KINETIC STUDY OF THE HYDROGEN PEROXIDE REACTION WITH THE 1-HYDROXYETHYLIDENE-1,1-DIPHOSPHONATOIRON(III) COMPLEX

The rate of reaction of [Fe(HEDP)] with H2O2 in 0.10 M KNO3 solution was investigated at various temperatures. The observed rate law is given by the expression where k1 and k2 are the rate constants in the presence of [FeHL−] and [FeL2-] complex species, respectively, and K1 is the ionisation constant of [FeHL−]. The rate constants k1 and k2 were determined at 30°C to be 0.024 ± 0.002 and 0.189 ± 0.005 M−1s−1, respectively. The corresponding activation enthalpies (ΔH1 = 73.8 ± 10.5 and ΔH2 = 58.9 ± 0.8 kJ mol−1) and activation entropies (ΔS1 = −33 ± 33 and ΔS2 = −64 ± 2 J K−1 mol−1) were calculated from a least-squares fit to Arrhenius plots. The results are compared with previously reported data for other complexes.