Chemical Reactions

Carboxylic acids owe their rich chemistry to three separate reactive sites in the $-COOH$ group: the acidic $O-H$ bond, the $C-OH$ bond (which behaves somewhat like the C–OH of an alcohol), and the carboxyl carbon itself, which can be lost entirely as $CO_2$. In addition, once a carboxyl group is attached to a hydrocarbon chain or ring, it changes how that hydrocarbon part reacts. The reactions of carboxylic acids are therefore grouped into four broad categories:

1. Reactions involving cleavage of the O–H bond — acidic behaviour: reaction with metals, alkalis, and weak bases such as carbonates/hydrogencarbonates.
2. Reactions involving cleavage of the C–OH bond — the $-OH$ is replaced or converted, giving anhydrides, esters, acid chlorides, and amides.
3. Reactions involving the whole $-COOH$ group — reduction of the group to $-CH_2OH$, and decarboxylation, where the entire carboxyl carbon leaves as $CO_2$. …