Mutarotation in biologically important pure L-fucose and its enantiomer.

The sugar specific mutarotation reaction in biologically important L-fucose and its enantiomer in the pure, anhydrous, supercooled liquid state has been studied. Kinetics measurements in the temperature range 313-328 K at ambient pressure have been performed by means of dielectric spectroscopy, a method widely used for studying the molecular dynamics of glass-forming liquids. The kinetic curves have been obtained by tracking the equilibration process in sugar melted and quenched to the desired temperature. Thereafter, an activation energy equal to Ea = 140 kJ mol(-1) for D-fucose and Ea = 123 kJ mol(-1) for L-fucose has been derived from the Arrhenius fit of temperature dependent rate constants. It was also shown that the kinetics curves at the lowest temperatures studied have sigmoidal shape, which was connected to the high concentration of furanosidic forms.