Lithium aluminium hydride

Lithium Aluminium Hydride

Lithium aluminium hydride (LiAlH4) is a powerful reducing agent commonly used in organic synthesis. It is a white crystalline solid that is highly reactive and has a strong reducing potential. This compound is widely utilized in various chemical reactions due to its ability to donate hydride ions (H-) to organic compounds, resulting in the reduction of functional groups.

Chemical Properties

Lithium aluminium hydride has a molecular weight of 37.95 g/mol and a density of 0.917 g/cm3. It is highly soluble in ethers such as diethyl ether and tetrahydrofuran (THF), but reacts violently with water and alcohols. LiAlH4 is stable under normal conditions but can decompose at high temperatures or in the presence of moisture.

Synthesis

LiAlH4 can be synthesized by the reaction of lithium hydride (LiH) with aluminium chloride (AlCl3) in anhydrous diethyl ether. The reaction proceeds as follows:

2 LiH + AlCl3 → LiAlH4 + 2 LiCl

Applications

Lithium aluminium hydride is primarily used as a reducing agent in organic chemistry. It is commonly employed in the reduction of various functional groups, including carbonyl compounds (aldehydes, ketones, esters, carboxylic acids), epoxides, and nitriles. The hydride ions donated by LiAlH4 react with these functional groups, resulting in the formation of alcohols or amines.

Safety Considerations

LiAlH4 is a highly reactive compound and should be handled with extreme caution. It reacts violently with water, alcohols, and other protic solvents, releasing flammable hydrogen gas. It is also sensitive to air and moisture, which can cause decomposition and potential fire hazards. Proper protective equipment, such as gloves and goggles, should be worn when working with this compound.

References

1. Smith, Michael B., and Jerry March. "Advanced Organic Chemistry: Reactions, Mechanisms, and Structure." Wiley, 2007.

2. Li, Jie Jack. "Name Reactions: A Collection of Detailed Reaction Mechanisms." Springer, 2006.

See Also

• Reducing agent
• Organic synthesis
• Carbonyl compounds
• Functional groups