REDOX REACTIONS OF S2O8= WITH CU(I) AND FE(II) AT THE ROTATING-RING DISK ELECTRODE

The reactions of Cu(I) and Fe(II) with S2O8= were investigated with the rotating ring disk electrode. An electrocatalytic mechanism is proposed and the rate constant for the Cu(I) reaction was evaluated by a digital simulation technique, as k = 3.37 × 106 exp - (3626/RT). Lower rates were found for the Fe(II), S2O8= system including cases when Fe(II) was complexed. The reactions are of interest for redox polymerization, as the radicals generated can initiate polymer formation. The initiation reaction competes with Cu(I) in reacting with SO4⨪ radicals. The corresponding changes in ring and disk currents provide a measure of the relative rate constants. For acrylic acid the rate of reaction of SO4⨪ with Cu(I) was 55 times that of the monomer. For a series of monomers the relative rates of reaction should reflect the monomer reactivity toward the common radical ion. © 1979, The Electrochemical Society, Inc. All rights reserved.