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.