Magnesium iodide

Magnesium iodide
IUPAC name Magnesium iodide
Identifiers
CAS number	10377-58-9 Y,  (anhydrous) 75535-11-4 (hexahydrate) 7790-31-0 (octahydrate)
PubChem	66322
Properties
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 (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
Structure
Crystal structure	Hexagonal (anhydrous) Monoclinic (hexahydrate) Orthorhombic (octahydrate)
Hazards
R-phrases	R36 R38 R42 R43 R61
S-phrases	S22 S36/37/39 S45 S53[3]
NFPA 704	1 3 1
Related compounds
Other anions	Magnesium fluoride Magnesium bromide Magnesium chloride
Other cations	beryllium iodide calcium iodide strontium iodide barium iodide
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.

Reactions

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 powder and then adding few drops of water on it. Both of these reactants should be extremely dry, otherwise they'll start to reacting immediately before the water is added. This reaction is very violent and produces a large quantity of toxic purple iodine vapor.

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

References

1. ^ Perry, Dale L.; Phillips, Sidney L. (1995), Handbook of Inorganic Compounds, CRC Press, pp. 240, ISBN 0849386713, http://books.google.com/?id=0fT4wfhF1AsC&pg=PA240&dq=%22magnesium+iodide%22, 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 0070494398, http://books.google.com/?id=Xqj-TTzkvTEC&pg=RA1-PA527&dq=%22magnesium+iodide%22, 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. pp. 116. http://books.google.com/books?id=ktw4AAAAMAAJ&pg=PA116&dq=%22magnesium+iodide%22&as_brr=3&ei=yTVcR9qLNYHciwHVg-maAw&ie=ISO-8859-1#PPA116,M1. Retrieved 2007-12-09. 
6. ^ Tietze, Lutz-Friedjan; Brasche, Gordon; Gericke, Kersten (2006), Domino Reactions in Organic Synthesis, Wiley-VCH, pp. 59, ISBN 3527290605, http://books.google.com/?id=qijhLyZ6SokC&pg=PA59&dq=%22magnesium+iodide%22+reactions, retrieved 2007-12-09