Computational study for the second-stage cracking of the pyrolysis of ethylamine: Decomposition of methanimine, ethenamine, and ethanimine

The mechanism that accounts for the observed experimental activation energy for the decomposition of ethylamine (EA) is still unknown. This paper reports the first detailed study of possible mechanisms for the pyrolysis of second-stage cracking product of ethylamine: the decomposition reaction of methanimine, ethanimine, and aminoethylene. Investigated reactions characterize either H₂ elimination or 1,3-proton shift. These pathways result in the removal of H₂, CH₄, and NH₃; and the formation of hydrogen cyanide, acetylene, acetonitrile, ethynamine, and ketenimine. The IRC analysis was carried out for all transition state structures to obtain the complete reaction pathways. The stationary points were fully optimized at B3LYP and MP2 levels of theory using the 6-31G(d), 6-31G(2df,p), and 6-31++G(3df,3dp) basis sets. Based on comparing energetic requirements, we find 1,3-proton shift is the most probable pathway for the decomposition of ethanimine. The decomposition reaction of ethenamine was the most plausible reaction with an activation energy of 297 kJ mol^-1 calculated at the composite method of G4MP2.