Abstract Autoreduction of 2, 2, 6, 6-tetramethyl-1, 4-dioxopiperidinium ion to nitroxyl radical in alkaline medium involves a number of parallel and consecutive reactions. The primary products of the reaction of 2, 2, 6, 6-tetramethyl-1, 4-dioxopiperidinium with hydroxide ion are three nitroso compounds and N-hydroxy-2, 2, 6, 6-tetramethylpiperidine N-oxide. Isomerization of the nitroso compounds and elimination of acetone from the N-oxide give ...