OH Roaming as a Key Pathway in the Anti-CH₃CHOO + H₂O Reaction Yielding CH₃COOH and H₂O

The reaction of anti-CH₃CHOO with H₂O is a crucial atmospheric process, resulting in the end products CH₃COOH + H₂O through the dissociation of the intermediate hydroxyethyl hydroperoxide (CH₃CH(HO)OOH, HEHP). Based on an accurate full-dimensional PES, we have obtained detailed dynamics information for this reaction through quasi-classical trajectory simulations. We report two reaction mechanisms for the CH₃COOH + H₂O product channel: one involving a direct mechanism through the transition state and the other an intriguing OH roaming mechanism. The roaming pathway proceeds via the dissociation of HEHP into OH and the hydroxyethoxy radical (CH₃CH(HO)O, HEO), where the OH radical roams near HEO and abstracts a hydrogen atom, subsequently forming H₂O and CH₃COOH. The presence of this roaming pathway significantly increases the yield of CH₃COOH + H₂O. This work provides new dynamical support for the study of the anti-CH₃CHOO + H₂O reaction and enriches our understanding of atmospheric chemistry.