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Título

Understanding the Aldo-Enediolate Tautomerism of Glycolaldehyde in Basic Aqueous Solutions

AutorAzofra, Luis Miguel; Quesada-Moreno, María Mar; Alkorta, Ibon ; Avilés-Moreno, Juan Ramón; Elguero, José ; López-González, Juan Jesús
Palabras claveTautomerism
Raman spectroscopy
Solvents
Quantum chemical calculations
Hydrogen bonds
Fecha de publicación2015
EditorJohn Wiley & Sons
CitaciónChemphyschem : a European journal of chemical physics and physical chemistry 16: 2226-2236 (2015)
ResumenThe biochemically important interconversion process between aldoses and ketoses is assumed to take place via 1,2-enediol or 1,2-enediolate intermediates, but such intermediates have never been isolated. The current work was undertaken in an attempt to detect the presence of the 1,2-enediol structure of glycolaldehyde in alkaline medium, actually a 1,2-enediolate, and to try to clarify the scarce data existing about both the formation of deprotonated enediol and the aldo-enediolate equilibrium. The Raman spectra of neutral and basic solutions were recorded as a function of time for eleven days. Several bands associated with the presence of the enediolate were observed in alkaline medium. Glycolaldehyde exists as three different structures in aqueous solution at neutral pH, that is, hydrated aldehydes, aldehydes and dimers, with a respective ratio of approximately 4:0.25:1. Additionally, the formation of Z-enediolate forms takes place at basic pH, together with an increase in the concentration of aldehyde species, such as 2-oxoethan-1-olate, and a decrease in the concentrations of the hydrated aldehyde and dimeric forms. The theoretical ratio of ≈1.5:1 for aldehyde:Z-enediolate reproduces the experimental Raman spectrum in basic medium, with an additional contribution of the previously mentioned ratio between the hydrated aldehyde and dimeric forms. Finally, Raman spectroscopy allowed us to monitor the enolization of this carbohydrate model and conclude that aldo-enediol tautomerism - formally aldo-enediolate - happens when a suitable amount of basic species is added.
Versión del editorhttp://dx.doi.org/10.1002/cphc.201500139
URIhttp://hdl.handle.net/10261/136350
DOI10.1002/cphc.201500139
Identificadoresdoi: 10.1002/cphc.201500139
issn: 1439-4235
e-issn: 1439-7641
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