Kinetics of oxidation of N,N'-ethylenebis(isonitrosoacetylacetoneimine)copper(II) by peroxydisulfate in aqueous acidic solutions

摘要

Peroxydisulfate (PDS) oxidizes N,N'-ethylene-bis(isonitrosoacetyleacetoneimine)copper(II) complex, Cu~(II)L, to the corresponding copper(III) complex, [Cu~(III)L]~+. The kinetic runs were performed in the presence of EDTA to scavenge any trace metal impurities. The kinetics of the reaction at constant pH, ionic strength, and temperature obeys the rate law d[Cu~(III)L]/dt = 2k2[Cu~(II)L][S2O_8~(2-)] with k2 having a value of (8.85 ± 0.32) x 10~(-2) M~(-1) s~(-1) at μ = 0.30 M and T = 25.0 °C. The rate constant k2 is not affected by variation of pH over the range 3.60-5.20. The second order rate constant is also unaffected by changing ionic strength. The values of k_(obs) were determined over the temperature 25.0-40.0 °C range. The enthalpy of activation, ΔH*, and entropy of activation, ΔS*, have been calculated as 34.9 ± 0.5 kJ mol~(-1) and -173.3 ± 11.4 J K~(-1) mol~(-1), respectively. The kinetics of this reaction, as far as we know, is the first evidence that copper(III) is the likely reactive species in copper catalyzed PDS oxidation reactions.