2022 Volume 37 Pages 32-48
Relative gas-phase stabilities (ΔEX) of ring-substituted 2-phenyladamantane-5,7-diyliums were computationally determined as the energy difference of hydride transfer equilibria between ring-substituted and their parent dications. Obtained substituent effect was compared to those of α,α-dimethylbenzyl cations (σ+-reference) and 90˚-fixed α,α-dimethylbenzyl cations (σ0-reference). Statistical analyses revealed negligible through-resonance effect and significantly large saturation effect operating in the dication. The result is in contrast with those of 1-phenylcyclobutane-1,3-diyliums and 1-phenylcyclopentane-1,3-diyliums which show both significant through-resonance and saturation effects and that of 2-phenyl-1,3-dehydroadamantane-5,7-diyliums which shows both small through-resonance and saturation effects. The through-resonance and saturation effects have been shown to be independent of each other to confirm that the three-term extended Yukawa-Tsuno equation, -ΔEX = ρ (σ0+r+ΔσR++s+Δσs+), is intrinsic in substituent-effect analyses for the dicationic systems.
