Molecules with this property bind preferentially to ligands with even hapticity according to the Davies–Green–Mingos rules. An increase in this property due to lone pairs on atoms adjacent to a functional group of interest is described by the alpha effect. A reaction between an arene and a molecule with this property produces a reactive intermediate called the Meisenheimer complex. Solvents with this property react with their solutes in solvolysis reactions. A leaving group is kicked off an aromatic ring by a molecule with this property in the SNAr (“S-N-A-R”) mechanism. Inversion of chiral symmetry (10[1])occurs after a “backside attack” from a molecule with this property in SN2 reactions. For 10 points, name this property of molecules that can donate an electron pair to an electrophile. ■END■ (10[1])