The most prominent change in the nature of the substrate-bound I 2 catalyst was observed within Int1, as evidenced by variations in the bond length, ρ BCP , and the H value (Table ). These findings indicate a change from covalent to non-covalent characteristics in the I 2 catalyst while activating the trans-crotonophenone substrate. Furthermore, in addition to the aforementioned data that elucidate the nature of the I 2 catalyst, the same investigation was conducted to examine the nature of the interaction between I 2 and the α-carbon of the trans-crotonophenone substrate, comparing it to the geometrically optimised C-I bond in the isopropyl iodide control molecule. Similar to the I 2 catalyst, the most notable and significant transition in nature was observed within Int1 of the reaction pathway (Table ).