EVIDENCE FOR THE HIGHLY OXIDIZING PROPERTIES OF NO2- APPLICATION TO THE STUDY OF NITROGEN OXIDE( AND NO+ IONS IN ORGANIC MEDIA )LI CELLS/

The contamination of oxygenated nitrogen compounds dissolved in an org anic medium containing impurities represents a serious ambiguity in al l previous studies concerning the electrochemical properties of nitrog en oxides. Some of these ambiguities result also from the questionable purity of the nitrogen oxides used. In an attempt to overcome these p roblems, we have constructed and studied cells of the type graphite/ni trogen oxide-0.75 M LiClO4-organic solvent/Li in which high contents o f nitrogen oxides permit water effects to be neglected (the solvent us ed were sulfolane and propylene carbonate). The cell equilibrium poten tial(E) and the examination of the discharge curves have allowed us to account for the highly oxidizing characteristics of NO2+ ions, E(NO2/Li)=4.8 V, in comparison with NO+ ions, E(NO+/Li)=4.2 V. This finding agrees with our previous electrochemical studies on nitryl and nitros yl salts in anhydrous aprotic media, e.g. standard potentials E(NO2+/N O2.)=+1.350 V and E(NO+/NO)=+0.715 V vs. the half-wave potential of a ferrocene solution at the Pt electrode. Furthermore, the medium effect s on the NO+/NO and NO2+/NO2 couples have been examined in various sol vents chosen for their distinctive polar character. The results have b een compared with those reported previously and discussed. In addition , since the contamination of nitrogen oxides with water is the subject of numerous debates, we have reviewed the electrochemical characteris tics of some nitrogen oxides in anhydrous organic media, and compared the results with those obtained when the medium contains aliquots of w ater.