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Magnesium iodide

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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)
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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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.

Uses

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

Preparation

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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

[edit]

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

[edit]

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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  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[permanent dead link]
  3. ^ Patnaik, Pradyot (2003), Handbook of Inorganic Chemicals, McGraw-Hill Professional, pp. 527–528, ISBN 0-07-049439-8, retrieved 2007-12-09
  4. ^ Wilsmore, N. T. M. (1891). "Note on Magnesium Iodide". In 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.
  5. ^ Tietze, Lutz-Friedjan; Brasche, Gordon; Gericke, Kersten (2006), "Domino Reactions in Organic Synthesis", Chemical Reviews, 96 (1), Wiley-VCH: 115–136, doi:10.1021/cr950027e, ISBN 3-527-29060-5, PMID 11848746, retrieved 2007-12-09
  6. ^ Yamaguchi, Seiji; Nedachi, Masahiro; Yokoyama, Hajime; Hirai, Yoshiro (October 1999). "Regioselective demethylation of 2,6-dimethoxybenzaldehydes with magnesium iodide etherate". Tetrahedron Letters. 40 (41): 7363–7365. doi:10.1016/S0040-4039(99)01411-2.
  7. ^ Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang (2013). "Crystal Structures of Hydrates of Simple Inorganic Salts. I. Water-Rich Magnesium Halide Hydrates MgCl2·8H2O, MgCl2·12H2O, MgBr2·6H2O, MgBr2·9H2O, MgI2·8H2O and MgI2·9H2O". Acta Crystallographica Section C Crystal Structure Communications. 69 (11): 1292–1300. doi:10.1107/S0108270113028138. PMID 24192174.