Lactone

Lactones is known in organic chemistry, heterocyclic compounds containing directly on the same carbon atom of a carbonyl group within the molecule, an ester linkage, i.e., an oxygen bridge. It is intramolecular esters of hydroxycarboxylic acids.

Nomenclature

By Greek letters, the position or the position ( existing at the corresponding hydroxycarboxylic acid ) hydroxyl group is given in relation to the carboxy group, the carboxy group of the adjacent carbon atom is referred to as α -configuration, β -position when the next and so on.

Lactones are named by adding the ending -olide the name of the corresponding hydrocarbon, wherein the position of participating in the ring-closing carbon atom is expressed as a number, such as propane -3 -olide = β -propiolactone.

Occurrence

Lactones are widely used as ingredients in various types of fatty food and fruit from the aroma - providing component. δ -decalactone is an important flavoring in milk fat and butter and thus induces a sweet note.

γ -decalactone is a flavoring in pineapple, apricot, strawberry, passion fruit, mango and peach. In apricot nectarine and peach one finds a variety of γ - lactones with six to twelve carbon atoms, and δ - lactones with eight to twelve carbon atoms, which smell like coconut either, furchtig - peach -like or fruity- greasy.

Production

While α - lactones, the simplest representative is the Acetolacton, known only as unstable intermediates and the β - lactones ( four rings ) are displayed only under special conditions, the γ - and δ - lactones ( five- or six-membered rings ) are easy to prepare and stable heterocyclic compounds. γ -Lactones can be obtained by evaporation of dilute aqueous solutions of the corresponding γ - hydroxycarboxylic acids. If the carboxyl group and the hydroxyl group further apart, the lactones are rapidly unstable. Among the best known ε - lactones heard ε -caprolactone, a lactone of caproic acid. From ε -caprolactone polyester to be produced. Copolymerization of ε -caprolactone with lactic acid leads to polyester, which are biodegradable.

Example of a lactone; the formation of γ -butyrolactone from γ -hydroxybutyric acid:

Another method to produce lactones, the Baeyer-Villiger oxidation. This cyclic ketones with peroxy carboxylic acids with ring expansion are oxidized to lactones. The Baeyer -Villiger oxidation cyclohexanone provides the ε -caprolactone industrially produced in substantial quantities, a starting material for the preparation of polyesters and polyethers.

Examples

• Macrolides