Reaction Pathways, Thermodynamics, and Kinetics of Cyclopentanone Oxidation Intermediates: A Theoretical Approach.

Despite the promising role of cyclopentanone as a bioderived fuel, thermodynamic and kinetic data are lacking for low temperature oxidation regimes. In this study, ab initio calculations at the CBS-QB3 level explore the subsequent reactivity that results from O2-addition to 2- and 3-oxo cyclopentyl radicals, including expected reaction classes such as intra-H migration, HO2-elimination, cyclic ether formation, and β-scission along with their thermodynamic parameters. Some of the rates are similar to the analogous reactions of cyclopentane, but some other reactions of cyclopentanone are very different. The carbonyl group hinders H-migration from the α' position but promotes HO2-elimination. Enol peroxy formation from some hydroperoxy alkyl radicals of cyclopentanone is unexpectedly important, and so is HO2-elimination by β-scission. Our calculations also indicated that at engine relevant conditions the α-RO2 prefers to go back to the reactants 2-oxo cyclopentyl radical and O2. Therefore, the reactions resulting from HO2-addition to 2-oxo cyclopentyl are also provided. The lowest barrier channel identified on the singlet surface corresponds to an unexpected intra OH-migration path concerted with ring opening. This valuable information will advance the construction of improved kinetic models for the oxidation of cylopentanone.