Theoretical and experimental studies of the dissociation dynamics of methaniminium cation, CH2NH2+→CHNH++H2: Reaction path bifurcation

Abstract

The unimolecular dissociation of CH2NH2+ has been investigated experimentally and theoretically. Kinetic energy release distribution was obtained by analyzing the mass-analyzed ion kinetic energy profile. Critical configurations along the reaction path were investigated by electronic structure calculations at the HF, MP2, QCISD, and B3LYP levels using the 6-31G** and 6-311+G** basis sets. Reaction path bifurcation was observed at all the levels. The bifurcation point was in the entrance region (before the transition state) at the HF level. This point moved to the exit region when the electron correlation effect was included at the MP2, QCISD, and B3LYP levels. A global potential energy surface incorporating this bifurcation feature was constructed by interpolation at the MP2/6-311+G** level. Classical trajectories were calculated on this surface and product mode-specific energies were evaluated. Based on these data, various experimental observations, lack of hydrogen scrambling in particular, could be adequately explained.