reduced to the alcohol. The reaction occurs by nucleophilic addition of hydride to the carbonyl
group. The reaction mechanism is shown in Figure 8.16.
Figure 8.16. Reduction of a Carboxylic Acid to a Primary Alcohol
Reaction occurs by nucleophilic addition of hydride and proceeds through an aldehyde intermediate.
Lithium aluminum hydride is a strong reducing agent that can successfully reduce a carboxylic acid;
a gentler reducing agent like sodium borohydride (NaBH 4 ) is not strong enough to reduce carboxylic
acids.
KEY CONCEPT
Carboxylic acids can be reduced by LiAlH 4 , but not the less reactive NaBH 4.DECARBOXYLATION
Decarboxylation describes the complete loss of the carboxyl group as carbon dioxide. This is a
common way of getting rid of a carbon from the parent chain. 1,3-dicarboxylic acids and other β-
keto acids may spontaneously decarboxylate when heated. Under these conditions, the carboxyl
group is lost and replaced with hydrogen. Because both the electrophile and nucleophile are in the
same molecule, the reaction proceeds through a six-membered ring in its transition state, as shown