Acid Halides to Alcohols: LiAlH₄ Reduction

Acid halides are reduced to alcohols in the presence of a strong reducing agent like lithium aluminum hydride.

The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as the final product.

However, it is possible to stop the reaction at the aldehyde by using a milder reducing agent like diisobutylaluminum hydride or lithium tri(t-butoxy)aluminum hydride.