Kinetics and mechanism of oxidation of D-xylose and L-arabinose by chromium(VI) ions in perchloric acid medium

The kinetics of oxidation of D-Xylose and L-Arabinose by Cr(VI) ions in perchloric acid medium have been investigated spectrophotometrically under pseudo-first-order conditions. The reactions exhibit first-order rate dependence each on the substrate and oxidant. The order with respect to [H+] is unity while no effect on the reaction rate is found with respect to the ionic strength. The Arrhenius (Ea) and thermodynamic activation parameters (ΔH≠, ΔS≠ and ΔG≠) are evaluated and the reaction mechanism is interpreted in terms of formation of a 1:1 intermediate complex between a protonated chromic acid molecule and a neutral sugar molecule in sharp contrast to the results of our earlier studies on the C6 and C12 sugars