Anharmonic Effect of N-Propyl Peroxy Dissociation

Abstract

The anharmonic and harmonic dissociation rate constants of alkylperoxy (RO2) in different pathways, as well as those for the reactions of the n-propyl peroxy radical, were calculated using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. When the temperature/total energy increased, the rate constants of the different pathways varied independently, causing changes in the dominating/leading products. Anharmonic rate constants were larger than harmonic rate constants, and their difference increased with increasing temperature/energy. Therefore, the anharmonic effect cannot be neglected. The rate-determining steps of CH3CH2CH2OO dissociation are discussed. Then the anharmonic effect was found clearly for CH3CH2CH2OO dissociation, especially for the hydroperoxyalkyl radical (QOOH) dissociation. At low temperature, the rate constants were similar to those found from experiment, which indicated the RRKM theory was suitable for calculating the dissociation rates of RO2 species.