An FTIR study of the Cl‐atom‐initiated reaction of glyoxal

The kinetics and mechanism of Cl‐atom‐initiated reactions of CHOCHO were studied using the FTIR detection method to monitor the photolysis of Cl 2 –CHOCHO mixtures in 700 torr of N 2 –O 2 diluent at 298 ± 2 K. The observed product distribution in the [O 2 ] pressure of 0–700 torr combined with relative rate measurements provide evidence that: (1) the primary step is Cl + CHOCHO → HCl + CHOCO with a rate constant of [3.8 ± 0.3(σ)] × 10 −11 cm 3 molecule −1 s −1 ; (2) the primary product CHOCO unimolecularly dissociates to CHO and CO with an estimated lifetime of ≤ca. 1 × 10 −7 s; (3) alternatively, the CHOCO reacts with O 2 leading to the formation of CO, CO 2 , and most likely the HO radical, but no stable products containing two carbon atoms; (4) the HO 2 radical, formed in the secondary reaction CHO + O 2 → HO 2 + CO, reacts with the CHOCHO with a rate constant ca. 5 × 10 −16 cm 3 molecule −1 s −1 to form HCOOH and a new transient product resembling that detected previously in the HO 2 reaction with HCHO.