Production of radicals in the ozonolysis of propene in air

Radical production in the ozonolysis of propene in air was monitored directly by a peroxy radical chemical amplification (PERCA) instrument at room temperature (298±2 K) and atmospheric pressure (1×10⁵ Pa). The ozonolysis reactions were conducted in a flow tube under pseudo-first-order conditions for ozone. The decay in ozone was calculated based on reaction time t _r and effective rate constant k _eff (k _eff = k ₁[C₃H₆]₀)) for the ozone-propene reaction. The total radical yields relative to consumed ozone were determined to be 0.97±0.17 (σ). A box model was used to simulate radical production in the ozone-propene reaction. The model-derived radical yields agree well with those from experiment within the uncertainty of the two methods. In addition, the yields for OH, HO₂ and CH₃O₂ were obtained from the measured total radical yields and radical partitioning derived from the box model. The yield is 0.39±0.08 (σ) for OH, 0.19±0.04 (σ) for HO₂, and 0.39±0.08 (σ) for CH₃O₂. This work suggests that the previously measured radical yield by indirect method for the ozonolysis of propene may be underestimated.