THE DECOMPOSITION KINETICS OF HYDROGEN PEROXIDE CATALYSED BY ETHYLENEDIAMINE-TETRAKIS(METHYLENEPHOSPHONATO)IRON(III)

Abstract
The catalysed decomposition of hydrogen peroxide in the presence of ethylenediaminetetrakis(methylene-phosphonato)iron(III) was studied at various temperatures. The observed rate law is given by -d[H2O2]/dt = k1K/([H+] + K) [Fe(CENTMP)]. where K is the acid-dissociation constant of the aquo complex. A mechanism involving the aquation of the ternary hydroxo complex as the rate-determining step is suggested. The values of k1 and pK were determined at 35°C to be 0.62 × 10−2 and 10.09 repectively. Activation enthalpy and activation entropy for the aquation reaction were determined from Arrhenius plots and found to be ΔH = 74.57 kJ mol−1 and ΔS = 202 J K−1 mol−1. The results are compared with previously reported data on catalysis by the structurally related [Fe(EDTA)] species.