Magnesium iodide

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Magnesium iodide
IUPAC name
Magnesium iodide
3D model (JSmol)
ECHA InfoCard 100.030.738
EC Number 233-825-1
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
Hexagonal (anhydrous)
Monoclinic (hexahydrate)
Orthorhombic (octahydrate)
74 J/mol K
134 J/mol K
-364 kJ/mol
R-phrases (outdated) R36 R38 R42 R43 R61
S-phrases (outdated) S22 S36/37/39 S45 S53[3]
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Other anions
Magnesium fluoride
Magnesium bromide
Magnesium chloride
Other cations
beryllium iodide
calcium iodide
strontium iodide
barium iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Magnesium iodide is the name for the chemical compounds with the formulas MgI2 and its various hydrates MgI2(H2O)x. These salts are typical ionic halides, being highly soluble in water.


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


Magnesium iodide can be prepared from magnesium oxide, magnesium hydroxide, and magnesium carbonate by treatment with hydroiodic acid:[4]

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


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.[5]

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

Usage of magnesium iodide in the Baylis-Hillman reaction tends to give (Z)-vinyl compounds.[6]


  1. ^ Perry, Dale L.; Phillips, Sidney L. (1995), Handbook of Inorganic Compounds, CRC Press, p. 240, ISBN 0-8493-8671-3, retrieved 2007-12-09 
  2. ^ Magnesium Iodide MSDS at AlfaAesar
  3. ^ Safety (MSDS) data for magnesium iodide
  4. ^ Patnaik, Pradyot (2003), Handbook of Inorganic Chemicals, McGraw-Hill Professional, pp. 527–528, ISBN 0-07-049439-8, retrieved 2007-12-09 
  5. ^ Wilsmore, N. T. M. (1891). "Note on Magnesium Iodide". In James Hector. Report of the Third Meeting of the Australasian Association for the Advancement of Science. Sydney: The Association. p. 116. Retrieved 2007-12-09. 
  6. ^ Tietze, Lutz-Friedjan; Brasche, Gordon; Gericke, Kersten (2006), Domino Reactions in Organic Synthesis, Wiley-VCH, p. 59, ISBN 3-527-29060-5, retrieved 2007-12-09