Distonic

I ShPh- shossing the slightly distoned square-pyramidal strueture It —yf)" lor the slightly more regular square-pyramidal BiPh>... 

Recent results of Bentrude et al. [44] suggest that a vinyl radical cation is first generated, and that the 1,3-distonic radical cation is reduced to a diradical involving a phosphoranyl radical moiety. However, because the phosphite and styryl moieties of phenylallylphosphites exhibit very close oxidation potentials [45], the presence of a phosphoniumyl radical cannot be totally ruled out. 

It can be assumed that in the domino process of, for example 5-3, a reactive radical cation intermediate 5-5 is initially formed [5]. The intramolecular cyclization then proceeds almost exclusively through a stable, chair-like, six-membered transition state 5-8 to give a distonic radical cation 5-9, which is trapped by the aromatic... 

The radical cations of urazole-annelated azoalkanes 65 were generated by pulse radiolysis and the transients characterized spectrally and kinetically by time-resolved optical monitoring. The initial distonic 1,3 radical cations 66 were detected, and the methyl-substituted 66 further deprotonates to radical 67 (Scheme 1) <1997JA10673>. 

TABLE 1. Energetic data for ionized amines and their distonic isomers 3... 

The sequential removal of H and H+ from isobutene-type structural units (so-called H2+ abstraction ) was also used to generate the radical anion of non-Kekule benzene , i.e. l,3-dimethylenecyclobutane-l,3-diyl (39) (Scheme 11). As shown by Hill and Squires161, this highly unusual, distonic C(,II(, isomer can be produced in pure form by reaction of O with 1,3-dimethylenecyclobutane (38). Working in a flowing afterglow mass spectrometer, subsequent reactions were again used to characterize this radical anion and differentiate it from other ( VdL, isomers. 

Intra-complex TMS+ abstraction by F yields the trimethylenemethane radical anion 33. Similarly, a number of other (mostly aromatic) distonic radical anions have been generated. Using the same approach, several other highly unsaturated distonic negative ions, such as the benzyne radical anions, were also studied164. 

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]... 

Cleavage of a bond without immediate dissociation of the precursor radical ion is one way for the generating distonic ions. Isomerization of molecular ions by hydrogen radical shift frequently leads to distonic ions prior to fragmentation and. 

Fig. 6.13. Activation energies for isomerization of primary amine molecular ions to distonic isomers with the heats of formation of the precursor M ions normahzed to zero. [46]...

Although amine-derived distonic ions have been mainly presented up to here, the occurrence of distonic ions is by far not restricted to this compound class. Instead, distonic ions are of high relevance as these ions play an important role as the cen-... 

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