The polarographic reduction of N-nitrosoderivatives of aliphatic, cycloaliphatic and aromatic amines has already been the subject of various studies. While some of them are mainly of analytical character I -5,15 in others attempts have been made to elucidate, although incompletely and qualitatively, the mechanism of the electrode reduction of the =N-N=O group and to establish the influence of the molecular skeleton on the reducibility of this group 6-11.
Martin and Tashdijan 6, for example, consider the process as controlled by diffusion, although considering the possibility of a more complicated control. According to Lund 8, the electroreduction of N-nitroso compounds is irreversible and diffusion controlled both in strong acid and alkaline media, involving respectively 4 and 2 electrons. At intermediate pH, the nature of the rate-determining step has not been established. In alkaline medium the reduction products are said to be a secondary amine and N20. Holleck and Schindler 9 consider that the process takes place through a hydroxylamine intermediate, which is also the reduction product in alkaline medium. In acid medium the electrolysis product is the corresponding hydrazine. Polarographic and spectroscopic studies on various N-nitrosoamines led Zharadnik et al. 11 to propose a mechanism involving kinetic complications.
It remains therefore to establish the nature and the details of the electroreduction mechanism of this class of compound, which are important, inter alia, for the electrochemical preparation of asymmetric hydrazines, which are of interest for their biological activity, etc. EXPERIMENTAL Di-n-propyl-N-nitrosoamine (DNPNA) was prepared by the method of Lemal et al. 12. The product used had the following physical properties: b.p. 90ยฐC/ 13 Torr; n~5= 1.44165; d~5=0.91101 ; ~25=33.8014. The ir spectrum was identical with that reported by Tarte 13. Dielectric and vapour pressure measurements 14,16 excluded the possibility of dimerization equilibria.
The supporting electrolyte consisted of Britton-Robinson buffer containing 20~ by volume of EtOH. Below pH 2 the measurements were made in H2SO4 containing 20 ~o of EtOH. All the products used were of analytical grade.
The polarographic measurements were carried out in a three electrode cell