Lactones

Lactones, the cyclic esters of hydroxy acids, resulting from the internal elimination of water between the hydroxyl and carboxyl groups, this reaction taking place when the hydroxy acid is liberated from its salts by a mineral acid. The α and β-hydroxy acids do not form lactones, the tendency for lactone formation appearing first with the γ-hydroxy acids, thus γ-hydroxybutyric acid, CH2OH·CH2·CH2·CO2H, yields γ-butyrolactone,  These compounds may also be prepared by the distillation of the γ-halogen fatty acids, or by the action of alkaline carbonates on these acids, or from βγ\- or γδ-unsaturated acids by digestion with hydrobromic acid or dilute sulphuric acid. The lactones are mostly liquids which are readily soluble in alcohol, ether and water. On boiling with water, they are partially reconverted into the hydroxy acids. They are easily saponified by the caustic alkalis.

On the behaviour of lactones with ammonia, see H. Meyer, Monatshefte, 1899, 20, p. 717; and with phenylhydrazine and hydrazine hydrate, see R. Meyer, Ber., 1893, 26, p. 1273; L. Gattermann, Ber., 1899, 32, p. 1133, E. Fischer, Ber., 1889, 22, p. 1889.

γ-Butyrolactone is a liquid which boils at 206° C. It is miscible with water in all proportions and is volatile in steam, γ-valerolactone, , is a liquid which boils at 207-208° C. δ-lactones are also known, and may be prepared by distilling the δ-chlor acids.