Weekend Reading: Reagent - Lithium Aluminium Hydride

Reagent Name: Lithium Aluminium Hydride

Molecular Formula: LiAlH₄

Main Role in Organic Reactions: LiAlH₄ acts as a reducing agent in most of the organic reactions

Reaction Examples:

1. Reduction of carbonyl compounds to alcohols

2. Conversion of Alkyl Halides to Alkanes

3. Conversion of Alkyl Cyanides to Primary Amines

 Mechanism of Action:

 LiAlH₄ is a source of hydride (H^-) ions. Hydride ions produced by the reagent act as nulceophiles and attack the electrophillic centre in the reactant bringing about either nucleophilic addition or nucleophilic substitution depending on the nature of the reagent. In case of nucleophilic addition the salt formed is given acid treatment to release the alcohol.

Mechanism for its reaction bringing about Nucleophilic Addition

Mechanism for its reaction bringing about Nucleophilic Substitution

Related Reagents: NaBH₄ (Sodium Borohydride) is also a reducing agent which is similar in action but less reactive than LiAlH_­4.

Question: Can you explain why NaBH₄ is less reactive than LiAlH₄?