Kinetics of Oxygen Exchange in the System BrO ‐ H₂O (D₂O)

The kinetics of oxygen exchange between water (H 2 O, D 2 O) and 18 O‐labelled bromate ion has been investigated over the range of 1.7 ≤ pH ≤ 14.3 and 20 ≤ °C ≤ 95. At 60° and ionic strength I ≃ 1.0M (NaNO 3 ), the experimental results were consistent with the rate laws ( R in moll −1 s −1 ): From the temperature dependence of the rate constants the activation parameters Δ H ≠ , Δ S ≠ and ΔC ≠ were derived. In the acid‐catalysed region the form of the rate law and the direction of the solvent isotope effect were the same as previously found, but the numerical values of ΔH ≠ and k 2H / k 2D differ considerably. For the spontaneous and the OH − ‐catalysed exchange reactions bimolecular displacement mechanisms are proposed.