Tricarboxylic

Tricarboxylic is a chemical descriptor used for molecules that contain three carboxyl groups (-CO2H). When all three groups are present as carboxyls, the compound is typically tribasic, able to donate up to three protons in aqueous solution, with multiple dissociation steps corresponding to successive pKa values.

Citric acid is the best-known example of a tricarboxylic acid. It is a hydroxytricarboxylic acid with three carboxyl groups and one hydroxyl group. Its three dissociable protons have approximate pKa values around 3.1, 4.8, and 6.4, reflecting its triprotic acidity. Citric acid is a key metabolite in the citric acid cycle and is widely used as a food additive, buffering agent, and chelating agent.

Other tricarboxylic acids include aromatic examples such as trimesic acid (benzene-1,3,5-tricarboxylic acid) and trimellitic acid (benzene-1,2,4-tricarboxylic acid). There are numerous aliphatic and cyclic structures, all characterized by three carboxyl groups. These compounds form salts (tricarboxylates) and esters, and their multiple carboxylate sites give them distinctive coordination behavior with metal ions, which is exploited in chemistry and materials science.

Biological and industrial relevance varies by structure. In biology, tricarboxylic acids such as citric acid connect to central metabolism; in industry, they serve as acidity regulators, chelating agents, monomers for polymers and porous materials, or precursors in synthesis. The term “tricarboxylic” thus encompasses a broad class of molecules defined by the presence of three carboxyl functional groups.