Intramolecular hydrogen migration in Alkylperoxy and Hydroperoxyalkylperoxy radicals: Accurate treatment of hindered rotors

Abstract

We have calculated the thermochemistry and rate coefficients for stable molecules and reactions in the title reaction families using CBS-QB3 and B3LYP/CBSB7 methods. The accurate treatment of hindered rotors for molecules having multi- ple internal rotors with potentials that are not independent of each other can be problematic and a simplified scheme is suggested to treat them. This is particu- larly important for hydroperoxyalkylperoxy radicals (HOOQOO). Two new ther- mochemical group values are suggested in this paper and with these values the group additivity method for calculation of enthalpy as implemented in RMG gives good agreement with CBS-QB3 predictions. The barrier heights follow the Evans- Polanyi relationship for each type of intramolecular hydrogen migration reaction studied.