Comprehensive Oxidation Mechanism of n-Butylamine and 2-Butylamine by H and OH Radicals: Insights into Reactivity

This study presents the accurate thermal rate constants for a series of hydrogen abstraction reactions involving 1- and 2-butylamine and key radicals H and OH. The potential energy surface resulting from these reactions was examined by using the M08-HX/ma-TZVP level of theory. The rate coefficients were calculated within the multistructural canonical variational theory with small-curvature tunneling correction (MS-CVT/SCT). Multistructural effects and the torsional anharmonicity corrections were evaluated through the rovibrational partition function calculated with the multistructural method based on a coupled torsional potential (MS-T). Our results demonstrated an influence of the position of the amino functional group on the kinetics. The gradual decrease in barrier heights was observed with increasing distance between the amino functional group and the reaction site. The calculated branching ratios demonstrated that the H-abstraction by the H radicals at the α-site is favored. In reactions involving OH radicals, the channel at the N-site shows a greater proportion due to its increased multistructural torsional anharmonicity and a reduced variational effect of other sites.