Observation of the keto tautomer of D-fructose in D2O using 1H NMR spectroscopy
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Date
2012
Authors
Barclay, T.G.
Ginic Markovic, M.
Johnston, M.
Cooper, P.
Petrovsky, N.
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Carbohydrate Research, 2012; 347(1):136-141
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Abstract
D-Fructose was analysed by NMR spectroscopy and previously unidentified 1H NMR resonances were assigned to the keto and a-pyranose tautomers. The full assignment of shifts for the various fructose tautomers enabled the use of 1H NMR spectroscopy in studies of the mutarotation (5-25 C) and tautomeric composition at equilibrium (5-50 C). The mutarotation of b-pyranose to furanose tautomers in D2O at a concentration of 0.18 M was found to have an activation energy of 62.6 kJ mol 1. At tautomeric equilibrium (20 C in D2O) the distribution of the b-pyranose, b-furanose, a-furanose, a-pyranose and the keto tautomers was found to be 68.23%, 22.35%, 6.24%, 2.67% and 0.50%, respectively. This tautomeric composition was not significantly affected by varying concentrations between 0.089 and 0.36 M or acidification to pH 3. Upon equilibrating at 6 temperatures between 5 and 50 C there was a linear relationship between the change in concentration and temperature for all forms.
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Data source: Supplementary data, http://www.sciencedirect.com.access.library.unisa.edu.au/science/article/pii/S0008621511005404
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Crown copyright 2011. Published by Elsevier.