5337. l-Lactic Acid

Nomenclature

CAS number: 79-33-4
(2S)-2-Hydroxypropanoic acid; l(+)-lactic acid; (S)-(+)-lactic acid; dextrorotatory lactic acid; d-lactic acid; sarcolactic acid; paralactic acid; Fleishmilchsure; l-Milchsure.
C3H6O3; mol wt 90.08.
C 40.00%, H 6.71%, O 53.28%.

Description and references

Occurs in small quantities in the blood and muscle fluid of man and animals. The lactic acid concn increases in muscle and blood after vigorous activity. l(+)-Lactic acid is also present in liver, kidney, thymus gland, human amniotic fluid, and other organs and body fluids. Obtained by resolution of dl-lactic acid: Purdie, Walker, J. Chem. Soc. 61, 754 (1892); Borsook et al., J. Biol. Chem. 102, 449 (1933). Convenient laboratory prepn from glucose by fermentation by Lactobacillus delbrueckii: Brin, Biochem. Prep. 3, 61 (1953). Prepn from hexoses using B. dextrolacticus: Andersen, Greaves, Ind. Eng. Chem. 34, 1522 (1942). Monograph: M. Brin, R. H. Dunlop, “Chemistry and Metabolism of l- and d-Lactic Acids” in Ann. N.Y. Acad. Sci. 119, 851-1165 (1965).

Chemical structure

Properties

Crystals from acetic acid or chloroform, mp 53°. [α]546.121-22 +2.6° (c = 2.5). pK at 25°, 3.79. Forms salts with many metals. The salts are more sol in water than the salts of the racemic acid. Most of the salts are levoratory.

Derivative

Zinc l()-lactate dihydrate.
Zn(C3H5O3)2.2H2O; mol wt 279.58.
Zn 23.40%, C 25.78%, H 5.05%, O 45.78%.

Properties

Prisms. [α]D25 8.2° (c = 2.5 in water).