Unraveling the reaction mechanism on primary and secondary decomposition of iso-propylamine

Abstract

Iso-propylamine holds crucial significance as an intermediate in co-combustion processes and a favored amine donor, yet its comprehensive investigation remains limited. In this study, CCSD(T)/CBS//M06-2X-D3(0)/6–311++G(d,p) approach was employed to investigate the H-abstraction reactions of iso-propylamine, along with an analysis of subsequent primary and secondary decomposition reactions. Additionally, the kinetic data of all reactions on the potential energy surface was investigated via the transition state theory (TST), rigid-rotor-harmonic-oscillator (RRHO) model, and Eckart-effect tunneling correction. The results indicated that the H-abstraction reactions of NO₂ radicals with iso-propylamine were endothermic, whereas the H-abstraction reactions involving H/CH₃/NH₂ radicals with iso-propylamine were exothermic. The H-abstraction channels of $\beta$-site are most competitive at low temperatures, owing to its chemical energies of saddle points are relatively lower. The H-abstraction reactions of iso-propylamine are not affected by weak interactions which adhered to the Evans-Polanyi principle. Isomerization reactions predominantly occur at low temperatures due to their energetic favorability, while $\beta$-dissociation reactions become increasingly significant as the temperature increases. Consequently, $\beta$-dissociation emerges as the primary channels for the consumption of isopropyl radicals at the high temperatures. In the primary decomposition reactions, the scission of the C-N bond occurs readily. However, in the subsequent secondary decomposition stages, the scissions of C-N bond involve transition state which characterized by a higher-energy structure. This study extends the kinetic data on the primary and secondary decomposition of isopropyl radicals across a broad range of temperatures and pressures.