Kinetics and Mechanism of the Chlorate−Bromide Reaction

Kinetics and Mechanism of the Chlorate−Bromide Reaction

Rafaela T. P. Sant’Anna and Roberto B. Faria*

Instituto de Química, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, CT, Bloco A, 21941-611 Rio de Janeiro, RJ Brazil

Inorg. Chem. 2015, 54, 10415-10421.

http://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.5b01857

Abstract:
The chlorate−bromide reaction, ClO3 − + 6Br− + 6H+ → 3Br2 + Cl− + 3H2O, was followed at the Br3 −/Br2 isosbestic point (446 nm). A fifthorder rate law was found: 1 /3 d[Br2]/dt = k[ClO3 −][Br−][H+ ] 3 (k = 5.10 × 10−6 s −1 L4 mol−4 ) at 25 °C and I = 2.4 mol L−1 . At high bromide concentrations, the bromide order becomes close to zero, indicating a saturation profile on bromide concentration, similar to the chloride saturation profile observed in the chlorate−chloride reaction. A mechanism is proposed that considers the formation of the intermediate BrOClO2 2−, similar to the intermediate ClOClO2 2− proposed in the mechanism of the chlorate−chloride reaction.

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