Distonic Stabilization of Cation-Radicals

According to mass spectrometric studies by Bigler and Hesse (1995), a,(i)-diaminoalkane cation-radicals undergo intramolecular hydrogen atom rearrangements leading to the formation of distonic cation-radicals  

The example of glycine is much more descriptive. The spin and charge separation has been found at the C- and the N terminus, respectively (Rodriguez-Santiago et al. 2000). 

The activation energy for this separation is 38 kJ mol in the ground state, with no barrier in the first excited state (Nielsen et al. 2000). The driving force is the high proton affinity of the amino group. This leads to the formation of such stabilized distonic cation-radicals. 

The onium form of the ethyl acetate cation-radical is more stable by 50 kJ moH than the corresponding carbonyl form (Rhodes 1988). The CHj fragment is stabilized by the three-electron bonding with the neighboring oxygen in the following manner -O.. CH2. Oxidation of the carbonyl 

For another example of the strong dnality in the chemical behavior of distonic cation-radicals, see Moraes and Eberlin (1998). In the gaseons phase, m- and /7-dehydrobenzoyl cation-radicals ( CgH4C =0) react selectively either as free radicals or as acylium ions, depending on the choice of the reacting partner. Transacetalization with 2-methyl-l,3-dioxolane, ketalization with 2-methoxy-ethanol and epoxide ring expansion with epichlorohydrin demonstrate their acylium reactivity. 

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