Kinetics and Mechanism of the Chlorate-Bromide Reaction

Rafaela T P Sant'Anna; Roberto B Faria

doi:10.1021/acs.inorgchem.5b01857

Kinetics and Mechanism of the Chlorate-Bromide Reaction

Inorg Chem. 2015 Nov 2;54(21):10415-21. doi: 10.1021/acs.inorgchem.5b01857. Epub 2015 Oct 15.

Authors

Rafaela T P Sant'Anna¹, Roberto B Faria¹

Affiliation

¹ 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.

PMID: 26467822
DOI: 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 fifth-order rate law was found: (1)/3 d[Br2]/dt = k[ClO3(-)][Br(-)][H(+)](3) (k = 5.10 × 10(-6) s(-1) L(4) 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.