DQFA-Artículos
URI permanente para esta colecciónhttps://hdl.handle.net/10953/276
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Examinando DQFA-Artículos por Autor "Azofra, Luis Miguel"
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Ítem Conformational preference and chiroptical response of Carbohydrates D-Ribose and 2-Deoxy-D-ribose in aqueous and solid phases(American Chemical Society, 2013) Quesada-Moreno, María del Mar; Azofra, Luis Miguel; Avilés-Moreno, Juan Ramón; Alkorta, Ibon; Elguero, José; López-González, Juan JesúsThis work targets the structural preferences of D-ribose and 2-deoxy-D-ribose in water solution and solid phase. A theoretical DFT (B3LYP and M06-2X) and MP2 study has been undertaken considering the five possible configurations (open-chain, α-furanose, β-furanose, α-pyranose, and β-pyranose) of these two carbohydrates with a comparison of the solvent treatment using only a continuum solvation model (PCM) and the PCM plus one explicit water molecule. In addition, experimental vibrational studies using both nonchiroptical (IR-Raman) and chiroptical (VCD) techniques have been carried out. The theoretical and experimental results show that α-and β-pyranose forms are the dominant configurations for both compounds. Moreover, it has been found that 2-deoxy-D-ribose presents a non-negligible percentage of open-chain forms in aqueous solution, while in solid phase this configuration is absent.Ítem Understanding the Aldo-Enediolate Tautomerism of Glycolaldehyde in Basic Aqueous Solutions(Wiley, 2015) Azofra, Luis Miguel; Quesada-Moreno, María del Mar; Alkorta, Ibon; Avilés-Moreno, Juan Ramón; Elguero, José; López-González, Juan JesúsThe 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.