Lactide

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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
ECHA InfoCard 100.002.245
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
R-phrases (outdated) R36/37/38
S-phrases (outdated) S26 S37/39
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

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]

Stereoisomers[edit]

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:

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

Polymerization[edit]

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.[4][5]

Polylactide synthesis v.1.png

References[edit]

  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. doi:10.1002/14356007.n21_n01.pub2.CS1 maint: Uses authors parameter (link)
  4. ^ 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.
  5. ^ Odile Dechy-Cabaret, Blanca Martin-Vaca and Didier Bourissou (2004). "Controlled Ring-Opening Polymerization of Lactide and Glycolide". Chem. Rev. 104: 6147–6176. doi:10.1021/cr040002s.CS1 maint: Uses authors parameter (link)