Space Structure and Skeletal Isomerization of Ion-Radicals

As to the cation-radical version of this isomerization, there are testimonies on the transition of the norcaradiene carcass into the cycloheptatriene skeleton. Calculations at the B3LYP level shows that cycloheptatriene cation-radical is more stable than norcaradiene cation-radical by ca. 29 kJ mol (Norberg et al. 2006). Hydrocarbon ion-radicals with strained ring structures have a tendency to undergo facile rearrangement to enforce the unpaired electron delocalization and release their strain energy. 

Adam et al. (2003) also explained their experimental results on the rearrangement of housanes through mechanisms that include the formation of distonic cation-radicals in the intermediary step. Their mechanisms were grounded by kinetic analysis (Trofimov 2004). 

The stereochemical opportunities of the ion-radical reactions deserve further study because of their importance in science and commercial applications. Although this branch of ion-radical organic chemistry is at present insufficiently developed, further development seems to be inevitable. 

Macias-Ruvalcaba, N.A. Evans, D.H. (2006a) Langmuir 22, 10683. 

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