H-abstraction reactions of pentacyclic carbonates: a computational kinetic study

Theoretical studies of H-abstraction reactions were conducted for typical solvents in the battery industry, such as ethylene carbonate (EC), propylene carbonate (PC), 2,3-butylene carbonate (23BC), and 1,2-butylene carbonate (12BC), to aid in the future development of chemical kinetic models for the pyrolysis and combustion of pentacyclic carbonates. Using the M06-2X/6-311+G(d,p) method with the automation program, the geometries, vibrational frequencies, and zero-point energies of the stationary points were calculated. The single-point energy calculations were then refined at the CCSD(T)-F12/cc-pVTZ-F12 level of theory. The rate coefficients were calculated using transition state theory (TST) with one-dimensional hindered rotor and Eckart tunneling corrections. Comparative analyses of the rate coefficients for H-abstraction channels were conducted at various sites to determine the primary pathways in EC, PC, 23BC, and 12BC. Furthermore, the rate coefficients of H-abstraction at tertiary, secondary, and primary carbon sites were compared across these cyclic carbonates. It was found that the same sites showed similar rate coefficients, which can be used as a reference in similar cases where the rate constant is not available. The rate coefficients were further incorporated into detailed kinetic models. The updated models reasonably predict ignition delay times, laminar flame speeds, and pyrolysis data from the literature. Overall, this study offers useful insights for the follow-up model development of cyclic carbonates.