The reduction of hydrazones is generally suggested to proceed through a reductive Cleavage of the nitrogen nitrogen bond followed by a reduction of the carbon-nitrogen bond. This sequence of reduction processes is here supported for fluorenone (V) and benzophenone (VI) hydrazones as well as by a comparison of the reduction of fluorenone and benzophenone hydrazonium ions (I,III) with corresponding imines (II,IV). Another proof of the presence of imines its intermediates is the splitting of four-electron waves of hydrazones V and VI and hydrazonium ions I and VIII into two waves at pH < 2. This, has been interpreted as due to differences in slopes dE(1/2)/dpH and pK(a)-values of protonated hydrazine derivatives on one side and corresponding imines on the other. In this pH-range imines formed in reductions of VI and VIII are reduced in a single two-electron wave. those of I and V in two one-electron steps. Fluorenone imine (II) is sufficiently stable to allow recording of time-independent current-voltage curves between pH 6 and 11. In this pH-range the imine (II) is reduced in two one-electron steps, Benzophenone imine (IV) has been found stable between pH 4.6 and 12. At pH 4.6-8 the reduction of the imine IV takes place in a single two-electron step, at pH 8-12 in two one-electron steps, Final proof of the initial cleavage of the N N bond is presented by comparison with the reduction of nitrones. (c) 2005 Elsevier Ltd. All rights reserved.