Lactonen

Lactones, also referred to as lactonen in some languages, are a class of cyclic esters formed by intramolecular condensation of hydroxy acids. They occur over a range of ring sizes, typically from three to seven atoms, and are categorized as beta-, gamma-, delta-, or epsilon-lactones according to the size of their ring. The ring size governs reactivity, stability, and physical properties.

Chemically, a lactone arises when the hydroxy group of a hydroxy acid reacts with its carboxyl group, eliminating water in an intramolecular esterification. Naming uses the original hydroxy acid; for example beta-propiolactone (3-member ring), gamma-butyrolactone (GBL), delta-valerolactone, and epsilon-caprolactone. Gamma- and delta-lactones are among the most common in nature and industry, contributing to flavors, fragrances, and solvents.

Occurrence and production: Lactones occur in nature as aroma and flavor compounds in fruits, dairy products, and other foods; several have characteristic fruity notes (for example gamma- and delta-lactones such as peach and coconut flavors). Industrially, lactones are prepared by intramolecular esterification of hydroxy acids under acid or base catalysis, or by ring-opening polymerization of lactone monomers to produce polyesters such as polycaprolactone, a biodegradable polymer used in packaging and biomedicine.

Uses and reactions: Lactones participate in hydrolysis to regenerate the corresponding hydroxy acids, or in nucleophilic ring-opening reactions. They serve as solvents (for instance gamma-butyrolactone), and as monomers for biodegradable polymers; some lactones have fragrance and flavor applications.

Safety: Hazard profiles vary with ring size and substitution. Beta-propiolactone is a carcinogen and requires careful handling; many lactones are irritants or have low toxicity. Proper laboratory practices and regulatory guidance apply.