Abstract
ESR spectra of free radicals from 23 derivatives of 1,4-benzoquinone imines, obtained by electrochemical or chemical reduction of these compounds or by oxidation of the corresponding p- aminophenols, have been studied in solution. In the course of the processes mentioned, anion radicals of 1,4-benzoquinone imines are formed while in the case of reduction of N-sulphonyl derivatives (depending on the potential of electrochemical generation) neutral radicals can be obtained as well. Anion radicals of the corresponding 1,4-benzoquinones are formed in the case of N-arylbenzoquinone imines; they can also be obtained in other cases if the water content in the solution is high enough (apparently as a result of hydrolysis). The pathways of free radical for- mation and their structural peculiarities are discussed. Neutral free radicals of 1,4-benzoquinone sulphonyldiimines are stable enough to be isolated in the solid phase. The latter are assumed to be of quinoid structure with protonated imine nitrogen.
Published Version
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