Radical anions and nitroxides from alkylthio-, alkylsulphinyl-, and alkylsulphonyl-nitrobenzenes

The e.s.r. spectra of the radical anions and nitroxides from nitrobenzenes substituted with SR, SOR, and SO2R groups are reported. The effect of the substituent on the spin density distribution as revealed by the variations of the nitrogen and ring protons splitting constants, is discussed. While the alkylsulphinyl and alkyisulphonyl groups behave as electron attractors, their electron-withdrawing ability being little dependent on the nature of the alkyl substituent, the alkylthio-group has an electron-acceptor character strongly dependent on the dimensions and therefore on the conformation of the aliphatic substituent. As a possible explanation it is suggested that ?-? conjugation with electron release from the ? orbital containing the unpaired electron to the low lying ?* antibonding orbital of the C-S bond is responsible for this behaviour.