Understanding the Aldo-Enediolate Tautomerism of Glycolaldehyde in Basic Aqueous Solutions
The 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...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Universidad de Jaén |
| Repositorio: | RUJA. Repositorio Institucional de la Producción Científica de la Universidad de Jaén |
| OAI Identifier: | oai:ruja.ujaen.es:10953/4567 |
| Acceso en línea: | https://hdl.handle.net/10953/4567 |
| Access Level: | acceso abierto |
| Palabra clave: | Hydrogen bonds Quantum chemical calculations Raman spectroscopy Solvents Tautomerism |
| Sumario: | The 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 the 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, i.e. 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 the increase of aldehyde species, as 2-oxoethan-1-olate, and the decrease of hydrated aldehyde and dimeric forms. The theoretical ratio ~1.5:1 aldehyde:Z-enediolate reproduces the experimental Raman spectrum in basic medium, with the additional contribution of the previously mentioned ratio between hydrated aldehyde and dimeric forms. Finally, Raman spectroscopy allowed us to monitor the enolization of this carbohydrate model and to conclude that the aldo-enediol tautomerism, formally aldo-enediolate, happens when a suitable amount of basic species is added. |
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