Aluminium iodide
Chemical compound
From Wikipedia, the free encyclopedia
Aluminium iodide is the inorganic compound with the composition AlI3. It also exists a various hydrates formed by exposure of the anhydrous material to water.[4] For example the hexahydrate is obtained from a reaction between metallic aluminum or aluminum hydroxide with hydroiodic acid. Like the related chloride and bromide, AlI
3 is a strong Lewis acid and will absorb water from the atmosphere. It is employed as a reagent for the scission of certain kinds of C-O and N-O bonds. It cleaves aryl ethers and deoxygenates epoxides.[5]
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Aluminium iodide | |||
| Other names
Aluminium(III) iodide Aluminum iodide | |||
| Identifiers | |||
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3D model (JSmol) |
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| ChemSpider |
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| ECHA InfoCard | 100.029.140 | ||
| EC Number |
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PubChem CID |
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| UNII |
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| UN number | UN 3260 | ||
CompTox Dashboard (EPA) |
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| Properties | |||
| AlI3, AlI3·6H2O (hexahydrate) | |||
| Molar mass | 407.695 g/mol (anhydrous) 515.786 g/mol (hexahydrate)[1] | ||
| Appearance | white (anhydrous) or yellow powder (hexahydrate)[1] | ||
| Density | 3.98 g/cm3 (anhydrous)[1] 2.63 g/cm3 (hexahydrate)[2] | ||
| Melting point | 188.28 °C (370.90 °F; 461.43 K) (anhydrous) 185 °C, decomposes (hexahydrate)[1][2] | ||
| Boiling point | 382 °C (720 °F; 655 K) anhydrous, sublimes[1] | ||
| very soluble, partial hydrolysis | |||
| Solubility in alcohol, ether | soluble (hexahydrate) | ||
| Structure[3] | |||
| Monoclinic, mP16 | |||
| P21/c, No. 14 | |||
a = 1.1958 nm, b = 0.6128 nm, c = 1.8307 nm α = 90°, β = 90°, γ = 90° | |||
Formula units (Z) |
8 | ||
| Thermochemistry[1] | |||
Heat capacity (C) |
98.7 J/(mol·K) | ||
Std molar entropy (S⦵298) |
195.9 J/(mol·K) | ||
Std enthalpy of formation (ΔfH⦵298) |
−302.9 kJ/mol | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation
Structure
Solid AlI
3 is dimeric, consisting of Al
2I
6, similar to that of AlBr
3.[3] The structure of monomeric and dimeric forms have been characterized in the gas phase.[7] The monomer, AlI
3, is trigonal planar with a bond length of 2.448(6) Å, and the bridged dimer, Al
2I
6, at 430 K is a similar to Al
2Cl
6 and Al
2Br
6 with Al−I bond lengths of 2.456(6) Å (terminal) and 2.670(8) Å (bridging). The dimer is described as floppy with an equilibrium geometry of D2h.
Aluminium(I) iodide
The name "aluminium iodide" is widely assumed to describe the triiodide or its dimer. In fact, a monoiodide also enjoys a role in the Al–I system, although the compound AlI is unstable at room temperature relative to the triiodide:[8]
- 3 AlI → AlI3 + 2 Al
An illustrative derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al
4I
4(NEt
3)
4.
