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Magnesium iodide

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Title: Magnesium iodide  
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Subject: Magnesium hydride, Magnesium bromide, Magnesium phosphate, Dimagnesium phosphate, Magnesium benzoate
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Magnesium iodide

Magnesium iodide
CAS number  YesY,  (anhydrous)
75535-11-4 (hexahydrate)
7790-31-0 (octahydrate)
ChemSpider  N
EC number
Jmol-3D images Image 1
Molecular formula 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)
Solubility in water 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
Crystal structure Hexagonal (anhydrous)
Monoclinic (hexahydrate)
Orthorhombic (octahydrate)
heat capacity
74 J/mol K
Std molar
134 J/mol K
Std enthalpy of
-364 kJ/mol
R-phrases R36 R38 R42 R43 R61
S-phrases S22 S36/37/39 S45 S53[3]
NFPA 704
Related compounds
Other anions Magnesium fluoride
Magnesium bromide
Magnesium chloride
Other cations beryllium iodide
calcium iodide
strontium iodide
barium iodide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N   YesY/N?)

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,  
  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,  
  5. ^ Wilsmore, N. T. M. (1891). James Hector, ed. "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,  
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