Lactone

Lactones are usually named according to the precursor acid molecule (aceto = 2 carbon atoms, propio = 3, butyro = 4, valero = 5, capro = 6, etc.

), with a -lactone suffix and a Greek letter prefix that specifies the number of carbon atoms in the heterocycle — that is, the distance between the relevant -OH and the -COOH groups along said backbone.

[3]The other suffix used to denote a lactone is -olide, used in substance class names like butenolide, macrolide, cardenolide or bufadienolide.

Lactic acid, in turn, derives its name from its original isolation from soured milk (Latin: lac, lactis).

The name was coined in 1844 by the French chemist Théophile-Jules Pelouze, who first obtained it as a derivative of lactic acid.

[5] An internal dehydration reaction within the same molecule of lactic acid would have produced alpha-propiolactone, a lactone with a 3-membered ring.

In 1880 the German chemist Wilhelm Rudolph Fittig extended the name "lactone" to all intramolecular carboxylic esters.

[6] Lactone rings occur widely as building blocks in nature, such as in ascorbic acid, kavain, nepetalactone, gluconolactone, hormones (spironolactone, mevalonolactone), enzymes (lactonase), neurotransmitters (butyrolactone, avermectins), antibiotics (macrolides like erythromycin; amphotericin B), anticancer drugs (vernolepin, epothilones), phytoestrogens (resorcylic acid lactones, cardiac glycosides).

[11][12] In halolactonization, an alkene is attacked by a halogen via electrophilic addition with the cationic intermediate captured intramolecularly by an adjacent carboxylic acid.