Hyperconjugation in the electron resonance spectra of free radicals
Abstract
The electron resonance hyperfine splitting aH produced by protons of a methyl group attached to one of the aromatic carbon atoms of a π-electron radical is calculated by the valence bond theory, treating the exchange inter-action between the odd electron and the methyl group as a perturbation. The formula aH = Qρ which relates aH for a ring proton with the spin density ρ on the aromatic carbon atom also holds for methyl protons. Q is predicted to be positive with a theoretical value of about 28 gauss in the ethyl radical. Experimental data for several radicals indicate that Q is about 25 gauss. It is suggested that the CH3 and CH2 protons appear to be equivalent in the spectrunl of the ethyl radical because Q has the same magnitude for both. The spectra of some Wurster's blue ions are interpreted on the assumption that hyperconjugation takes place between methyl groups and the nitrogen atoms.
- Publication:
-
Molecular Physics
- Pub Date:
- 1958
- DOI:
- 10.1080/00268975800100291
- Bibcode:
- 1958MolPh...1..233M