Lactide


Lactide is the lactone cyclic di-ester derived from lactic acid. With the formula 2, it exists in three different stereoisomeric forms. All are colorless or white solids. Lactide has attracted great interest because it is derived from abundant renewable resources and is the precursor to a polymer similar to polystyrene, but biodegradable.

Stereoisomers

Lactic acid is chiral such that -lactic acid and -lactic acid exist. Furthermore, these enantiomers do not racemize readily. Thus, formation of lactide from two equivalents of lactic acid gives rise to three stereoisomers:
All three stereosiomers undergo epimerisation in the presence of organic and inorganic bases in solution.

Polymerization

Lactide can be polymerized to polylactic acid. Depending on the catalyst, syndiotactic or a heterotactic polymers can result. The resulting materials, polylactic acid, have many attractive properties.