中央研究院 原子與分子科學研究所

Criegee intermediates (CIs), R₁R₂COO, are active molecules produced in the atmosphere from the ozonolysis of alkenes. Here, we systematically evaluated the reactivity of ten CIs with carbon monoxide and carbon dioxide using CCSD(T)-F12/cc-pVTZ-F12//B3LYP/6-311+G(2d,2p) energies and transition state theory. Many previous studies focused on alkyl substitution, but here we evaluated both alkyl and vinyl substitution toward the reactivity by studying five anti-type CIs: CH₂OO, anti-CH₃CHOO, anti-cis-C₂H₅CHOO, anti-trans-MACRO, anti-cis-MACRO; and five syn-type CIs: syn-CH₃CHOO, (CH₃)₂COO, syn-trans-C₂H₅CHOO, syn-trans-MVKO, and syn-cis-MVKO. Our study showed that reactions involving CO₂ have a large substituent dependence varying nearly five orders of magnitude, while those involving CO have a much smaller two orders of magnitude difference. Analysis based on the strain interaction model showed that deformation of the CI is an important feature in determining the reactivity with CO₂. On the other hand, we used the OO and CO bond ratios to analyze the zwitterionic character of the CIs. We found that vinyl substitution with π-conjugation results in smaller zwitterionic character and lower reactivity with CO. Lastly, the reactivity of CIs with CO as well as CO₂ were found to be not fast enough to be important in an atmospheric context.