Product Code Database
Lactones are cyclic . They are derived from the corresponding hydroxycarboxylic acids by esterification. They can be saturated or unsaturated.
Lactones are formed by lactonization, the intramolecular esterification of the corresponding hydroxycarboxylic acids.
| 3 | α-lactone | Oxiran-2-one | Acetolactone | |
| 4 | β-lactone | Oxetan-2-one | ||
| 5 | γ-lactone | Oxolan-2-one | γ-Butyrolactone | |
| 6 | δ-lactone | Oxan-2-one | ||
| 7 | ε-lactone | Oxepan-2-one |
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. The first carbon atom after the carbon in the -COOH group on the parent compound is labelled α, the second will be labeled β, and so forth. Therefore, the prefixes also indicate the size of the lactone ring: α-lactone = 3-membered ring, β-lactone = 4-membered, γ-lactone = 5-membered, δ-lactone = 6-membered, etc. Macrocyclic lactones are known as macrolactones.
The other suffix used to denote a lactone is -olide, used in substance class names like butenolide, macrolide, cardenolide or bufadienolide.
To obtain the preferred IUPAC names, lactones are named as heterocyclic pseudoketones by adding the suffix 'one', 'dione', 'thione', etc. and the appropriate multiplicative prefixes to the name of the heterocyclic parent hydride. (2025). 9780854041824, The Royal Society of Chemistry. ISBN 9780854041824
In 1880 the German chemist Wilhelm Rudolph Fittig extended the name "lactone" to all intramolecular carboxylic esters. From p. 62: "Es ist wünschenswerth, für diese Gruppe von Verbindungen, deren bis jetzt einfachster Repräsentant der im Vorstehenden beschriebene Körper ist, eine allgemeine Bezeichnungsweise zu haben, und da der Name "Lactide" nicht anwendbar ist, weil dann das Lactid κατ εξοχην kein Lactid sein wurde, so schlagen wir als Gruppenbezeichnung den Namen "Lactone" vor". (It's desirable for this group of compounds — whose simplest representative until now has been the substance that's described in the preceding — to have a general designation, and since the name "lactide" isn't applicable because then the archetypal lactide would not be a lactide, we therefore suggest the name "lactone" as the designation of this group of.)
5-Membered γ-lactones and 6-membered δ-lactones are prevalent. β-lactones appear in a number of natural products. αLactones can be detected as transient species in mass spectrometry experiments.Detlef Schröder, Norman Goldberg, Waltraud Zummack, Helmut Schwarz, John C. Poutsma and Robert R. Squires (1997), Generation of α-acetolactone and the acetoxyl diradical •CH2COO• in the gas phase. International Journal of Mass Spectrometry and Ion Processes, Volumes 165-166, November issue, Pages 71-82.
Macrocyclic lactones are also important natural products. Lactones are present in oak wood, and they contribute to the flavour profile of .
In one industrial synthesis of oxandrolone the key lactone-forming step is an organic reaction – esterification. Development of a Commercial Process to Produce Oxandrolone John E. Cabaj, David Kairys, and Thomas R. Benson Org. Process Res. Dev.; 2007; 11(3) pp 378–388; (Article) The complete reaction sequence is bromination to a haloketone (not displayed), elimination reaction with lithium chloride to an enone, organic oxidation by osmium tetroxide and lead tetraacetate with ring-opening and finally reduction of the aldehyde to the alcohol with sodium borohydride and intramolecular lactone formation
In halolactonization, an alkene is attacked by a halogen via electrophilic addition with the cationic intermediate captured intramolecularly by an adjacent carboxylic acid.Organic Syntheses, Coll. Vol. 7, p.164 (1990); Vol. 64, p.175 ( 1986) Article link
Specific methods include Yamaguchi esterification, Shiina macrolactonization, Corey-Nicolaou macrolactonization, Baeyer–Villiger oxidation and nucleophilic abstraction.
An alternative radical reaction yielding γ-lactones is the manganese-mediated coupling.
Lactones also react with amines to give the ring-opened alcohol and amide.
Macrocyclic lactones (cyclopentadecanolide, 15-pentadec-11/12-enolide) have odors similar to macrocyclic ketones of animal origin (muscone, civetone).
|
|
