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Concept
Glycolaldéhyde
Résumé
Glycolaldehyde is the organic compound with the formula . It is the smallest possible molecule that contains both an aldehyde group () and a hydroxyl group (). It is a highly reactive molecule that occurs both in the biosphere and in the interstellar medium. It is normally supplied as a white solid. Although it conforms to the general formula for carbohydrates, , it is not generally considered to be a saccharide.
Glycolaldehyde as a gas is a simple monomeric structure. As a solid and molten liquid, it exists as a dimer. Collins and George reported the equilibrium of glycolaldehyde in water by using NMR. In aqueous solution, it exists as a mixture of at least four species, which rapidly interconvert.
In acidic or basic solution, the compound undergoes reversible tautomerization to form 1,2-dihydroxyethene.
It is the only possible diose, a 2-carbon monosaccharide, although a diose is not strictly a saccharide. While not a true sugar, it is the simplest sugar-related molecule. It is reported to taste sweet.
Glycolaldehyde is the second most abundant compound formed when preparing pyrolysis oil (up to 10% by weight).
Glycolaldehyde can be synthesized by the oxidation of ethylene glycol using hydrogen peroxide in the presence of iron(II) sulfate.Hans Peter Latscha, Uli Kazmaier und Helmut Alfons Klein : Organic Chemistry: Chemistry Basiswissen-II '. Springer, Berlin; 6, vollständig überarbeitete Auflage 2008, , S. 217
It can form by action of ketolase on fructose 1,6-bisphosphate in an alternate glycolysis pathway. This compound is transferred by thiamine pyrophosphate during the pentose phosphate shunt.
In purine catabolism, xanthine is first converted to urate. This is converted to 5-hydroxyisourate, which decarboxylates to allantoin and allantoic acid. After hydrolyzing one urea, this leaves glycolureate. After hydrolyzing the second urea, glycolaldehyde is left. Two glycolaldehydes condense to form erythrose 4-phosphate, which goes to the pentose phosphate shunt again.
Glycolaldehyde is an intermediate in the formose reaction.
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