The mappings generated by the existing tools-MAPPET, ReactionMap, and Marvinare less accurate than those generated by our algorithm. For example, in Figure , for reaction case 231, our algorithm with filter1 generated a unique correct mapping, while ReactionMap and Marvin produced incorrect mappings. Especially, an unusual phenol ring decomposition was observed in the mapping generated by Re-actionMap. These incorrect mappings involved three or four bonds cleavages, whereas the correct mapping involved only two bond cleavages. This case suggests that accurately calculating MCES (i.e., exactly minimizing the number of bonds broken and formed) is crucial for finding the correct mapping. As another example, in case 86, both ReactionMap and Marvin produced the same incorrect mapping. The assignment of oxygen atom's origin in this mapping was incorrect. Our algorithm, both with and without filtering, generated two plausible mappings, including both the incorrect and correct mappings. This case shows the difficulty of determining the correct mapping by calculating only one MCES and emphasizes the importance of our enumerative approach.