Carboxylato

Carboxylato refers to the carboxylate anion, R–COO−, formed when a carboxylic acid loses a proton. The term is used in organic, inorganic, and coordination chemistry to describe ligands derived from carboxylic acids, as well as salts containing the carboxylate group.

Structure and properties: The carboxylate anion is stabilized by resonance between the two oxygen atoms; the negative charge is delocalized over the O–C–O framework, giving a planar, typically trigonal geometry at the carboxyl carbon. This delocalization explains the stability of carboxylate salts and the tendency of carboxylates to engage in diverse binding modes to metal centers.

Coordination chemistry: Carboxylates act as ligands that can bind metals in various modes. Monodentate binding uses one oxygen, bidentate chelation uses both oxygens, and bridging modes link two or more metal centers. In polydentate carboxylates such as oxalate and citrate, multiple coordination sites enable complex structures and functional properties in catalysis and materials science.

Preparation and examples: Carboxylate salts form by neutralizing carboxylic acids with bases (for example, acetic acid with NaOH gives sodium acetate). Common carboxylates include acetate, benzoate, oxalate, and citrate. They are also produced in metathesis reactions and in various biological processes.

Applications and occurrence: Carboxylates play roles in buffering systems (e.g., acetate buffer), catalysis, and materials chemistry. In biology, many biomolecules contain carboxylate groups that are deprotonated at physiological pH, such as the side chains of aspartate and glutamate and the carboxylate groups of fatty acids and amino acids.