Voltammetry in the absence of excess supporting electrolyte – ECE-DISP1 reactions: The electrochemical reduction of 2-nitrobromobenzene in acetonitrile solvent

Electrochemical reactions where the variation of supporting electrolyte concentration is mechanistically revealing: ECE-DISP1 processes in which the chemical step is an isomerisation

“…The result at high support, (c sup = 100), agrees with previously published working curves of the ECE/DISP1 mechanism [34], with, for a given value of K f , the ECE mechanism producing a slightly higher current in the transition region from n eff = 1-2 than the DISP1 mechanism. These highly supported curves are the same for this 'isomerisation' mechanism as the results for any other ECE/DISP1 mechanism, such as the reduction of halonitrobenzenes discussed above [16]. As the support ratio is lowered, however, it is seen that, in this case where there is no fragmentation in step 9, the difference becomes less, and at very low support ratios DISP1 produces a higher current in this transition stage.…”

“…At discussed in previous work [16]. In the case of the ECE mechanism, a crossover effect can be seen on the reverse wave which becomes more apparent when as the value of K f becomes of the order of r, rationalised as follows.…”

“…This investigation uses a model based on this, with homogeneous kinetics included, also developed previously [1,16]. Table 2.…”

“…Weakly supported voltammetry has also been used to attempt to elucidate the reduction mechanism of 2-nitrobromobenzene [16]. The mechanism is known to be of ECE/DISP1 type, but unlike the mechanism discussed later in this paper, has a chemical step that involves a fragmentation:…”

Recent Advances in Voltammetry

“…While DISP2 is able to be distinguished from the other mechanisms with relative ease, the discrimination between ECE and DISP1 is difficult . At high concentrations of supporting electrolyte, careful analysis of voltammetric wave shape over a range of scan rates can in some circumstances be used . At steady state, however, it is impossible to distinguish the two mechanisms.…”