Electrophilicities of Symmetrically Substituted 1,3-Diarylallyl Cations

Kinetics of the reactions of nine symmetrically substituted 1,3-diarylallyl cations with different nucleophiles were studied photometrically in dichloromethane, acetonitrile, and DMSO solutions. The second-order rate constants k2 were found to follow the correlation log k2 = sN(N + E). The electrophilicity parameters E of the title cations were derived, using the known values of sN and N of the nucleophilic reaction partners, and compared with the electrophilicities of analogously substituted benzhydrylium ions. Good linear correlations were found between the electrophilicities E and the quantum chemically calculated gas-phase methyl anion affinities of the allyl cations and the σ+ constants of the substituents X.