LiAlH₄ Reduction of Esters
LiAlH₄ Reduction of Esters: LiAlH₄ (LAH) is a powerful reducing agent that reduces an ester all the way to alcohols.
What happens
LiAlH₄ (LAH) is a powerful reducing agent that reduces an ester all the way to alcohols. The main carbonyl product is a primary alcohol (COOR → CH₂OH) and the carbonyl carbon is retained.
Reaction summary
Ester + LiAlH₄, then workup → alcohols (COOR → CH₂OH)
Reagents and conditions
- Starting material: Ethyl benzoate (ester)
- Reagents: LiAlH₄ (LAH)
- Conditions: 1. LiAlH₄ (LAH); 2. H₂O / H₃O⁺ workup
- Products: Benzyl alcohol (primary alcohol); Ethanol (alcohol from the –OR group)
Common mistakes
- The workup comes after LiAlH₄. LiAlH₄ reacts violently with water, so you don't mix them together at the start.
Memory trick
LAH doesn’t know when to stop. DIBAL-H: ester → aldehyde (STOP). LiAlH₄: ester → aldehyde → alcohol.