Electron spin resonance studies. Part XXVI. Oxidative dimerisation of nitroalkane anions with the titanium(III)–persulphate system

Abstract

The oxidation of a nitroalkane R1R2CH·NO2 in basic solution by the titanium(III)–persulphate system gives the radical anion O2N·CR1R2·CR1R2·NO2[graphic omitted]. Evidence is adduced that oxidation occurs by reaction of the nitroalkane aci-anion with the sulphate radical anion to give the radical ·CR1R2·NO2, either by formation of an adduct followed by loss of sulphate ion or by electron transfer through a looser association of the reactants; the radical then reacts with a further aci-anion.E.s.r. observations show that the interconversion of, e.g. the radical anions O2N·CHMe·CH2·NO2[graphic omitted] and O2N·CH2·CHMe·NO2[graphic omitted] is rapid relative to the time scale of the flow experiments employed for their observation (ca. 100 sec.–1) but slow by comparison with particular differences between the hyperfine splitting constants of the radicals (ca. 107 sec.–1). The spectra of some of the radicals, and also those of related species in which one nitro-group is replaced by a hydroxy-group, reveal preferences for particular conformations.