Lactones


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Related to Lactones: sesquiterpene lactones, Cyclic ester

Lactones

 

internal cyclic esters containing a —COO—group in the ring:

Lactones are classified as β-, γ-, δ-, ε-, and so forth according to the type of hydroxy acid forming the lactone, for example, β-propiolactone (I; boiling point, 155°C), γ-butyrolactone (II; boiling point, 203°-204°C), and δ-valerolactone (III; boiling point, 218°-220°C):

The principal method of lactone synthesis involves the cyclization of hydroxy acids or halogen acids [X—(CH2)nCOOH, where X = OH or a halogen].

Lactones exhibit many properties characteristic of acyclic esters, for example: (1) upon heating with acids or alkalis they hydrolyze to the corresponding hydroxy acids; (2) lactones yield amides upon heating with amines; and (3) lactone polymerization produces linear polyesters [—(CH2)nCOO—]x (the ring is opened at the C—O bond), β-lactones separate into carbon dioxide and olefins upon heating. Higher lactones undergo isomerization to form unsaturated acids at high temperatures.

Lactones are used in organic synthesis, as well as in the preparation of pharmaceuticals and aromatic substances. Some lactones are biologically active substances, for example, β-propiolactone (sterilizing agent).

References in periodicals archive ?
The free acidity lactones and total acidity were determined by a titrimetric method and the following equations:
The study revealed differences in sensitivity of the samples to macrycyclic lactones. Separate experiments revealed genetic variability of heartworms in different geographic locations, which could potentially be associated with varying responses to the drugs.
High doses of kava lactones have been reported to cause hepatotoxic side effects (Whitton 2003).
As addressed in other papers, we are of the opinion that the efficacy of GBE should be solely assigned to its terpene lactones and not to flavonoids.
Irganox HP products are synergistic combinations of phenolic antioxidants, phosphites, and a new Lactone processing stabilizer.
Patch testing with a 6% Compositae mix in petrolatum--arnica (0.5%), German chamomile (2.5%), yarrow (1%), tansy (1%), and feverfew (1%)--is now favored in the literature over testing with a 0.1% sesquiterpene lactone mix in petrolatum (alantolactone, costunolide, and dehydrocostus lactone).
These tin-zeolite catalysts produced the desired esters and lactones from the Baeyer-Villiger oxidation when the researchers substituted hydrogen peroxide for the typical acid ingredient.
The kava product should be standardized to 70 mg of kava lactones per capsule, and the daily dose should be in the range of 140-280 mg kava lactones.
This book describes the activation of carbon dioxide by metal complexes thus yielding synthetic pathways to carboxylic acids, esters, lactones, etc.
Both natural and synthetic lactones are a well-known group of compounds due to their interesting and useful properties.
Important wood chemicals, which could be supposed to be impact molecules, include naturally present cis and trans methyl-octalactone (whisky lactones, with a coconut flavor in pure state), trans-2-nonenal (sawdust smell), toasting releasing volatile phenols: guaiacol, 4-methyl-guaiacol and eugenol (spicy and smoky smells) and vanillin (vanilla smell).
They also contain sesquiterpene lactones which are 15-carbon compounds consisting of three isoprene units and a lactone group.