Kinetics and mechanism of the reaction of OH with ClO

The kinetics and mechanism of the following reactions have been studied in the temperature range 230–360 K and at total pressure of 1 Torr of helium, using the discharge‐flow mass spectrometric method: 1a : 1b : The following Arrhenius expression for the total rate constant was obtained from the kinetics of OH consumption in excess of ClO radical, produced in the Cl + O3 reaction either in excess of Cl atoms or ozone: k1 = (6.7 ± 1.8) × 10−12 exp {(360 ± 90)/T} cm3 molecule−1 s−1 (with k1 = (2.2 ± 0.4) × 10−11 cm3 molecule−1 s−1 at T = 298 K), where uncertainties represent 95% confidence limits and include estimated systematic errors. The value of k1 is compared with those from previous studies and current recommendations. HCl was detected as a minor product of reaction (1) and the rate constant for the channel forming HCl (reaction (1b)) has been determined from the kinetics of HCl formation at T = 230–320 K: k1b = (9.7 ± 4.1) × 10−14 exp{(600 ± 120)/T} cm3 molecule−1 s−1 (with k1b = (7.3 ± 2.2) × 10−13 cm3 molecule−1 s−1 and k1b/k1 = 0.035 ± 0.010 at T = 298 K), where uncertainties represent 95% confidence limits. In addition, the measured kinetic data were used to derive the enthalpy of formation of HO2 radicals: Δ Hf,298(HO2) = 3.0 ± 0.4 kcal mol−1.