Lactide

Lactide is the lactone cyclic di-ester derived from lactic acid (2-hydroxypropionic acid). With the formula (OCHCO2)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.[3]

Lactide
Lactide.png
Names
Other names
Dilactid, (R,R)-3,6-Dimethyl-1,4-dioxan-2,5-dion, (S,S)-3,6-Dimethyl-1,4-dioxan-2,5-dion, (meso)-3,6-Dimethyl-1,4-dioxan-2,5-dion, (R,R)-2,5-Dimethyl-3,6-dioxo-1,4-dioxan, (S,S)-2,5-Dimethyl-3,6-dioxo-1,4-dioxan, (meso)-2,5-Dimethyl-3,6-dioxo-1,4-dioxan
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.002.245 Edit this at Wikidata
EC Number
  • 202-468-3
UNII
Properties
C6H8O4
Molar mass 144.126 g·mol−1
Melting point 95 to 97 °C (203 to 207 °F; 368 to 370 K) [(S,S)-Lactide and (R,R)-Lactide][2]
Hydrolyses to lactic acid[2]
Solubility soluble in chloroform, methanol
slightly soluble in benzene

[2]

Hazards
GHS pictograms GHS07: Harmful
GHS Signal word Warning
H319
P264, P280, P305+351+338, P337+313
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

StereoisomersEdit

Lactic acid is chiral such that (R)-lactic acid and (S)-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:

(R,R)-Lactide (left above), (S,S)-lactide (right above) and meso-lactide (below)
Ball-and-stick models of the above isomers

All three stereosiomers undergo epimerisation in the presence of organic and inorganic bases in solution.[4]

PolymerizationEdit

Lactide can be polymerized to polylactic acid (polylactide). Depending on the catalyst, syndiotactic or a heterotactic polymers can result. The resulting materials, polylactic acid, have many attractive properties.[5][6]

 

ReferencesEdit

  1. ^ Sigma Aldrich product page for lactide Retrieved 8th of July 2015
  2. ^ a b c Römpp Online Chemielexikon Version 3.3 aufgerufen am 25. März 2009
  3. ^ Andreas Künkel, Johannes Becker, Lars Börger, Jens Hamprecht, Sebastian Koltzenburg, Robert Loos, Michael Bernhard Schick, Katharina Schlegel, Carsten Sinkel, Gabriel Skupin and Motonori Yamamoto (2016). "Polymers, Biodegradable". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–29. doi:10.1002/14356007.n21_n01.pub2. ISBN 9783527306732.CS1 maint: uses authors parameter (link)
  4. ^ Shuklov, Ivan A.; Jiao, Haijun; Schulze, Joachim; Tietz, Wolfgang; Kühlein, Klaus; Börner, Armin (2011-03-02). "Studies on the epimerization of diastereomeric lactides". Tetrahedron Letters. 52 (9): 1027–1030. doi:10.1016/j.tetlet.2010.12.094. ISSN 0040-4039.
  5. ^ R. Auras; L.-T. Lim; S. E. M. Selke; H. Tsuji (2010). Poly(lactic acid): Synthesis, Structures, Properties, Processing, and Applications. Wiley. ISBN 978-0-470-29366-9.
  6. ^ Odile Dechy-Cabaret, Blanca Martin-Vaca and Didier Bourissou (2004). "Controlled Ring-Opening Polymerization of Lactide and Glycolide". Chem. Rev. 104 (12): 6147–76. doi:10.1021/cr040002s. PMID 15584698.CS1 maint: uses authors parameter (link)