Two Pathways for Dissociation of Highly Energized syn-CH3CHOO to OH Plus Vinoxy.

Ozonolysis of alkenes is an important nonphotolytic source of hydroxl radicals in the troposphere. The reaction proceeds through cycloaddition and subsequent decomposition to a carbonyl oxide, known as Criegee intermediates. Ozonolysis of alkene releases about 50 kcal/mol excess energy to form highly energized Criegee molecules, which can be stabilized and undergo further reaction or dissociate to OH+vinoxy products. The dissociation dynamics of partially stabilized Criegee (syn-CH3CHOO) has been thoroughly studied recently, in which the molecules dissociate by first isomerizing to vinyl hydroperoxide (VHP). Here we examine the dissociation dynamics of highly energized syn-CH3CHOO (42 kcal/mol), and a second, prompt dissociation path is discovered. The dissociation dynamics of these two paths are carefully examined through the animation of trajectories and the energy distributions of products. The new prompt path reveals a distinctly different translational energy and internal energy distributions of products compared to the known path through VHP.