used as an acylation catalyst according to the Friedel-Crafts reaction, and also as an oxidizing agent in microanalysis.
Magnesium fluoride MgF2 slightly soluble in water (0.013 g per 100 g at 25 ° C). It is found in nature in the form of the mineral selaite. Magnesium fluoride is prepared by reacting magnesium sulfate or magnesium oxide with hydrofluoric acid or magnesium chloride with potassium or ammonium fluoride.
Magnesium fluoride is a part of fluxes, glasses, ceramics, enamels, catalysts, mixtures for producing artificial mica and asbestos. In addition, it is an optical and laser material.
Magnesium chloride MgCl2 is one of the most industrially important salts of magnesium. Its solubility is 54.5 g per 100 g of water at 20 ° C. Concentrated aqueous solutions of magnesium chloride dissolve magnesium oxide. MgCl crystallizes from the resulting solutions2MMg (OH)2NH2O. These compounds are part of magnesia cements.
Magnesium chloride forms crystalline hydrates with 1, 2, 4, 6, 8, and 12 water molecules. With increasing temperature, the number of water of crystallization decreases.
In nature, magnesium chloride is found in the form of bischofite minerals MgCl26H2O, Chlormagnesite MgCl2, as well as carnallite. It is found in sea water, brine of another pill lakes, some underground brines.
Anhydrous magnesium chloride is used in the production of magnesium metal and magnesium oxide, hexahydrate - to obtain magnesia cements. An aqueous solution of magnesium chloride is used as a refrigerant and antifreeze. It serves as a means against icing of the airfields of airfields, railway rails and arrows, as well as against freezing of coal and ores. A solution of magnesium chloride is impregnated with wood to make it fireproof.
Magnesium bromide MgBr2 soluble in water (101.5 g per 100 g at 20 ° C). From aqueous solutions crystallizes from –42.7 to 0.83 ° C in the form of decahydrate, and at a higher temperature, in the form of hexahydrate. It forms numerous crystalline solvates such as MgB26ROH (R = Me, Et, Pr), MgBr26Me2CO, MgBr23Et2O, as well as ammines MgBr2·nNH3 (n = 2–6).
Complex compounds of magnesium. In aqueous solutions, a magnesium ion exists in the form of an aquacomplex [Mg (H2O)6] 2+. In a non-aqueous solvent, for example in liquid ammonia, a magnesium ion forms complexes with solvent molecules. Solvates of magnesium salts usually crystallize from such solutions. Several MX type halide complexes are known.four 2–, where X is the halide anion.
Among the complex compounds of magnesium, chlorophylls, which are modified porphyrin magnesium complexes, are of particular importance. They are vital for photosynthesis in green plants.
Organomagnesium compounds. Numerous compounds containing metal – carbon bonds have been obtained for magnesium. Especially a lot of research is devoted to Grignard reagents RMgX (X = Cl, Br, I).
Grignard reagents are the most important organometallic compounds of magnesium and probably the most used organometallic reagents. This is due to the ease of their preparation and synthetic versatility. It was established that in solution these compounds can contain a variety of chemical particles in mobile equilibrium.
Grignard reagents are usually obtained by slowly adding organic halide to a suspension of magnesium chips in a suitable solvent with vigorous stirring and the complete absence of air and moisture. The reaction usually begins slowly. It can be initiated by a small iodine crystal, which destroys the protective layer on the metal surface.
Grignard reagents are widely used for the synthesis of alcohols, aldehydes, ketones, carboxylic acids, esters and amides and are probably the most important reagents for creating carbon – carbon bonds, as well as bonds between carbon atoms and other elements (nitrogen, oxygen, sulfur, etc. .d.).
