Both substituted cations (Ama + and Ada-CN + ) demonstrated a relatively low yield of ultrafast H loss happening within 1 ps of simulations (≲3 %), which is comparable to the case of Ada + (<8 %). In addition, only one trajectory for Ama + showed NH 2 loss and no other fragments were found for both cations within 1 ps. Remarkably, for Ama + , majority of the parent ion trajectories (∼87 %) evinced intramolecular rearrangement (cage opening) in agreement with low energy barriers reported by George and Dopfer . In contrast to Ama + , rearrangement percentage was found to be much lower for Ada-CN + (≲6 %), which is similar to that for Ada + (≲7 %).