The reactions of IO with HO2, NO and CH3SCH3: Flow tube studies of kinetics and product formation

Abstract

Rate coefficients for the reaction between IO and HO₂ and between IO and NO were obtained using a low-pressure flow tube at total pressures of 1.0–2.0 Torr of He, and between 353 and 273 K. Reactants and products were detected using a quadrupole mass spectrometer. The temperature-dependent rate coefficient for the reaction between IO and HO₂ is described by k₂ = (2.2 ± 0.6) × 10⁻¹¹ exp{(400 ± 80)/T} cm³ s⁻¹. The temperature-dependent rate coefficient for the reaction between IO and NO is described by k₄ = (8.3 ± 2.3) × 10⁻¹² exp{(269 ± 85)/T} cm³ s⁻¹. The rate coefficient at 298 K (and 2.5–2.7 Torr He) for the reaction of IO and CH₃SCH₃ was found to be k₅ = (1.6 ± 0.3) × 10⁻¹⁴ cm³ s⁻¹. At all the temperatures used in this study the only products observed were HOI from reaction (2), NO₂ from reaction (4), and CH₃S(O)CH₃ from reaction (5).

The new results for reactions (2) and (4) are compared to existing measurements, and combined with selected data sets to make recommendations for the temperature-dependent rate coefficients.