Extracting and curating the initial data from the BH9 dataset BH9 is an extensive and diverse benchmark dataset for reaction and activation energies, composed of 449 chemical reactions belonging to nine types common in organic chemistry and biochemistry. The molecular species in BH9 comprise main-group elements (H, C, N, O, F, P, S, and Cl), plus B and Si. The pericyclic subset, on which we will focus throughout this study, consists of 140 Diels-Alder (DA), [3+2] cycloaddition (DC), electrocyclic, [3,3] rearrangement (RR), [6+4], [4+6], [8+2] and [2+2+2] cycloaddition reactions. We focus on this specific reaction class because of its chemical and biological importance, as well as the good understanding and relative robustness of the corresponding mechanisms.