Fig. 8

Heuristic approach to completing calculated mappings. The colored circles indicate which atoms can be heuristically mapped to each other. If the mapping calculation fails to determine a full mapping, the failures can be categorized in 3 classes. The first possibility is that no atoms have been mapped; no heuristic completion is possible here. In the second, two atoms of the same element are not mapped. In case of symmetry of the reactant or product, only one possible mapping remains: red on red and green on green. All other failures are categorized into the third class, for which no completion is possible