Definition of Distonic Ions

In the intermediate generated by the first a-cleavage of cyclohexyl compounds charge and radical are not located at the same atom as is the case with molecular ions, but at distant positions. The term distonic ion was derived from the Greek word for separate to describe such ionic species. [40] Distonic ions represent an ionic class of their own. [40-42] 

Definition A distonic ion is a positive radical ion, which would formally arise by ionization of a zwitterion or a diradical, by isomerization or fragmentation of a classical molecular ion, or by ion-molecule reactions. Consequently, distonic ions have charge and radical at separate atoms in a conventional valence bond description. [42,43] 

However, bearing charge and radical at separate sites is not a sufficient condition for an ion to be denoted distonic, e.g., the ethylene molecular ion may be written as such, but the corresponding neutral is not best represented as zwitterion and therefore the ethylene molecular ion by definition is not a distonic ion  

The expressions nonclassical and hypervalent ion have also been used by some authors to describe distonic ions, but these are incorrect and thus should no longer be used. The term ylidion is limited to species where charge and radical are at adjacent positions. Thus, to describe the distance between charge and radical site, the terms a- (1,2-) distonic ion, p- (1,3-) distonic ion, y- (1,4-) distonic ion, and so forth are now in use [42,43] 

---