The experimental results obtained from sampled d.c. polarog. (SDCP), normal pulse polarog. (NPP), differential pulse polarog. (DPP), and a.c. polarog. (ACP) with 2,2,6,6-tetramethyl-4-hydroxypiperidinyl-1-oxy; 2,2,6,6-tetramethyl-4-oxopiperidinyl-1-oxy; and 2,2,6,6-tetramethyl-piperidinyl-1-oxy in aqueous solution showed that these nitroxides can be reduced on the electrode with the formation of the corresponding hydroxylamines as their products. The half-wave potentials and the peak potentials increased with a decrease in the pH of the medium. A linear relation between the peak potentials of ACP of the nitroxides and the pH of the medium was found with a slope of -0.03 V/pH unit. The ratio between the total limiting current of NPP and that of SDCP is independent of the pH and the nitroxides studied. A heterogeneous electron transfer followed by protonation in a homogeneous medium (EC) is proposed for the reductive process.

Key words: PIPERIDINE P, AQUEOUS SOLUTION, REACTION MECHANISM, REDUCTION, PULSE POLAROGRAPHY, POLAROGRAPHIC ANALYSIS, NITRO-OXY RADICAL, SINGLE ELECTRON TRANSFER REACTION