More specifically, in HAT reactions, the promotion energies, G r and G p , are proportional to the vertical/frozen bond dissociation energy (BDE) -or, more accurately, the bond dissociation free energy (BDFE) -of the covalent bond being broken in the reactant and product geometries respectively. The thermodynamic driving force, ∆E rp , in its turn corresponds to the (relaxed) BD(F)E by definition. f and B have been demonstrated to be fairly constant within narrow reaction families, e.g., when considering a carbonbased radical abstracting H atoms from a C-sp 3 bond. Since our ambition here is to generalize across the full space of (neutral) C, H, N, O containing organic radical reactions, this assumption can be expected not to hold perfectly. It has been demonstrated however that both of these parameters are connected to a variety of descriptors that can in fact be quantified straightforwardly.