Autoxidation of hydroxylamine in alkaline solutions

The autoxidation of hydroxylamine in aqueous alkali is shown to proceed by attack of oxygen on a deprotonated species yielding nitroxyl ion which can be oxidised further to peroxonitrite. In the presence of a metal sequestering agent (edta) the peroxonitrite ion is stabilised, although isomerising slowly to nitrate. A little nitrite is also formed. Decrease in pH leads to increasing production of gaseous products. In the presence of catalytic metal ions, nitrite is the main product, the hydroxylamine being largely consumed via reaction with peroxonitrite. Increasing concentration of copper(II) ions resulted in increasing production of nitrous oxide. A mechanism is presented for oxygen attack on hydroxylamine and a number of other autoxidation studies on N- and O-substituted hydroxylamines discussed.