Lithium aluminium hydride
| Lithium aluminium hydride | |
|---|---|
| IUPAC name | Lithium tetrahydridoaluminate(1−) |
| Identifiers | |
| CAS number | [] |
| RTECS | BD0100000 |
| Properties | |
| Chemical formula | LiAlH4 |
| Molar mass | 37.95 g/mol |
| Appearance | white crystals (pure samples) grey powder (commercial material) hygroscopic |
| Density | 0.917 g/cm3, solid |
| Melting point |
150 °C (423 K), decomposing |
| Solubility in water | reactive |
| Structure[1] | |
| Crystal structure | monoclinic |
| Space group | P21c |
| Coordination geometry | tetrahedral (Al) |
| Hazards[2] | |
| EU index number | 001-002-00-4 |
| GHS pictograms | 
|
| GHS signal word | DANGER |
| GHS hazard statements | H260 |
| Related compounds | |
| Other hydride | aluminium hydride sodium borohydride sodium hydride |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Lithium aluminium hydride, LiAlH4, often abbreviated to LAH or "Lithal", is the lithium salt of the tetrahydridoaluminate(1−) anion. A moderately air-stable white or grey solid, it is widely used as a strong reducing agent in organic synthesis.
It was first prepared from the reaction between lithium hydride (LiH) and aluminium chloride:[3]
- 4 LiH + AlCl3 → LiAlH4 + 3 LiCl
In addition to this method, the industrial synthesis entails the initial preparation of sodium aluminium hydride from the elements under high pressure and temperature:[4]
- Na + Al + 2 H2 → NaAlH4
LAH is then prepared by metathesis reaction according to:
- NaAlH4 + LiCl → LiAlH4 + NaCl
which proceeds in a high yield of LAH. LiCl is removed by filtration from an ethereal solution of LAH, with subsequent precipitation of LAH to yield a product containing around 1% w/w LiCl.[4]
References
- ↑ Løvvik, O. M.; Opalka, Susanne M.; Brinks, Hendrik W.; Hauback, Bjørn C. Crystal structure and thermodynamic stability of the lithium alanates LiAlH4 and Li3AlH6. Phys. Rev. B 2004, 69 (13), 134117. DOI: 10.1103/PhysRevB.69.134117.
- ↑ Index no. 001-002-00-4 of Annex VI, Part 3, to Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC and 1999/45/EC, and amending Regulation (EC) No 1907/2006. OJEU L353, 31.12.2008, pp 1–1355 at p 340.
- ↑ Finholt, A. E.; Bond, A. C.; Schlesinger, H. I. Lithium Aluminum Hydride, Aluminum Hydride and Lithium Gallium Hydride, and Some of their Applications in Organic and Inorganic Chemistry. J. Am. Chem. Soc. 1947, 69 (5), 1199–1203. DOI: 10.1021/ja01197a061.
- ↑ 4.0 4.1 Holleman, A. F.; Wiberg, E.; Wiberg, N. Lehrbuch der Anorganischen Chemie, 102nd ed.; de Gruyter, 2007. ISBN 978-3-11-017770-1.
External links
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See also the corresponding article on Wikipedia. |
