Fig. 4. Value of including QM-calculated chemically meaningful descriptors is illustrated using an iodination reaction. Blue dots indicate the major and minor iodination sites. Numbers next to the major/minor site are the predicted score for the selectivity, using GNN or QM-GNN model. The GNN model predicts the wrong major product, assigning reaction to form 2 a lower score (0.35) than formation of the minor product (0.54). The QM-GNN model gives the correct selectivity. For each major/minor site, two most-similar reactions in the training set as judged by each model are given, with the red dot indicating the reacting site. For QM-GNN model, QM descriptors are given for the major/minor site in the order of atomic charge (1e–2 e), electrophilic Fukui index (1e–2 e), nucleophilic Fukui index (1e–2 e), and NMR shielding constant (ppm).