Master equation simulations of the unimolecular reaction
dynamics
of the Criegee intermediate methacrolein oxide (MACR oxide) have been
performed under a variety of temperature and pressure conditions.
These simulations provide insight into how the unimolecular kinetics
vary across temperatures spanning the range 288–320 K. This
work has incorporated a new potential energy surface and includes
the anti-to-syn and cis-to-trans conformational dynamics of MACR oxide,
as well as the unimolecular reactions to form dioxirane and dioxole
species. The competition between the unimolecular reactivity of MACR
oxide and previously documented bimolecular reactivity of MACR oxide
with water vapor is explored, focusing on how this competition is
affected by changes in atmospheric conditions. The impact on the role
of MACR oxide as an atmospheric oxidant of SO2is noted.