Rate coefficients for the reactions of chlorine atoms with methanol and

Rate coefficients have been measured for the reactions of Cl atoms with methanol (k₁) and acetaldehyde (k₂) using both absolute (laser photolysis with resonance fluorescence) and relative rate methods at 295 ± 2 K. The measured rate coefficients were (units of 10^-11 cm³ molecule^-1 s^-1): absolute method, k₁ = (5.1 ± 0.4). k₂ = (7.3 ±0.7); relative method k₁ = (5.6 ±0.6), k₂ = (8.4 ±1.0). Based on a critical evaluation of the literature data, the following rate coefficients are recommended: k₁ = (5.4 ±0.9) × 10^-11 and k₂ = (7.8 ±1.3) × 10^-11 cm³ molecule^-1 s^-1 (95% confidence limits). The results significantly improve the confidence in the database for reactions of Cl atoms with these oxygenated organics. Rate coefficients were also measured for the reactions of Cl₂ with CH₂OH, k₅ = (2.9 ±0.6) × 10^-11 and CH₃CO, k₆ = (4.3 ±1.5) × 10^-11 cm³ molecule^-1 s^-1. by observing the regeneration of Cl atoms in the absence of O₂. Based on these results and those from a previous relative rate study, the rate coefficient for CH₃CO + O₂ at the high pressure limit is estimated to be (5.7 ±1.9) × 10^-12 cm³ molecule^-1 s^-1.