Role of trace metal ions. Kinetics and mechanism of the copper(II)-catalysed oxidation of ascorbic acid with peroxodiphosphate in acetate buffers
Abstract
The reaction between peroxodiphosphate and ascorbic acid (H2A) in acetate buffers is essentially catalysed by trace metal-ion impurities of CuII and FeIII present in the reagents. Copper(II) has an about ten times larger catalytic activity than FeIII, and the activity is so specific and precise that one can calculate the amount of CuII present in a system as an impurity, from the initial rates of ‘uncatalysed’ reactions. The reactions in the absence and presence of copper(II) have the same characteristics. The rate law (i) is obeyed for the catalysed reaction, where K1d and K2d are