Isomerization and decomposition of a Criegee intermediate in the ozonolysis of alkenes: dynamics using a multireference potential.
The isomerization and decomposition dynamics of the simplest Criegee intermediate CH2 OO have been studied by classical trajectory simulations using the multireference ab initio MR-PT2 potential on the fly. A new, accelerated algorithm for dynamics with MR-PT2 was used. For an initial temperature of 300 K, starting from the transition state from CH2 OO→CH2 O2  , the system reaches the dioxirane structure in around 50 fs, then isomerizes to formic acid (in ca. 2800 fs), and decomposes into CO+H2 O at around 2900 fs. The contributions of different configurations to the multiconfigurational total electronic wave function vary dramatically along the trajectory, with diradical contributions being important for transition states corresponding to H-atom transfers, while being only moderately significant for CH2 OO. The implications for reactions of Criegee intermediates are discussed.
Department of Chemistry, University of Helsinki, A.I. Virtasen aukio 1 (P.O. BOX 55), 00014 Helsinki (Finland). jaroslaw.kalinowski@helsinki.fi.
Jaroslaw
J
Kalinowski
Markku
M
Räsänen
Petri
P
Heinonen
Ilkka
I
Kilpeläinen
R Benny
RB
Gerber
Criegee intermediates; ab initio calculations; molecular dynamics; ozonolysis; transition states