Theoretical insights into the cycloaddition reaction mechanism between ketenimine and methyleneimine: An alternative approach to the formation of pyrazole and imidazole

The cycloaddition reaction mechanism between interstellar molecules, ketenimine and methyleneimine, has been systematically investigated employing the second-order Moller-Plesset perturbation theory (MP2) method in order to better understand the reactivity of nitrogenous cumulene ketenimine with the C=N double bond compound methyleneimine. Geometry optimizations and vibrational analyses have been performed for the stationary points on the potential energy surfaces of the system. Calculations show that five-membered cyclic carbene intermediates could be produced through pericyclic reaction processes between ketenimine and methyleneimine. Through the subsequent hydrogen transfer processes, carbene intermediates can be isomerized to the pyrazole and imidazole compounds, respectively. The present study is helpful to understand the formation of prebiotic species in interstellar space.