Magnesium iodide

Chemical compound From Wikipedia, the free encyclopedia

Magnesium iodide is an inorganic compound with the chemical formula MgI2. It forms various hydrates MgI2·xH2O. Magnesium iodide is a salt of magnesium and hydrogen iodide. These salts are typical ionic halides, being highly soluble in water.

Quick facts Names, Identifiers ...
Magnesium iodide
Names
IUPAC name
Magnesium iodide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.738 Edit this at Wikidata
EC Number
  • 233-825-1
UNII
  • InChI=1S/2HI.Mg/h2*1H;/q;;+2/p-2 ☒N
    Key: BLQJIBCZHWBKSL-UHFFFAOYSA-L ☒N
  • InChI=1/2HI.Mg/h2*1H;/q;;+2/p-2
    Key: BLQJIBCZHWBKSL-NUQVWONBAV
  • I[Mg]I
  • [Mg+2].[I-].[I-]
Properties
  • MgI2 (anhydrous)
  • MgI2·6H2O (hexahydrate)
  • MgI2·8H2O (octahydrate)[1]
Molar mass
  • 278.1139 g/mol (anhydrous)
  • 386.2005 g/mol (hexahydrate)
  • 422.236 g/mol (octahydrate)
Appearance white crystalline solid
Odor odorless
Density
  • 4.43 g/cm3 (anhydrous solid)
  • 2.353 g/cm3 (hexahydrate solid)
  • 2.098 g/cm3 (octahydrate solid)
Melting point 637 °C (1,179 °F; 910 K) (anhydrous, decomposes)
41 °C (octahydrate, decomposes)
  • 54.7 g/(100 cm3) (anhydrous, 0 °C)
  • 148 g/(100 cm3) (anhydrous, 18 °C)[2]
  • 81 g/(100 cm3) (octahydrate, 20 °C)
Solubility soluble in ether, alcohol and ammonia
−111.0·10−6 cm3/mol
Structure
Thermochemistry
74 J/(mol·K)
134 J/(mol·K)
−364 kJ/mol
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard COR: Corrosive; strong acid or base. E.g. sulfuric acid, potassium hydroxide
3
1
1
COR
Related compounds
Other anions
Other cations
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Uses

Magnesium iodide has few commercial uses, but can be used to prepare compounds for organic synthesis.

Preparation

Magnesium iodide can be prepared from magnesium oxide, magnesium hydroxide, and magnesium carbonate by treatment with hydroiodic acid:[3]

MgO + 2 HI → MgI2 + H2O
Mg(OH)2 + 2 HI → MgI2 + 2 H2O
MgCO3 + 2 HI → MgI2 + CO2 + H2O

Reactions

Magnesium iodide is stable at high heat under a hydrogen atmosphere, but decomposes in air at normal temperatures, turning brown from the release of elemental iodine. When heated in air, it decomposes completely to magnesium oxide.[4]

Another method to prepare MgI2 is mixing powdered elemental iodine and magnesium metal. In order to obtain anhydrous MgI2, the reaction should be conducted in a strictly anhydrous atmosphere; dry-diethyl ether can be used as a solvent.

Usage of magnesium iodide in the Baylis-Hillman reaction tends to give (Z)-vinyl compounds.[5]

Demethylation of certain aromatic methyl ethers can be afforded using magnesium iodide in diethyl ether.[6]

Hydrates

Two hydrates are known, the octahydrate and the nonahydrate, both verified by X-ray crystallography These hydrates feature [Mg(H2O)6]2+ ions.[7]

References

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