IMPEDANCE ANALYSIS OF THE MECHANISM FOR NITROMETHANE REDUCTION IN AQUEOUS-SOLUTIONS - THE INFLUENCE OF PH

The faradaic impedance for nitromethane reduction on mercury in aqueou s solutions of different pH values in the range pH 2-8 is analyzed wit h the equations previously derived for an electron reduction followed by a chemical step mechanism with two diffusing intermediates (EC-C-E mechanism). The reaction parameters for the first one-electron reducti on and for the second three-electron reduction an studied as a functio n of pH, The results can be explained if a branched mechanism includin g two parallel EC (electron reduction and chemical reaction) sequences is assumed for the first reduction and a CECee sequence for the secon d reduction. The use of an equivalent resistance circuit to deduce the kinetic equations for different possible branched mechanisms is prese nted.