and the full dataset of radical and anionic reactivity. All relative reaction rates estimated at 298 K. From the reported reaction conditions, ∆∆G ‡ can be roughly estimated as 5 kcal mol -1 (see Section S6 for further discussion), which is only a 1 kcal mol -1 difference from the rule of thumb prediction. In short, the enhanced reactivity of bicyclo[1.1.0]butane can therefore be predicted simply by looking up strain release energies and counting the number of three-membered rings.