Solvation-induced line-width alternation in the electron spin resonance spectra of the meta-dinitrobenzene anion and of various symmetrically substituted dinitro-compounds in the benzene and naphthalene series

Abstract

The e.s.r. spectra of a wide range of symmetrical radical anions of dinitrobenzene and dinitronapthalene in dimethyl-formamide–ethanol and ethanol–water are reported. Line-width alternation, which increased markedly with addition of ethanol to dimethylformamide solutions, is attributed to asymmetric solvation. Structural factors governing the rates of equilibration are discussed. N-Alkyl-2,6-dinitroaniline anions were abnormal in that asymmetry was relatively long lived even in dimethylformamide at room temperature. This is attributed to internal hydrogen-bonding between the anion proton and an oxygen atom of one nitro-group. Hydroxylamine has proved to be a useful reagent for the reduction of aromatic dinitro-compounds to their radical anions without spectral contamination by more highly reduced substances.