Revealing new pathways for the reaction of Criegee intermediate CH2OO with SO2

Abstract

Criegee intermediates play an important role in the tropospheric oxidation models through their reactions with atmospheric trace chemicals. We develop a global full-dimensional potential energy surface for the CH2OO + SO2 system and reveal how the reaction happens step by step by quasi-classical trajectory simulations. A new pathway forming the main products (CH2O + SO3) and a new product channel (CO2 + H2 + SO2) are predicted in our simulations. The new pathway appears at collision energies greater than 10 kcal/mol whose behavior demonstrates a typical barrier-controlled reaction. This threshold is also consistent with the ab initio transition state barrier height. For the minor products, a loose complex OCH2O ∙ ∙ ∙ SO2 is formed first, and then in most cases it soon turns into HCOOH + SO2, in a few cases it decomposes into CO2 + H2 + SO2 which is a new product channel, and rarely it remains as ∙OCH2O ∙ + SO2. Criegee intermediates such as CH2OO play an important role in tropospheric oxidation models through their reactions with atmospheric trace chemicals. Here, the authors develop a global full-dimensional potential energy surface for the CH2OO + SO2 system, reveal how the reaction happens step by step using quasi-classical trajectory simulations, to show a new direct stripping pathway forming the main products CH2O and SO3 and a new product channel.