Pyrazine hyperfine splitting

A further significant consequence of variation in the extent of conjugation in aromatic radicals is demonstrated by a comparison of proton hyperfine splittings in pyrazine and quinoxaline anion-radicals (22,23) and also in the... 

Kochi and co-workers have prepared the anion-radical 231 of [l,2,5]thiadiazolo[3,4-c][l,2,5]thiadiaz.ole. Also prepared were the anion-radicals of [l,2,5]thiadiazolo[3,4-h]pyrazine (232) and [1,2,5]thiadi-azolo[3,4-fe]quinoxaline. Hyperfine splittings are indicated for 231 and 232 in gauss. The radicals were prepared by alkali-metal reduction in THF the observation of counterion splittings indicates their occurrence in ion-pairs. Radical 231 is of interest from the point of view of the nature of the... 

The results of analyses of the ESR spectra of various reaction systems are summarised in Table II. It was shown that all spectra have in common the splittings arising from two equivalent nitrogens (about 8.2 G) and four equivalent protons (about 3.0 G), and additionally from an even number of equivalent protons with different splitting constants. These assignments let to the reasonable assumption that the radical products are N,N -disubstituted pyrazine cation radical derivatives, as shown in Fig. 4. This assumption was strongly supported by the fact that the hyperfine structure as well as the g-value of the ESR... 

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