Carbon Acidity. 66. Equilibrium Ion Pair Acidities of Substituted Diphenylmethanes in Cyclohexylamine

Article abstract of DOI:10.1021/ja00310a037

The pK_CsCHA values are reported for a number of symmetrically meta- and para-substituted diphenylmethanes.The pK_CsCHA values for the meta series (Me, 33.8; OMe, 32.7; F, 29.9; CF3, 28.9; Ph, 32.3; H, 33.4) give a normal Hammett plot with ρ = 9.69.The para series (Me, 35.1; OMe,37.6; Ph, 30.8; NMe2, 38.6; SPh, 28.8; CN, 23.0; SO2Me, 22.4) do not fit attempted correlations with ?, the Yukawa-Tsuno modifications, or dual substituent parameter approaches.Electron-donating groups are more anion destabilizing than in other reference systems. "Amphoteric" substituents, those that stabilize both anions and cations (phenyl, thio, etc.), cause special problems in generalized correlations.