lactonas

Lactones are cyclic esters formed by intramolecular esterification of hydroxy acids. When a molecule contains both a hydroxyl and a carboxyl group, cyclization can occur with loss of water to yield a ring-structured ester. Ring size varies; five- and six-membered rings (gamma- and delta-lactones) are the most common because they balance strain and stability, though larger and smaller rings exist.

Formation can proceed by heating, dehydration under acid or base catalysis, or activation of the carboxyl group to promote cyclization. Natural sources include metabolic pathways and lipid oxidation, with many lactones appearing in essential oils, dairy flavors, and fruit notes. Common examples in flavors and fragrances are gamma- and delta-lactones, which impart coconut, peach, and creamy notes.

In industry, lactones are used or generated in several ways. They serve as monomers in ring-opening polymerization to produce polyesters such as polycaprolactone. Similarly, lactic acid can form lactide, a dimer used to manufacture polylactic acid (PLA). The ester linkage in lactones also makes them susceptible to hydrolysis, enabling controlled degradation under acidic or basic conditions, which is relevant to processing and environmental fate.

For researchers, lactones are characterized by the interplay of ring strain, carbonyl reactivity, and substituent effects, which influence their kinetics and odors. The term lactona is used in several languages; in English the common term is lactone.