Magnesium iodide

Magnesium iodide

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Names
IUPAC name Magnesium iodide
Identifiers
CAS Number	10377-58-9 (anhydrous) Y 75535-11-4 (hexahydrate) N 7790-31-0 (octahydrate) N
ChemSpider	59700 N
EC Number	233-825-1
Jmol 3D model	Interactive image
PubChem	66322
InChI 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
SMILES [Mg+2].[I-].[I-]
Properties
Chemical formula	MgI2 (anhydrous) MgI2.6H2O (hexahydrate) MgI2.8H2O (octahydrate)
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) 81 g/100 cm3 (octahydrate, 20 °C)
Solubility	soluble in ether, alcohol and ammonia
Structure
Crystal structure	Hexagonal (anhydrous) Monoclinic (hexahydrate) Orthorhombic (octahydrate)
Thermochemistry
Specific heat capacity (C)	74 J/mol K
Std molar entropy (So298)	134 J/mol K
Std enthalpy of formation (ΔfHo298)	-364 kJ/mol
Vapor pressure	{{{value}}}
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.

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:

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.

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.