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Carboxylic acid esters / Lactones


Esters are derivatives of carboxylic acids and lactones are cyclic carboxylic esters. They both can be prepared by esterification from corresponding acids and alcohols but in case of lactones this process is intramolecular. The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of acid catalyst. Since esterification is highly reversible, the yield of the ester can be improved using Le Chatelier's principle (alcohol in large excess, dehydrating agent, removal of water with the use of Dean-Stark apparatus). Another popular methods of preparation are alcoholysis of acyl chlorides and acid anhydrides, transesterification and the Baeyer–Villiger oxidation that forms an ester from a ketone or a lactone from a cyclic ketone. Esters are versatile intermediates in synthesis, they can undergo hydrolysis, saponification and reduction to aldehydes or alcohols. Esters also serve as a protecting group for carboxylic acids.