A quantum chemical and kinetics study on the unimolecular reactions of fuel radicals formed during the oxidation of n‐propylamine.

The major intermediate product under co‐combustion conditions of hydrocarbon fuels with ammonia are amines. Herein, we have theoretically investigated the unimolecular reactions of fuel radicals formed during the oxidation of n‐propylamine. Quantum chemical calculations were performed to obtain the optimized structures and vibrational frequencies of reactants, products, and transition states at the B3LYP/aug‐cc‐pVTZ theory level. CCSD(T) single point energy calculations with the basis sets of aug‐cc‐pVDZ and aug‐cc‐pVTZ were further performed against the optimized structures, and the energies were extrapolated into infinite basis limit. Pressure‐dependent rate constants were calculated using Rice–Ramsperger–Kassel–Marcus/master equation analysis. The major reaction pathways for the fuel radicals were found to be β‐scission reactions at CC or CN bonds, and minor pathways were internal hydrogen shift and β‐scission reactions at CH or NH bonds. The calculated reaction rate constant trends were attributed to the decrease in CC and CN bond dissociation energies due to substitution effects from the amino group. [ABSTRACT FROM AUTHOR]