Kinetics and product studies of the reaction of Br, Cl, and NO with ClOOCl using discharge-flow mass spectrometry

Abstract

The kinetics of the reactions Cl + ClOOCl → products (5), Br + ClOOCl → products (7), and NO + ClOOCl → products (8) have been studied as a function of temperature at 1 Torr total pressure using a discharge-flow mass spectrometric technique. The measured rate coefficients, expressed in Arrhenius form, are k₅ = (7.60 ± 0.56) × 10⁻¹¹exp((65.4 ± 17.9)/T) cm³ s⁻¹ for 217 K < T < 298 K, and k₇ = (5.88 ± 0.50) × 10⁻¹² exp(−173 ± 20/T) cm³ s⁻¹ for 223 K < T< 298 K. The observed temperature dependencies of these rate coefficients indicate a common direct halogen atom abstraction mechanism. Mass spectral product studies indicate that BrCl is the only major Br-containing product from reaction (7). Extensive product studies were used to estimate that the peroxide form of the ClO-dimer is formed in >90% yield from the ClO self-reaction. No evidence for the formation of ClOClO and ClClO₂ was observed. No reaction between NO and ClOOCl was observed and an upper limit of k₈ < 1 × 10⁻¹⁵ cm³ s⁻¹ for 220 K < T< 298 K was determined.