Lactide

Lactide
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
CAS Number	4511-42-6 [(S,S)-Lactide] ; 25038-75-9 [(R,R)-Lactide] ; 13076-19-2 [(R,S)-Lactide = meso-Lactide] ; 26680-10-4 [mixture of three isomers] ; 95-96-5 [mixture of three isomers] ;
3D model (JSmol)	Interactive image;
ChemSpider	7002;
ECHA InfoCard	100.002.245
EC Number	202-468-3;
PubChem CID	7272;
UNII	IJ13TO4NO1 [(S,S)-Lactide] ; 9J7G894K2M [mixture of three isomers] ; 7EH08MWO6M [mixture of three isomers] ;
CompTox Dashboard (EPA)	DTXSID7041253 ;
	InChI InChI=1S/C6H8O4/c1-3-5(7)10-4(2)6(8)9-3/h3-4H,1-2H3 Key: JJTUDXZGHPGLLC-UHFFFAOYSA-N;
	SMILES CC1C(=O)OC(C(=O)O1)C;
Properties
Chemical formula	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]
Solubility in water	Hydrolyses to lactic acid
Solubility	soluble in chloroform, methanol; slightly soluble in benzene
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H319
Precautionary statements	P264, P280, P305+P351+P338, P337+P313
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) 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

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]

Polymerization

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]

References

^ Sigma Aldrich product page for lactide Retrieved 8th of July 2015
^ ^a ^b ^c Römpp Online Chemielexikon Version 3.3 aufgerufen am 25. März 2009
^ "Polymers, Biodegradable". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. 2016. pp. 1–29. doi:10.1002/14356007.n21_n01.pub2. ISBN 9783527306732. {{cite encyclopedia}}: Cite uses deprecated parameter |authors= (help)
^ 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.
^ 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.
^ "Controlled Ring-Opening Polymerization of Lactide and Glycolide". Chem. Rev. 104 (12): 6147–76. 2004. doi:10.1021/cr040002s. PMID 15584698. {{cite journal}}: Cite uses deprecated parameter |authors= (help)

[SigmaAldrich-1] Sigma Aldrich product page for lactide Retrieved 8th of July 2015

[roempp-2] Römpp Online Chemielexikon Version 3.3 aufgerufen am 25. März 2009

[Ullmanns-3] "Polymers, Biodegradable". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. 2016. pp. 1–29. doi:10.1002/14356007.n21_n01.pub2. ISBN 9783527306732. {{cite encyclopedia}}: Cite uses deprecated parameter |authors= (help)

[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] "Controlled Ring-Opening Polymerization of Lactide and Glycolide". Chem. Rev. 104 (12): 6147–76. 2004. doi:10.1021/cr040002s. PMID 15584698. {{cite journal}}: Cite uses deprecated parameter |authors= (help)

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