A Computational Re-examination of the Criegee Intermediate–Sulfur Dioxide Reaction
| Autor: | Ke Huang, Matthew R. Hermes, Keith T. Kuwata, Emily J. Guinn, Jon M. Mathison, Jenna Fernandez |
|---|---|
| Rok vydání: | 2015 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry A. 119:10316-10335 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/acs.jpca.5b06565 |
| Popis: | The atmospheric oxidation of sulfur dioxide by the parent and dimethyl Criegee intermediates (CIs) may be an important source of sulfuric acid aerosol, which has a large impact on radiative forcing and therefore upon climate. A number of computational studies have considered how the CH2OOS(O)O heteroozonide (HOZ) adduct formed in the CI + SO2 reaction converts SO2 to SO3. In this work we use the CBS-QB3 quantum chemical method along with equation-of-motion spin-flip CCSD(dT) and MCG3 theories to reveal new details regarding the formation and decomposition of the endo and exo conformers of the HOZ. Although ∼75% of the parent CI + SO2 reaction is initiated by formation of the exo HOZ, hyperconjugation preferentially stabilizes many of the endo intermediates and transition structures by 1-5 kcal mol(-1). Our quantum chemical calculations, in conjunction with statistical rate theory models, predict a rate coefficient for the parent CI + SO2 reaction of 3.68 × 10(-11) cm(3) molecule(-1) s(-1), in good agreement with recent experimental measurements. RRKM/master equation simulations based on our quantum chemical data predict a prompt carbonyl + SO3 yield of >95% for the reaction of both the parent and dimethyl CI with SO2. The existence of concerted cycloreversion transition structures 10-15 kcal mol(-1) higher in energy than the HOZ accounts for most of the predicted SO3 formation. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|