Abstract In the present work we have investigated the gas phase reactivity of protonated urea after collision with the diatomic inert gas N 2 , by studying the energy transfer and fragmentation induced by collisions. We first developed an analytical pair potential to describe the interaction between the projectile and the ion, and then performed QM/MM direct chemical dynamics simulations of the collision between the projectile and protonated urea in its two most stable isomers. In particular, the effect of the diatomic projectile, and the role of its initial rotational state, were compared with the fragmentation and energy transfer obtained previously ( J. Phys. Chem. A 2009, 113 , 13853) for the monoatomic projectile Ar. The diatomic projectile was found to be less efficient in energy transfer compared to the monoatomic projectile. In addition, rotational activation of UreaH + is dependent on the initial rotational quantum number of N 2 . Finally, we investigated the UreaH + gas phase reactivity as a function of its rovibrational activation by means of chemical dynamics simulations where the initial structure for the simulations is the transition state (TS) that the system can reach after collisional activation of the most stable isomer. The simulation time-length is not able to directly access this TS from the most stable isomer since its lifetime is notably longer, of about two order of magnitude in time.