Remote charge site fragmentation anions

In cases of extensive branching, as for the alkylbenzenesulfonates, the CnH2n+2 1°33 series is significantly perturbed compared to the straight chain alkyl sulfates, but it is sufficiently abundant to show perturbations in the loss pattern. These perturbations may be interpretable for identifying branch points. N-Acylated amino acids also show a suppressed remote charge site loss series because the preferred fragmentations are the decarboxylation of the parent anion and formation of the carboxylate anion of the amino acid (8). 

The potassium salt of the 2,2 -dipyridyl acetylene anion-radical represents another important example. In this case, the spin and charge are localized in the framework of N-C-C=C-C-N fragment. The atomic charge on each nitrogen atom is -0.447, that is, close to unity in total. The energy of this ion pair is minimal when the potassium counterion is located midway between the two rather close nitrogen lone pairs. Such a structure is consistent with the fact that the ESR spectrum of this species is almost insensitive to temperature. It means that the counterion does not hop between two remote sites of the anion-radical (Choua et al. 1999). 

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