Application of Gassman-Fentiman tool of increasing electron demand to stable carbocations using nuclear magnetic resonance spectroscopy

Advances in Metal Chemistry of Quinonoid Compounds: New Types of Interactions between Metals and Aromatics

“…13 C NMR is routinely utilized as a powerful technique to probe the positive charge distribution in carbocations in general and in benzyl cations, in particular . It is expected that introducing electron-donating substituents into the position para to the methylene group should result in stabilization of ring-localized charge (i.e., methylene arenium form), while electron-withdrawing groups would result in the charge being localized more at the methylene group.…”

Long-lived cyclopropylcarbinyl cations

“…However, effects other than charge density also can affect chemical shifts. 80 When phenyl and cyclopropyl groups compete with each other intramolecularly for the positive charge, as in 182 and 183, indication on the stabilizing effect 182 183 should be revealed. However, it was found that the activation energy for the hydride migration in these cyclopropyl-substituted cations is much higher, thus effectively preventing their interconversions.78,79 Electrophilic addition reactions to olefins involve formation of carbocations and should give evidence complimentary to the solvolytic studies.…”

Studies on Long-Lived (Pentafluorosulfanyl)phenyl-Substituted Carbocations

“…The “Gassman–Fentiman tool of increasing electron demand” is one of the many methods available for the detailed study of carbocations. Although initially used in solvolytic studies by Gassman, our group and others have extended the methodology to the study of stable carbocations as well. The onset of n , π, and σ-participation can be detected by varying the nature of the groups attached to the aryl ring from electron-releasing to electron-withdrawing.…”