Carboxilato

Carboxilato, or carboxylate, refers to the carboxylate ion, R-COO−, the conjugate base of a carboxylic acid. It also denotes the salts and esters that contain the carboxylate group, depending on the context. The most common form is the carboxylate anion formed by deprotonation of a carboxyl group.

In aqueous solution, carboxylic acids (R-COOH) dissociate to give R-COO− and H+. The pKa values for simple aliphatic carboxylic acids are typically around 4–5, though substituents can shift this. The carboxylate ion is stabilized by resonance, with negative charge delocalized over the two carbonyl oxygens. This resonance also makes carboxylates good ligands for metals, coordinating through one or both oxygens to form metal carboxylate complexes. In salts, the anion pairs with metal or ammonium cations (for example, sodium acetate, potassium benzoate).

Carboxylate salts have wide practical uses. They form the soaps used in detergents, serve as buffering agents in chemical and biological systems, and act as ligands in coordination and organometallic chemistry. In organic synthesis, carboxylate groups participate in esterification and transesterification chemistry, and carboxylates can function as leaving groups in certain reactions.

Common examples include sodium acetate, potassium benzoate, and calcium palmitate. The carboxylate form is distinct from esters (R-CO-O-R') and anhydrides, which contain non-ionic oxygen substituents rather than a negative charge. Carboxylates are widespread in nature and industry, appearing in metabolism, materials, and applications ranging from detergents to catalysts.