Uttam Pal - pKa Determination of D-Ribose by Raman Spectroscopy

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      Publication Details (including relevant citation   information):

      Sen, Sudeshna, Pal, Uttam, Maiti, Nakul Chandra -

      Abstract: Determination of pKa of OH groups   present in D-ribose is crucial in order to elucidate the origin   and mechanism of many catalytic processes that involve the ribose   unit. However, there is hardly any report about the experimental   pKa of the OH group due to lack of appropriate method. In this   study we have investigated the protonation state of OH groups in   D-ribose by introducing C-D labeling and measuring the changes in   the isolated C-D frequency in several isotopologues of the   compound with pH. The large shift in the ?C D of D ribose C1 D in   ionized condition compared to other deuterium substituted   D-riboses (e.g. D-ribose-C2-D, D-ribose-C3-D etc.) confirmed that   C1 OH group preferred ionization and the ionization pKa was 11.8.   Both the ionized and unionized structures of D-ribose preferred   pyranose conformation, which was supported by 13C NMR   experiments. Electronic redistribution via resonance and   intra-molecular hydrogen bond formation were proposed to account   for the stabilization of the ionized structure.

      Address (URL): http://dx.doi.org/10.1021/jp4092392