A pulse radiolysis study of the oxidation of Br– by Cl2˙– in aqueous solution: formation and properties of ClBr˙–

Abstract

The oxidation of Br À by Cl 2 À is investigated by pulse radiolysis in aqueous solutions of NaCl and NaBr. Depending on the ratio of the concentration of Br À to Cl À , the main product being observed is either Cl 2 À , ClBr À or Br 2 À . The mixed radical anion ClBr À exhibits a broad absorption band at 350 nm with e 350 ¼ 9300 dm 3 mol À1 cm À1 . The rate constants of the equilibrium Cl 2 À + Br À Ð ClBr À + Cl À are determined to be k f ¼ 4 Â 10 9 and k b ¼ 1.1 Â 10 2 dm 3 mol À1 s À1 .

Photoinduced oxidation of sea salt halides by aromatic ketones: a source of halogenated radicals

“…After 8 µs when the triplet benzophenone is relaxed, the absorption at 350 nm is still apparent and long-lived (with a lifetime of ca. 15±0.5 µs) and may correspond to bromine radical anion Br •− 2 (Ershov and Janata, 2003;Ershov et al, 2002;Grodkowski and Neta, 2002;Hurley et al, 1988;Zehavi and Rabani, 1972). This radical anion is known to absorb light from 300 to 400 nm with maximum absorption at 355 nm.…”

“…Indeed, in mixed chloride-bromide solutions, it appears that the quenching of 3 BP is dominated by the bromide anion, as inferred from the rapid deactivation rate. In this case, the mechanism of Br 2 and BrCl formation may occur via (Ershov et al, 2002).…”

Photochemistry of the IrCl6 2− complex in aqueous solutions in the presence of the bromide anions

“…Another possible way of formation of the di halide radical anion upon photolysis of IrCl 6 2-in the pres ence of bromide ions is associated with the abstraction of the chlorine atom of the secondary radical pair by the Brion. In this case, the photolysis mechanism involves reac tions (1)-(3) that proceed in the absence of Br -and reac tions (21) and (22) …”

Pulse radiolysis study of I− oxidation with radical anions Cl2 ⋅− in an aqueous solution

“…6 The potential of the ClBr •-/Cl • , Br -pair is 1.85 V. 3 A com parison of E°(Cl 2 •-/2 Cl -) with E°(I 2 •-/2 I -) = 1.03 V and E°(I • /I -) = 1.33 V 6 suggests that the radical anions Cl 2 •-can oxidize the I -ions. However, this reaction remained unstudied to date.…”

“…For instance, the absorption band maximum (λ max ) in its spectrum lies at 350 nm, and the molar absorption coefficient (ε) is 9.3•10 3 L mol -1 cm -1 . 3 The corresponding parameters for Cl 2 •-are 340 nm and 8.8•10 3 L mol -1 cm -1 , 4 and those for Br 2 •-are 360 nm and 9.9•10 3 L mol -1 cm -1 . 5 The stan dard redox potentials (E°) for the Cl 2…”