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: 1a$$\hbox{OH} + \hbox{ClO} \rightarrow \hbox{Cl} + \hbox{HO}_2$$1b: 1b$$\hbox{OH} + \hbox{ClO} \rightarrow \hbox{HCl} + \hbox{O}_2$$ 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 + O 3 reaction either in excess of Cl atoms or ozone: k 1 = (6.7 ± 1.8) × 10 −12 exp {(360 ± 90)/T} cm 3 molecule −1 s −1 (with k 1 = (2.2 ± 0.4) × 10 −11 cm 3 molecule −1 s −1 at T = 298 K), where uncertainties represent 95% confidence limits and include estimated systematic errors. The value of k 1 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: k 1b = (9.7 ± 4.1) × 10 −14 exp{(600 ± 120)/T} cm 3 molecule −1 s −1 (with k 1b = (7.3 ± 2.2) × 10 −13 cm 3 molecule −1 s −1 and k 1b / k 1 = 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 HO 2 radicals: Δ H f,298 (HO 2 ) = 3.0 ± 0.4 kcal mol −1 . © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 587–599, 2001