Reactions of ozone with Br(-), SO(3)(2-), HSO(3)(-), I(-), and NO(2)(-), studied by stopped-flow and pulsed-accelerated-flow techniques, are first order in the concentration of O(3)(aq) and first order in the concentration of each anion. The rate constants increase by a factor of 5 x 10(6) as the nucleophilicities of the anions increase from Br(-) to SO(3)(2-). Ozone adducts with the nucleophiles are proposed as steady-state intermediates prior to oxygen atom transfer with release of O(2). Ab initio calculations show possible structures for the intermediates. The reaction between Br(-) and O(3) is accelerated by H(+) but exhibits a kinetic saturation effect as the acidity increases. The kinetics indicate formation of BrOOO(-) as a steady-state intermediate with an acid-assisted step to give BrOH and O(2). Temperature dependencies of the reactions of Br(-) and HSO(3)(-) with O(3) in acidic solutions are determined from 1 to 25 degrees C. These kinetics are important in studies of annual ozone depletion in the Arctic troposphere at polar sunrise.

The first step in NHzCl oxidation of NOz-is the general acid-assisted formation of nitryl chloride, where km is 7.6 X loe M-2 s-l for H30+ and is 46 M-2 s-l for HzP04-(25.0 "C, p = 0.50 M). This is the rate-limiting step at very low [NHJ and high [NOz-I concentrations: HA + NHzCl+ NOz--A-+ NH3 + NOZC1, where the subsequent reactions of NOzCl are rapid. Under conditions of higher [NH,] and lower [NOz-], the overall rate of loss of NHzCl is suppressed, and a complex rate expression is observed. This rate dependence is derived from an analogous mechanism found for the reaction between OC1-and NOz-:. In this mechanism, NOzCl forms reversibly in the first step (k~'/k-l') and either reacts with a second NOz-(kz) to give Nz04 or loses C1-(k4) to give NOz+; both Nz04 and N02+ hydrolyze rapidly to give NO,-. The relative reaction rate of OC1-+ H+ + NO2-is estimated to be 1.8 X 105 greater than for NH2Cl + H+ + NOz-. An equilibrium formation constant, Kf =[NHZC~]/([NHJ[HOC~I) = 3.8 X 1O1O M-l, is calculated from the kinetic data.

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Kinetics and Mechanisms of Aqueous Ozone Reactions with Bromide, Sulfite, Hydrogen Sulfite, Iodide, and Nitrite Ions. -Stopped-flow and pulsed-accelerated-flow techniques indicate that the reactions of aqueous O 3 with Br − , HSO 3 − , I − , and NO 2 − are first order both in the concentration of O 3 (aq) and the concentration of each anion. Ab initio calculations reveal possible structures of O 3 adducts with the title anions, proposed as steady-state intermediates. Temperature dependencies of the reactions of Br − and HSO 3 − with O 3 in acidic solutions are determined from 1 to 25 • C. These kinetics are important in studies of annual ozone depletion in the Arctic troposphere at polar sunrise. -(LIU, QIAN; SCHURTER, LYNN M.; MULLER, CHARLES E.; ALOISIO, SIMONE; FRANCISCO, JOSEPH S.; MARGERUM, DALE W.; Inorg.