Difference between revisions of "Lithium aluminium hydride"
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| − | '''Lithium aluminium hydride''', LiAlH<sub>4</sub>, often abbreviated to '''LAH''' or "'''Lithal'''", is the [[lithium]] [[salt]] of the tetrahydridoaluminate(1−) anion. A moderately air-stable grey solid, it is widely used as a strong [[reducing agent]] in [[organic synthesis]]. | + | {{chembox |
| + | | Name = Lithium aluminium hydride | ||
| + | | IUPACName = Lithium tetrahydridoaluminate(1−) | ||
| + | | Section1 = {{Chembox Identifiers | ||
| + | | CASNo = 16853-85-3 | ||
| + | | CASNo_Ref = {{cascite}} | ||
| + | | RTECS = BD0100000 | ||
| + | }} | ||
| + | | Section2 = {{Chembox Properties | ||
| + | | Formula = LiAlH<sub>4</sub> | ||
| + | | MolarMass = 37.95 g/mol | ||
| + | | Appearance = white crystals (pure samples)<br />grey powder (commercial material) <br> [[hygroscopic]] | ||
| + | | Density = 0.917 g/cm<sup>3</sup>, solid | ||
| + | | Solubility = reactive | ||
| + | | MeltingPt = 150 °C (423 K), decomposing | ||
| + | }} | ||
| + | | Section3 = {{Chembox Structure | ||
| + | | Reference = <ref>{{citation | last1 = Løvvik | first1 = O. M. | last2 = Opalka | first2 = Susanne M. | last3 = Brinks | first3 = Hendrik W. | last4 = Hauback | first4 = Bjørn C. | title = Crystal structure and thermodynamic stability of the lithium alanates LiAlH<sub>4</sub> and Li<sub>3</sub>AlH<sub>6</sub> | year = 2004 | journal = Phys. Rev. B | volume = 69 | issue = 13 | pages = 134117 | doi = 10.1103/PhysRevB.69.134117}}.</ref> | ||
| + | | Coordination = tetrahedral (Al) | ||
| + | | CrystalStruct = [[monoclinic]] | ||
| + | | SpaceGroup = P2<sub>1</sub>c | ||
| + | }} | ||
| + | | Section7 = {{Chembox Hazards | ||
| + | | Reference = <ref>{{CLP Regulation|index=001-002-00-4|page=340}}</ref> | ||
| + | | EUIndex = 001-002-00-4 | ||
| + | | MSDS = | ||
| + | | GHSPictograms = {{GHS02|Water-react. 1}} | ||
| + | | GHSSignalWord = DANGER | ||
| + | | HPhrases = {{H-phrases|260}} | ||
| + | | ExternalMSDS = | ||
| + | | MainHazards = highly flammable | ||
| + | }} | ||
| + | | Section8 = {{Chembox Related | ||
| + | | Function = [[hydride]] | ||
| + | | OtherFunctn = [[aluminium hydride]]<br/>[[sodium borohydride]]<br/>[[sodium hydride]] | ||
| + | }} | ||
| + | }} | ||
| + | '''Lithium aluminium hydride''', LiAlH<sub>4</sub>, 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]]:<ref>{{citation | last1 = Finholt | first1 = A. E. | last2 = Bond | first2 = A. C. | last3 = Schlesinger | first3 = H. I.| title = Lithium Aluminum Hydride, Aluminum Hydride and Lithium Gallium Hydride, and Some of their Applications in Organic and Inorganic Chemistry | journal = J. Am. Chem. Soc. | year = 1947 | volume = 69 | issue = 5 | pages = 1199–1203 | doi = 10.1021/ja01197a061}}.</ref> | ||
| + | :4 LiH + AlCl<sub>3</sub> → LiAlH<sub>4</sub> + 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:<ref name="HollemanAF">{{Holleman&Wiberg102nd}}.</ref> | ||
| + | :Na + Al + 2 H<sub>2</sub> → NaAlH<sub>4</sub> | ||
| + | |||
| + | LAH is then prepared by [[metathesis reaction]] according to: | ||
| + | :NaAlH<sub>4</sub> + LiCl → LiAlH<sub>4</sub> + NaCl | ||
| + | |||
| + | which proceeds in a high yield of LAH. LiCl is removed by [[filtration]] from an [[ether]]eal solution of LAH, with subsequent precipitation of LAH to yield a product containing around 1% ''w''/''w'' LiCl.<ref name="HollemanAF"/> | ||
==References== | ==References== | ||
| Line 10: | Line 57: | ||
[[Category:Aluminium compounds]] | [[Category:Aluminium compounds]] | ||
[[Category:Hydrides]] | [[Category:Hydrides]] | ||
| − | [[Category:Reagents for organic | + | [[Category:Reagents for organic chemistry]] |
Revision as of 08:13, 20 June 2010
| 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. |
