Kinetics of the uncatalysed and silver(I)-catalysed oxidation of hydrogen peroxide by [ethylenebis(biguanide)]silver(III) ion in acid perchlorate media

Banerjee, Rupendranath ; Das, Amitava ; Dasgupta, Subrata (1989) Kinetics of the uncatalysed and silver(I)-catalysed oxidation of hydrogen peroxide by [ethylenebis(biguanide)]silver(III) ion in acid perchlorate media Journal of the Chemical Society Dalton Transactions, 1989 (9). pp. 1645-1649. ISSN 1472-7773

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Official URL: http://pubs.rsc.org/en/content/articlelanding/1989...

Related URL: http://dx.doi.org/10.1039/DT9890001645

Abstract

In aqueous acid media [ethylenebis(biguanide)]silver(III) oxidises H2O2 to O2, itself being reduced to AgI and ethylenebis(biguanide): a 1 : 1 stoicheiometry has been established. The reaction is catalysed by Ag+ and the empirical rate law is -d[complex]/dt=(kuncat+kcat[Ag+])[H2O2][complex]/[H+]. At 30 °C and /= 1.0 mol dm-3, kuncat=(6.5 ± 0.5)× 10-5 s-l and kcat=(9 ± 1)× 10-4 dm3 mol-1 s-1. For kuncat, ΔH= 31 ± I2 kJ mol-1 and ΔS=-222 ± 37 J K-1mol-1, while for kcat the values are 41 ± 16 kJ mol-1 and -167 ± 53 J K-1 mol-1 respectively. The inverse proton dependence of the rate arises from deprotonation of H2O2 facilitated by its axial co-ordination to the complex, forming an adduct; catalysis by AgI arises through complexation of Ag1 with this adduct. The probable mechanism and plausible role of any intermediate silver(II) species are discussed.

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