Reactivity of the anti-Criegee intermediate of β-pinene with prevalent atmospheric species

The reaction of the anti-Criegee intermediate (anti-CI) of β-pinene with prevalent atmospheric species has been investigated using quantum-chemical calculations. The calculations predict that the ozone addition to CI occurs with a Gibbs energy of activation (ΔG‡) of 77 kJ mol−1. The CI reaction with CH4, C2H6, NH3, and chlorinated ethanes is not energetically favored and has high barriers in the range of 253 to 362 kJ mol−1. The more probable reaction with SO2 forms a secondary ozonide (SOZ) intermediate with a barrier of 9 kJ mol−1, while the ΔG‡ to dissociation is 101 kJ mol−1. Among the reactions studied, the one with \( \dot{\mathrm{N}} \)O had the lowest ΔG‡ for its rate-determining step. The ΔG‡ values of the first step addition of O3, NH3, SO2, and \( \dot{\mathrm{N}} \)O do not exceed 84 kJ mol−1. In contrast to previous predictions, the \( \dot{\mathrm{N}} \)O reaction with the CI did not proceed through cyclic adduct formation. The findings agree with previous studies which found that CIs act as oxidizing agents, converting SO2 to SO3, and \( \dot{\mathrm{N}} \)O to \( \dot{\mathrm{N}} \)O2. Thus, the CIs of biogenic compounds should be added to the list of atmospheric oxidizing agents along with O3, NO3, and OH radicals.