2023 Volume 38 Pages 53-63
Relative gas-phase stabilities (Total Stabilization Energy, TSE) of Meisenheimer complexes generated by addition of hydride anion to 4- or/and 5-substituted 2-nitrobenzenes carrying various functional groups (Y) at position 1 were computationally determined utilizing hydride transfer reactions with parent 1-′Y′-2-nitrobenzene at the B3LYP/6-311+G(2d,p) level of theory. As for the Y, electronically various groups were introduced. Nine sets of substituent effects obtained were compared with that of benzoate anions that are used as the σ0-reference system. It has become apparent that the gas-phase stabilities of these Meisenheimer complexes are governed by three kinds of electronic effects of the basic, through-resonance, and saturation effects and all of the substituent effects are excellently correlated by the three-term extended Yukawa-Tsuno equation: 
. Anion Stabilization Energies (ASE) of these Meisenheimer complexes were also calculated utilizing Y– transfer reactions in a similar manner, and the substituent effects obtained are also found to be accurately correlated by the extended Yukawa-Tsuno equation. The r – values on TSE are found to be very similar to those on ASE, and did not show significant dispersion by the change of the Y. On the other hand, the s values on TSE showed significant variation, although those on ASE distributed in a narrow range. This shows that the s value depends not only on the anion but also on the nature of neutral species. These results revealed a wide applicability of the extended Yukawa-Tsuno equation not only to the anions of benzene derivatives but also to non-aromatic anions.
