The effect of chloride ions on the kinetics and mechanism of the copper-catalysed oxidation of ascorbic acid by dissolved oxygen has been examined over the pH range 2.0-3.5 and chloride concentrations up to 0.2 mol dm-3. The empirical rate law has been established as - d[O2]/dt = kobs.[O2]1/2 over the whole range. At constant total ascorbate, total copper, and hydrogen ion concentrations, the general relationship (1) was obtained. The constants kobs. = A + B[Cl-]/C + D[Cl-] + E[Cl-]2 (1) A to E were evaluated using data obtained in pure nitrate media to fix A and C, and the dependence of all the constants on pH, total copper concentration, and total ascorbate concentrations established experimentally. It is also pointed out that a mechanism based on the involvement of copper(I) rather than the copper(III) invoked by us cannot be entirely ruled out.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|State||Published - Dec 1 1982|
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