Illustrated Glossary of Organic Chemistry

Carboxylate ester: A molecule or functional group bearing a carbonyl group bonded to an OR group. These molecules are called carboxylate esters because they are usually derived from an esterification reaction involving a carboxylic acid and an alcohol, but carboxylate esters can be produced by other reactions as well. The term 'ester' often refers to a carboxylate ester, but it can also refer to an ester of another acid, such as a phosphate ester.

Shown here is the Fischer esterification reaction, a traditional method for carboxylate ester synthesis. In this example, benzoic acid (a carboxylic acid) is reacted with methanol (an alcohol and the reaction solvent) in the presence of a catalytic amount of a strong acid (such as sulfuric acid).


Another common method to produce a carboxylate ester where the OR group is not tertiary is by an S_N2 alkylation reaction. For example, benzoic acid (a carboxylic acid) is converted into benzoate ion (a carboxylate ion and reaction intermediate) with potassium carbonate (a mild base) in DMF (the solvent). This carboxylate ion is then alkylated with ethyl iodide (a primary alkyl halide) via the S_N2 reaction mechanism.