Difference between revisions of "Lithium aluminium hydride"

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'''Lithium aluminium hydride''', commonly abbreviated to '''LAH''' is an inorganic compound with the chemical formula LiAlH<sub>4</sub>. It is a strong reducing agent used in organic chemistry.
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{{Chembox
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| Name = Lithium aluminium hydride
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| Reference =
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| IUPACName = Lithium aluminium hydride
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| PIN = Lithium tetrahydridoaluminate(III)
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| SystematicName = Lithium alumanuide
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| OtherNames = LAH<br>Lithal<br>Lithium aluminium hydride<br>Lithium alanate<br>Lithium aluminohydride<br>Lithium tetrahydridoaluminate
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| ImageFile = Lithium aluminium hydride sample bottle by ChemicalForce.jpg
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| ImageSize = 300
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| ImageCaption = LiAlH<sub>4</sub> being poured from its container
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| Section1 = {{Chembox Identifiers
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| 3DMet =
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| Abbreviations =
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| SMILES =
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  }}
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| Section2 = {{Chembox Properties
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| AtmosphericOHRateConstant =
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| Appearance = White or grayish crystals
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| BoilingPt =
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| BoilingPtC =
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| BoilingPt_ref =
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| BoilingPt_notes = Decomposes
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| Density = 0.917 g/cm<sup>3</sup>
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| Formula = LiAlH<sub>4</sub>
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| HenryConstant =
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| LogP =
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| MolarMass =
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| MeltingPt =
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| MeltingPtC = 150
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| MeltingPt_ref =
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| MeltingPt_notes = (decomposes)
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| Odor = Odorless
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| pKa =
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| pKb =
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| Solubility = Reacts
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| SolubleOther = Soluble in [[ether]]s<br>Slightly soluble in [[dibutyl ether]]<br>Insoluble in [[toluene]], [[xylene]]
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| Solubility1 = 11.2332 g/100 ml
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| Solvent1 = diethyl ether
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| Solubility2 = 39.5 g/100 ml
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| Solvent2 = tetrahydrofuran
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| VaporPressure = ~0 mmHg
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  }}
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| Section3 = {{Chembox Structure
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| Coordination =
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| CrystalStruct = Monoclinic
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| Section4 = {{Chembox Thermochemistry
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| DeltaGf = -48.4 kJ/mol
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| DeltaHc =
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| DeltaHf = -117 kJ/mol
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| Entropy = 87.9 J·mol<sup>-1</sup>K<sup>-1</sup>
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| HeatCapacity = 86.4 J·mol<sup>-1</sup>K<sup>-1</sup>
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| Section6 = {{Chembox Hazards
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| AutoignitionPt =
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| ExploLimits =
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| ExternalMSDS = [https://www.fishersci.ca/viewmsds.do?catNo=AC304530250 AcrosOrganics]
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| FlashPt = 125 °C
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| MainHazards = Water-sensitive<br>Pyrophoric
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| OtherCompounds = [[Lithium borohydride]]
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  }}
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}}
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'''Lithium aluminium hydride''', commonly abbreviated to '''LAH''' is an inorganic compound with the chemical formula '''LiAlH<sub>4</sub>'''. It is a strong reducing agent used in organic chemistry.
  
 
==Properties==
 
==Properties==
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==Availability==
 
==Availability==
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LAH is somewhat hard to find, due its sensitivity to air and water. Some people have been able to purchase LAH from Alibaba, from certain chemical sellers.
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LAH is somewhat hard to find, due its sensitivity to air and water. Some people have been able to purchase LAH from Alibaba, from certain chemical sellers. Can also be found on eBay.
  
 
==Preparation==
 
==Preparation==
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LAH can be prepared by reacting [[Lithium hydride|LiH]] with anhydrous [[aluminium chloride]]. The product is purified by dissolving it in ether and then recrystallizing it.
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LAH can be prepared by reacting [[Lithium hydride|LiH]] with anhydrous [[aluminium chloride]], in an aprotic solvent such as [[diethyl ether]]. The product is purified by recrystallizing it from diethyl ether.<ref>[http://pubs.acs.org/doi/abs/10.1021/ja01197a061 J. Am. Chem. Soc., 1947, 69 (5), pp 1199–1203]</ref> THF can also be used as solvent.
  
 
==Projects==
 
==Projects==
 
*Reducing esters to alcohols
 
*Reducing esters to alcohols
 
*Reduce amides to amines
 
*Reduce amides to amines
 +
*Source of hydrogen
  
 
==Handling==
 
==Handling==
 
===Safety===
 
===Safety===
−
LAH will react with water to produce [[lithium hydroxide]] which is corrosive. It will react with both liquid water as well as the moisture from air.
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LAH will react with water to produce [[lithium hydroxide]] which is corrosive. It will react with both liquid water as well as the moisture from air. Wear proper protection, like gloves, when handling this compound.
  
 
===Storage===
 
===Storage===
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It's best stored in a dry airtight container or bags, under inert or reducing conditions if possible. LAH is also a fire hazard, and in its powdered form it's pyrophoric.
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LAH is best stored in a dry airtight container or bags, under inert or reducing conditions if possible. LAH is also a fire hazard, and in its powdered form can be pyrophoric.
  
 
===Disposal===
 
===Disposal===
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*[http://www.sciencemadness.org/talk/viewthread.php?tid=18679 heating lithium aluminum hydride with heating mantle]
 
*[http://www.sciencemadness.org/talk/viewthread.php?tid=18679 heating lithium aluminum hydride with heating mantle]
 
*[http://www.sciencemadness.org/talk/viewthread.php?tid=10207 Lithium Al Hydride quick question]
 
*[http://www.sciencemadness.org/talk/viewthread.php?tid=10207 Lithium Al Hydride quick question]
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*[http://www.sciencemadness.org/talk/viewthread.php?tid=72539 LAH storage]
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*[http://www.sciencemadness.org/talk/viewthread.php?tid=84228 Storage of LiAlH4]
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[[Category:Chemical compounds]]
 
[[Category:Chemical compounds]]
 
[[Category:Inorganic compounds]]
 
[[Category:Inorganic compounds]]
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[[Category:Lithium compounds]]
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[[Category:Aluminium compounds]]
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[[Category:Hydrogen compounds]]
 
[[Category:Metal hydrides]]
 
[[Category:Metal hydrides]]
 
[[Category:Reducing agents]]
 
[[Category:Reducing agents]]
 
[[Category:Materials unstable in acidic solution]]
 
[[Category:Materials unstable in acidic solution]]
 
[[Category:Materials that react with water]]
 
[[Category:Materials that react with water]]
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[[Category:Lithium compounds]]
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[[Category:Air-sensitive materials]]
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[[Category:Hydrogen compounds]]
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[[Category:Aluminium compounds]]
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[[Category:Pyrophoric materials]]
 
[[Category:Pyrophoric materials]]
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[[Category:Desiccants]]
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[[Category:DEA SS List]]

Latest revision as of 17:39, 29 February 2020

Stub.png This article is a stub. Please help Sciencemadness Wiki by expanding it, adding pictures, and improving existing text.
Lithium aluminium hydride
Lithium aluminium hydride sample bottle by ChemicalForce.jpg
LiAlH4 being poured from its container
Names
IUPAC name
Lithium aluminium hydride
Preferred IUPAC name
Lithium tetrahydridoaluminate(III)
Systematic IUPAC name
Lithium alumanuide
Other names
LAH
Lithal
Lithium aluminium hydride
Lithium alanate
Lithium aluminohydride
Lithium tetrahydridoaluminate
Properties
LiAlH4
Appearance White or grayish crystals
Odor Odorless
Density 0.917 g/cm3
Melting point 150 °C (302 °F; 423 K) (decomposes)
Boiling point Decomposes
Reacts
Solubility Soluble in ethers
Slightly soluble in dibutyl ether
Insoluble in toluene, xylene
Solubility in diethyl ether 11.2332 g/100 ml
Solubility in tetrahydrofuran 39.5 g/100 ml
Vapor pressure ~0 mmHg
Thermochemistry
87.9 J·mol-1K-1
-117 kJ/mol
Hazards
Safety data sheet AcrosOrganics
Flash point 125 °C
Related compounds
Related compounds
 Lithium borohydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Lithium aluminium hydride, commonly abbreviated to LAH is an inorganic compound with the chemical formula LiAlH4. It is a strong reducing agent used in organic chemistry.

Properties

Chemical

LAH is sensitive to water, and reacts vigorously to release hydrogen.

LiAlH4 + H2O → LiOH + Al(OH)3 + 4 H2

LAH is metastable at room temperature. During prolonged storage it slowly decomposes to Li3AlH6 and LiH.

LAH is a strong reducing agent, it will convert esters, carboxylic acids, acyl chlorides, aldehydes, and ketones into the corresponding alcohols. Similarly, it converts amide, azide, imine, nitrile, nitro and oxime compounds into amines. LAH is most commonly used for the reduction of esters and carboxylic acids to primary alcohols.

Physical

LAH is a white solid, however commercial samples are usually gray due to impurities. It can be purified by recrystallization from diethyl ether. The pure powdered material is pyrophoric, but its large crystals are not. LAH will react with water to release hydrogen, so samples are usually stored is airtight bags, away from any moisture. LAH is soluble in many ethereal solutions, but is more stable in THF than diethyl ether, even though it's less soluble in the former than the latter.

Availability

LAH is somewhat hard to find, due its sensitivity to air and water. Some people have been able to purchase LAH from Alibaba, from certain chemical sellers. Can also be found on eBay.

Preparation

LAH can be prepared by reacting LiH with anhydrous aluminium chloride, in an aprotic solvent such as diethyl ether. The product is purified by recrystallizing it from diethyl ether.[1] THF can also be used as solvent.

Projects

  • Reducing esters to alcohols
  • Reduce amides to amines
  • Source of hydrogen

Handling

Safety

LAH will react with water to produce lithium hydroxide which is corrosive. It will react with both liquid water as well as the moisture from air. Wear proper protection, like gloves, when handling this compound.

Storage

LAH is best stored in a dry airtight container or bags, under inert or reducing conditions if possible. LAH is also a fire hazard, and in its powdered form can be pyrophoric.

Disposal

The byproducts or neutralizing LAH are lithium and aluminium compounds, usually lithium hydroxide or carbonate and aluminium oxide. They can either be recycled (lithium especially) or disposed in centers that accept aluminium wastes.

See also

References

  1. ↑ J. Am. Chem. Soc., 1947, 69 (5), pp 1199–1203

Relevant Sciencemadness threads

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