Unimolecular Decomposition Reactions of Propylamine and Protonated Propylamine

A detailed computational study of the decomposition reaction mechanisms of cis-propylamine (cis-PA), trans-propylamine (trans-PA), and the cis-isomer of its protonated form (cis-HPA) has been carried out. Fourteen major pathways with their kinetic and thermodynamic parameters are reported. All reported reactions have been located with a concerted transition state, leading to significant products that agree with previous theoretical and experimental studies. Among six decomposition pathways of trans-PA, the formation of propene and NH₃ is the significant one, kinetically and thermodynamically, with an activation energy barrier of 281 kJ mol^-1. The production of two carbenes is found via two different transition states, where the reactions are thermodynamically controlled and reversible. Furthermore, five decomposition pathways of cis-PA have been considered where the formation of ethene, methylimine, and H₂ is the most plausible one with an activation energy barrier of 334 kJ mol^-1. The results show that the formation of propene and NH₄ ⁺ from the decomposition of cis-HPA is the most favorable reaction with an activation barrier of 184 kJ mol^-1, that is, the lowest activation energy calculated for all decomposition pathways.