Quantum molecular dynamics study of the reaction of O ₂ with HOCO

The reaction of O ₂ with HOCO has been studied by using an ab initio direct dynamics method based on the UB3PW91 density functional theory. Results show that the reaction can occur via two mechanisms: direct hydrogen abstraction and an addition reaction through a short-lived HOC(O)O ₂ intermediate. The lifetime of the intermediate is predicted to be 660 ±30 fs. Although it is an activated reaction, the activation energy is only 0.71 kcal/mol. At room temperature, the obtained thermal rate coefficient is 2.1 × 10 ^-12 cm ³ molecule ^-1 s ^-1, which is in good agreement with the experimental results.