LAUSR

Abstract We used the double-hybrid DFT functional B2PLYP and the MP2 approximation to determine the roles of the Criegee and DeMore mechanisms in the first step of the ozonolysis of trans-isoprene. We confirmed the predicted structures of the transition states and the activation energies. We used B2PLYP with the aug-cc-pVDZ basis set to perform the full geometry optimization of stationary points for the rate-determining steps of both mechanisms. We calculated rate constants for both reaction mechanisms for each trans-isoprene double bond and the whole molecule under standard conditions. We demonstrated that double bonds of trans-isoprene have different dominant ozonolysis mechanisms. In the bond surrounded by one carbon and three hydrogen atoms, 83% of ozonolysis goes through Criegee, while in the bond surrounded by two carbon and two hydrogen atoms 75% of ozonolysis goes through DeMore. The calculated rate constant of the first step of trans-isoprene ozonolysis is 1920 l · mol - 1 · s - 1 at 298.15 K. 46% of the ozonolysis reaction goes through Criegee and 54% through DeMore.