Inside Back Cover: Origin of the α‐Effect in SN2 Reactions (Angew. Chem. Int. Ed. 38/2021)

The α-effect is a “reactivity booster” that affords the less basic peroxide (HOO−) the edge over hydroxide (HO−) in the Grand Prix of SN2 Reactivity. In their Research Article on page 20840, Trevor A. Hamlin and co-workers equip researchers with two criteria that α-nucleophiles need to fulfill to exhibit an α-effect: (i) a small HOMO lobe on the nucleophilic center, to reduce the destabilizing Pauli repulsion with the substrate; and (ii) a high-energy HOMO to overcome the loss of favorable orbital overlap with the substrate.