Carboxylic Acids to Primary Alcohols: Hydride Reduction

Carboxylic acids, upon reaction with strong reducing agents such as lithium aluminum hydride followed by hydrolysis, undergo reduction to form primary alcohols.

Weaker reducing agents like lithium tri-tert-butoxyaluminum hydride or diisobutylaluminum hydride cannot reduce carboxylic acids to primary alcohols.

Carboxylic acids can also be reduced to primary alcohols by using borane in the tetrahydrofuran solvent. The main advantage of using borane in reducing a carboxylic acid is that this reagent can selectively reduce carboxylic acid to primary alcohol in the presence of other reducible functional groups, such as a ketone or a nitro group.