Because bond dissociation energy calculation necessitates the treatment of radical species (see Figure ), both closed-shell molecules and derived radicals needed to be included in the training and testing datasets. In this work, we have focused on aliphatic C-H bond dissociation energies and, as a result, only radicals generated by a homolytic cleavage of a sp 3 C-H bond were considered. To generate the training set, from the "drug-like" subset of the ZINC database we have randomly selected just under 13, 000 SMILES strings that contained only carbon, hydrogen and oxygen chemical elements (see Table ). From these SMILES strings, 3D conformers of closed-shell molecules were generated by RDKit. A number of open-shell radical structures, corresponding to the number of sp 3 hydrogen atoms in the parent closed-shell molecule, were generated for each of the closed-shell molecules by in turn removing (deleting) the appropriate hydrogen atom. From this pool of open-and closed-shell structures, nearly 17, 000 were selected as the starting geometries for the molecular dynamics (MD) simulations.