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| Names | |
|---|---|
| Preferred IUPAC name Hydroxyacetaldehyde | |
| Systematic IUPAC name Hydroxyethanal | |
| Other names 2-Hydroxyacetaldehyde 2-Hydroxyethanal | |
| Identifiers | |
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3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
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| ECHA InfoCard | 100.004.987 |
| KEGG |
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| UNII | |
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| Properties | |
| C2H4O2 | |
| Molar mass | 60.052 g/mol |
| Density | 1.065 g/mL |
| Melting point | 97 °C (207 °F; 370 K) |
| Boiling point | 131.3 °C (268.3 °F; 404.4 K) |
| Related compounds | |
Related aldehydes | 3-Hydroxybutanal |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Glycolaldehyde is theorganic compound with the formulaHOCH2−CHO. It is the smallest possible molecule that contains both analdehyde group (−CH=O) and ahydroxyl group (−OH). It is a highlyreactive molecule that occurs both in thebiosphere and in theinterstellar medium. It is normally supplied as a white solid. Although it conforms to the general formula forcarbohydrates,Cn(H2O)n, it is not generally considered to be a saccharide.[1]
Glycolaldehyde as a gas is a simple monomeric structure. As a solid and molten liquid, it exists as adimer. Collins and George reported the equilibrium of glycolaldehyde in water by usingNMR.[2][3] In aqueous solution, it exists as a mixture of at least four species, which rapidly interconvert.[4]
In acidic or basic solution, the compound undergoes reversibletautomerization to form 1,2-dihydroxyethene.[5]
It is the only possiblediose, a 2-carbonmonosaccharide, although a diose is not strictly a saccharide. While not a truesugar, it is the simplest sugar-related molecule.[6] It is reported to tastesweet.[7]
Glycolaldehyde is the second most abundant compound formed when preparingpyrolysis oil (up to 10% by weight).[8]
Glycolaldehyde can be synthesized by the oxidation ofethylene glycol usinghydrogen peroxide in the presence ofiron(II) sulfate.[9]
It can form by action ofketolase onfructose 1,6-bisphosphate in an alternate glycolysis pathway. This compound is transferred bythiamine pyrophosphate during thepentose phosphate shunt.
Inpurine catabolism,xanthine is first converted tourate. This is converted to5-hydroxyisourate, which decarboxylates toallantoin andallantoic acid. After hydrolyzing oneurea, this leavesglycolureate. After hydrolyzing the second urea, glycolaldehyde is left. Two glycolaldehydes condense to formerythrose 4-phosphate,[citation needed] which goes to the pentose phosphate shunt again.
Glycolaldehyde is an intermediate in theformose reaction. In the formose reaction, twoformaldehyde molecules condense to make glycolaldehyde. Glycolaldehyde then is converted toglyceraldehyde, presumably via initial tautomerization.[10] The presence of this glycolaldehyde in this reaction demonstrates how it might play an important role in the formation of the chemical building blocks of life.Nucleotides, for example, rely on the formose reaction to attain its sugar unit. Nucleotides are essential for life, because they compose the genetic information and coding for life.
It is often invoked in theories ofabiogenesis.[11][12] In the laboratory, amino acids[13] and short dipeptides[14] have been shown to catalyze the formation of complex sugars from glycolaldehyde. For example, L-valyl-L-valine was used as a catalyst to form tetroses from glycolaldehyde. Theoretical calculations have additionally shown the feasibility of dipeptide-catalyzed synthesis of pentoses.[15] This formation showed stereospecific, catalytic synthesis of D-ribose, the only naturally occurring enantiomer of ribose. Since the detection of this organic compound, many theories have been developed related various chemical routes to explain its formation in stellar systems.
It was found that UV-irradiation of methanol ices containing CO yielded organic compounds such as glycolaldehyde andmethyl formate, the more abundant isomer of glycolaldehyde. The abundances of the products slightly disagree with the observed values found in IRAS 16293-2422, but this can be accounted for by temperature changes.Ethylene Glycol and glycolaldehyde require temperatures above 30 K.[16][17] The general consensus among the astrochemistry research community is in favor of the grain surface reaction hypothesis. However, some scientists believe the reaction occurs within denser and colder parts of the core. The dense core will not allow for irradiation as stated before. This change will completely alter the reaction forming glycolaldehyde.[18]
The different conditions studied indicate how problematic it could be to study chemical systems that are light-years away. The conditions for the formation of glycolaldehyde are still unclear. At this time, the most consistent formation reactions seems to be on the surface of ice incosmic dust.
Glycolaldehyde has been identified in gas and dust near the center of theMilky Way galaxy,[20] in a star-forming region,[21] and around aprotostellar binary star,IRAS 16293-2422, 400 light years from Earth.[22][23] Observation of in-falling glycolaldehyde spectra 60 AU from IRAS 16293-2422 suggests that complex organic molecules may form in stellar systems prior to the formation of planets, eventually arriving on young planets early in their formation.[17]
The interior region of adust cloud is known to be relatively cold. With temperatures as cold as 4 Kelvin, the gases within the cloud will freeze and fasten themselves to the dust, which provides the reaction conditions conducive for the formation of complex molecules such as glycolaldehyde. When a star has formed from the dust cloud, the temperature within the core will increase. This will cause the molecules on the dust to evaporate and be released. The molecule will emit radio waves that can be detected and analyzed.[24] Glycolaldehyde was firstidentified in interstellar space in 2000.[20]
On October 23, 2015, researchers at theParis Observatory announced the discovery of glycolaldehyde andethyl alcohol onComet Lovejoy, the first such identification of these substances in a comet.[25][26]
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