KINETICS AND MECHANISM OF OXIDATION OF D-FRUCTOSE AND L-SORBOSE BY CHROMIUM(VI) AND VANADIUM(V) IN PERCHLORIC ACID MEDIUM

Article abstract of DOI:10.1016/S0008-6215(00)80520-0

Kinetic data for the oxidation of D-fructose and L-sorbose by chromium(VI) and vanadium (V) in perchloric acid medium are reported.The addition of perchloric acid and sodium perchlorate increases the pseudo-first-order rate constants.Change of the reaction from medium from water to deuterium oxide appreciably affects the rates of chromium(VI) oxidations, but does not affect those of vanadium(V) oxidations.The activation parameters are ΔH⁺⁺ = 46.6 +/- 3.4 ( fructose ) and 50.6 +/- 6.3 ( sorbose ) kJ*mol^-1,and ΔS= -105 +/- 11 ( fructose ) and -100 +/- 20 ( sorbose ) J*deg^-1*mol^-1 for chromium(VI) oxidations, and for the other reactions, ΔH= 53.2 +/- 4.2 ( fructose ) and 52.3 +/- 6.3 ( sorbose ) kJ*mol^-1, and ΔS= -139.0 +/- 14 ( fructose ) and -137 +/- 20 ( sorbose ) J*deg^-1*mol^-1.The kinetics of the oxidations of ketohexoses by chromium(VI) indicate no intermediate-complex formation, whereas those for vanadium(V) indicate the formation of a 1:1 intermediate complex between ketohexoses and vanadium(V).