Kinetics of Electron Exchange between Bromopyrogallol Red and Periodate Ion in Aqueous Acidic Medium

The kinetics of the electron transfer reaction between Bromopyrogallol (BPR2-) and periodate ion in aqueous acidic solution has been studied in the acid range 0.1 — 10-4 ≤ [H+] ≤ 2 — 10-4 mol dm-3, ionic strength 0.01 ≤ [I] ≤ 0.18 mol dm-3 (NaCl) and T = 29 ± 1.ºC. The reaction shows a first order dependence on reductant and half order on oxidant concentration respectively. It displayed an inverse dependence on the acid concentration of the reaction medium. The reaction conforms to the rate law: -d[BPR2-]/dt = k2[BPR2-][IO4-]1/2[H+]-1/2 The stoichiometry of the reaction is 1:1. Added anions had no effect on the rate of the reaction. Spectroscopic investigation indicates that an intermediate complex is probably formed in the course of this reaction. The reaction is believed to proceed via the innersphere mechanistic pathway.