Names | |
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Preferred IUPAC name
4-Hydroxy-6-methyl-2H-pyran-2-one | |
Other names
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Identifiers | |
3D model (
JSmol)
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ChEBI | |
ChemSpider | |
ECHA InfoCard | 100.010.564 |
EC Number |
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PubChem
CID
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UNII | |
CompTox Dashboard (
EPA)
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Properties | |
C6H6O3 | |
Molar mass | 126.12 g mol−1 |
Appearance | light yellow crystal powder |
Density | 1.348 g cm−3 |
Melting point | 188 to 190 °C (370 to 374 °F; 461 to 463 K) |
Boiling point | 285.9 °C (546.6 °F; 559.0 K) |
8.60 g L-1 at 20°C in H2O | |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Moderately Toxic |
GHS labelling: | |
Warning | |
H315, H319, H335 | |
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501 | |
Flash point | 127.9 °C (262.2 °F; 401.0 K) |
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
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Triacetic acid lactone (TAL; [1] 4-hydroxy-6-methyl-2-pyrone) is an organic compound derived enzymatically from glucose. It is a light yellow solid that is soluble in organic solvents.
Triacetic acid lactone consists of two main tautomers.
The tautomer on the left, featuring a 4-hydroxy group, the C4 carbon, is dominant. Triacetic acid lactone is classified as a 2-pyrone compound owing to the ketone group on the C2 carbon in its dominant form.
Triacetic acid lactone is synthesized either from dehydroacetic acid, another 2-pyrone derivative, or from glucose by enzymatic catalysis. In its original synthesis, triacetic acid lactone was obtained by treatment of dehydroacetic acid with sulfuric acid at 135 °C. Dehydroacetic acid undergoes ring-opening and hydration to form "tetracetic acid". [2] Upon cooling, triacetic acid reverts to a lactone ring similar to the dehydroacetic acid structure, and the triacetic acid lactone is recovered by crystallization in cold water.
The microbial synthesis of triacetic acid lactone requires the enzyme 2-pyrone synthase (2-PS). [3] This enzyme has been examined in two hosts Escherichia coli and Saccharomyces cerevisiae. The Saccharomyces cerevisiae host being used during the synthesis produces a higher yield (70%) compared with the Escherichia coli host, which produces a yield of 40% of triacetic acid lactone. This enzyme catalyzes the synthesis of triacetic acid lactone from acetyl-CoA via two subsequent condensations with malonyl-CoA. This produces an intermediate of 3,5-diketohexanoate thioester, which undergoes ring closure to produce triacetic acid lactone.
The lactone is a versatile intermediate in organic synthesis. Substantial negative charge accumulates on the C3 carbon, rendering it nucleophilic, but the C5 carbon is inert. [4]
It has also been described as a platform chemical, meaning that it could be the precursor to other fine chemicals. The lactone undergoes decarboxylation to acetylacetone. It is also a precursor to sorbic acid, dienoic acid, and hexenoic acid. Dienoic acid is used to inhibit the growth of various molds and hexenoic acid is used as a flavoring agent. [5] Acetylacetone is used for metal extraction and plating and as a food additive. [6]