title: Observation of the keto tautomer of D-fructose in D(2)O using (1)H NMR spectroscopy.
abstract: D-Fructose was analysed by NMR spectroscopy and previously unidentified (1)H NMR resonances were assigned to the keto and α-pyranose tautomers. The full assignment of shifts for the various fructose tautomers enabled the use of (1)H NMR spectroscopy in studies of the mutarotation (5-25°C) and tautomeric composition at equilibrium (5-50°C). The mutarotation of β-pyranose to furanose tautomers in D(2)O at a concentration of 0.18 M was found to have an activation energy of 62.6 kJmol(-1). At tautomeric equilibrium (20°C in D(2)O) the distribution of the β-pyranose, β-furanose, α-furanose, α-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.
authors: School of Chemical and Physical Sciences, Flinders University, Adelaide 5042, Australia. thomas.barclay@flinders.edu.au
authors: Thomas
authors: T
authors: Barclay
authors: Milena
authors: M
authors: Ginic-Markovic
authors: Martin R
authors: MR
authors: Johnston
authors: Peter
authors: P
authors: Cooper
authors: Nikolai
authors: N
authors: Petrovsky
mesh_terms: D017666:Deuterium Oxide / Q000737:chemistry*; D005632:Fructose / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*
chemical_list: D005632:Fructose; D017666:Deuterium Oxide