Lactide
Encyclopedia
Lactide is the cyclic di-ester
of lactic acid
, i.e., 2-hydroxypropionic acid. Lactic acid
cannot form a lactone
as other hydroxy acids do because the hydroxy group is too close to the carboxylic group. Instead, lactic acid
first forms a dimer, which is similar to a 5-hydroxyacid. The dimer contains a hydroxy group at a convenient distance from the carboxylic group for the formation of a lactone. Indeed, the dimer readily forms a six-membered cyclic diester known as lactide. Lactides may be prepared by heating lactic acid in the presence of an acid catalyst.
In general, a lactide is the cyclic diester, i.e., the di-lactone
of two molecules of any 2-hydroxycarboxylic acid.
; two enantiomeric forms, (R)-lactic acid and (S)-lactic acid, may exist. Thus, lactide formed from two equivalents of lactic acid consists of two stereocenters. Three different stereoisomers of lactide are known:
to polylactic acid
(polylactide) using suitable catalysts, with either syndiotactic or a heterotactic stereocontrol, to give materials with many useful properties.:
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
of lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
, i.e., 2-hydroxypropionic acid. Lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
cannot form a lactone
Lactone
In chemistry, a lactone is a cyclic ester which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule...
as other hydroxy acids do because the hydroxy group is too close to the carboxylic group. Instead, lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
first forms a dimer, which is similar to a 5-hydroxyacid. The dimer contains a hydroxy group at a convenient distance from the carboxylic group for the formation of a lactone. Indeed, the dimer readily forms a six-membered cyclic diester known as lactide. Lactides may be prepared by heating lactic acid in the presence of an acid catalyst.
In general, a lactide is the cyclic diester, i.e., the di-lactone
Lactone
In chemistry, a lactone is a cyclic ester which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule...
of two molecules of any 2-hydroxycarboxylic acid.
Stereoisomers
Lactic acid is chiralChirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
; two enantiomeric forms, (R)-lactic acid and (S)-lactic acid, may exist. Thus, lactide formed from two equivalents of lactic acid consists of two stereocenters. Three different stereoisomers of lactide are known:
Polymerization
Lactide can be polymerizedPolymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
to polylactic acid
Polylactic acid
Poly or polylactide is a thermoplastic aliphatic polyester derived from renewable resources, such as corn starch , tapioca products or sugarcanes...
(polylactide) using suitable catalysts, with either syndiotactic or a heterotactic stereocontrol, to give materials with many useful properties.: