Lithium aluminium hydride
| Lithium aluminium hydride | |
|---|---|
| IUPAC name | Lithium tetrahydridoaluminate(1−) |
| Identifiers | |
| InChI | InChI=1/Al.Li.4H/q-1;+1;;;;/rAlH4.Li/h1H4;/q-1;+1 |
| InChIKey | OCZDCIYGECBNKL-PDCCDREHAZ |
| Standard InChI | InChI=1S/Al.Li.4H/q-1;+1;;;; |
| Standard InChIKey | OCZDCIYGECBNKL-UHFFFAOYSA-N |
| CAS number | [] |
| EC number | |
| RTECS | BD0100000 |
| ChemSpider | |
| Properties[1] | |
| Chemical formula | LiAlH4 |
| Molar mass | 37.954 g mol–1 |
| Appearance | white or grey solid |
| Density | 0.917 g cm–3 |
| Melting point |
125 °C decomp. |
| Solubility in water | reacts |
| Solubility in diethyl ether | approx. 300 g dm–3 |
| Structure[2] | |
| Crystal structure | monoclinic |
| Space group | P21/c |
| Coordination geometry | tetrahedral (Al) |
| Thermochemistry[3][4] | |
| Std enthalpy of formation ΔfH |
–117.15 kJ mol–1 |
| Standard molar entropy S |
87.90 J K–1 mol–1 |
| Hazards[5] | |
| EU index number | 001-002-00-4 |
| GHS pictograms | 
|
| GHS signal word | DANGER |
| GHS hazard statements | H260 |
| Related compounds | |
| Other hydrides | 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:[6]
- 4 LiH + AlCl3 → LiAlH4 + 3 LiCl
The modern industrial synthesis involves the initial preparation of sodium aluminium hydride from the elements under high pressure and temperature:[7]
- 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. Lithium chloride is removed by filtration from an ethereal solution of LAH, with subsequent precipitation of LAH to yield a product containing around 1% LiCl by mass.[7]
References
- ↑ CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p B-113. ISBN 0-8493-0462-8.
- ↑ 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.
- ↑ Lithium tetrahydroaluminate. In NIST Chemistry WebBook; National Institute for Standards and Technology, <http://webbook.nist.gov/cgi/inchi/InChI%3D1S/Al.Li.4H/q-1;+1;;;;>. (accessed 20 June 2010).
- ↑ Smith, Martin B.; Bass, George E., Jr. Heats and Free Energies of Formation of the Alkali Aluminum Hydrides and of Cesium Hydride. J. Chem. Eng. Data 1963, 8 (3), 342–46. DOI: 10.1021/je60018a020.
- ↑ 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.
- ↑ 7.0 7.1 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. |
