The Oscillatory Briggs-Rauscher Reaction. 1. Examination of Subsystems

Article abstract of DOI:10.1021/ja00365a009

In acidic aqueous solution at 25 deg C, only slow or nonexistent reaction is observed for any two of three species iodate ion, hydrogen peroxide, and manganous ion.However, if all three species are present, 0.002 M Mn²⁺ catalyzes the iodate oxidation of peroxide at a rate almost 1000 times that in the absence of a catalyst! This remarkable observation, which has already been reported by Cooke, can be explained by postulating that the radical oxidant *IO2 is very sluggish at abstracting hydrogen atoms from the species like H2O2 but can oxidize Mn²⁺ by electron transfer.A detailed mechanism has been proposed that models semiquantitatively not only the manganous catalyzed iodate oxidation of peroxide but also the simultaneous induced disproportionation of the peroxide and the fact that the concentration of elementary iodine does not increase to a limiting value but rises to a maximum and then decreases toward a small value.Despite this single extremum, the subsystem does not exhibit oscillatory behavior.