ABSTRACT
The oxidation is occasionally so easy that it may be difficult to isolate a hydroxylamine without a corresponding radical impurity. The stability of nitroxyl group against oxidizers increases with the number of units in heterocycle, for bicyclic compounds with bridge hydroxylamino group, and for compounds with higher electron-accepting characters of their substituents. The nitroxyl group may be generated by the one-electron reduction of the oxammonium group. The nitroxyl group is very easily reduced to the hydroxylamino group by iodides in acid media. The analysis of the data on the generation of nitroxides shows amines and hydroxylamines to be synthetically the most useful precursors of nitroxides. The hydroxylamine-nitroxide equilibrium has been studied using hydroxylamino derivatives, containing N isotope to create the relative oxidative ability scale of cyclic nitroxides and study structural effects on the oxidative ability of the nitroxyl group. The introduction of electron-accepting substituents lowering the basicity both of the nitroxyl group and the hydroxylamine formed hinders the disproportionation reaction.
