Aluminium iodide
Encyclopedia : A : AL : ALU : Aluminium iodide
| Aluminum iodide | |
|---|---|
|
| |
| General | |
| Other names | Aluminium(III) iodide Aluminum triiodide |
| Molecular formula | AlI3 |
| Molar mass | 407.695 |
| Appearance | colorless powder but impure samples are often brown |
| CAS number | [7784-23-8] |
| Properties | |
| Density and phase | 3.98 g/cm3, solid |
| Solubility | decomposes in water, alcohols soluble in carbon disulfide |
| Melting point | 191 °C |
| Boiling point | 360 °C |
| Vapour Pressure | 1 mm at 178 °C |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
Aluminium iodide is any chemical compound containing only aluminium and iodine. Invariably, the name refers to a compound of the composition AlI3, formed by the reaction of aluminium and iodineG. W. Watt, J. L. Hall "Aluminum Iodide" Inorganic Syntheses, 1953, Volume IV, pages 117-119 or the action of HI on Al metal. As for the related chloride and bromide, AlI3 is a strong Lewis acid and should be protected from the atmosphere.
Monomer-dimer equilibrium
Like the corresponding tribromide, solid aluminium triiodide exists as the dimer Al2I6, consisting of tetrahedrally coordinated Al centers. In contrast, aluminium trichloride features six-coordinate Al in the solid state, adopting the bitetrahedral structure only upon melting or evaporation. One can appreciate that the names of these halides do not indicate the "molecularity" of the parent compounds, i.e. whether they are monomers or dimers.The dimeric Al2I6 structure (C2v point group symmetry) persists in solution (in the absence of Lewis bases) and in the gas phase, at least at low temperatures. At high temperatures, gaseous Al2I6 dissociates:Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4.
- Al2I6 → 2 AlI3 ΔH°diss = 50 kJ/mol
- Al2Br6 → 2 AlBr3 ΔH°diss = 59 kJ/mol
Applications in Aluminum iodide is employed to break certain kinds of C-O and N-O bonds. It cleaves aryl ethers and deoxygenates epoxides.M. Gugelchuk "Aluminum Iodide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
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 composition AlI is unstable at room temperature with respect to the triiodide“Aluminum(I) and Gallium(I) Compounds: Syntheses, Structures, and Reactions” Dohmeier, C.; Loos, D.; Schnöckel, H. Angewandte Chemie International Edition in English (1996) Volume 35, Pages 129 - 149.- 6 AlI → Al2I6 + 4 Al
Safety
Hydrolysis aluminum triiodide will release some HI, which is corrosive. Lewis acids are skin irritants.References
External links
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.