The protonation of anthracene anion radical by phenol

This reaction was studied by Amatore and Sav ant [88] using DPSC. Pseudo-first-order kinetics for the reaction in the presence of excess phenol was implied from the observation of dEp/d log v close to 30 mV decade-1 during LSV analysis. The objective of the study was to show that the eCeh, where the subscript refers to a homogeneous reaction, rather than the eCe mechanism is followed. The substrate and phenol concentrations were invariant at 10-3 and 10-2 M, respectively. A more extensive study using both DPSC and DCV by Ahlberg and Parker [50] supported the mechanism assignment. Thus, at that point it appeared that the data could be accounted for by the mechanism 

A more detailed LSV study [58, 89] resulted in the conclusion that the kinetics, under all conditions, could not be described by the simple eCej, scheme. It was proposed that the reaction order in anthracene anion radical (AN- ) varies between 1 and 2 and the reaction order in phenol is greater than 1. A complex mechanism was also indicated from DCV measurements [89]. At a phenol concentration of 10 mM, values of dEpj d log v were in all cases close to that expected for a reaction second order in An-, i.e. 19.5mV decade-1 under the conditions of the experiments. The process is fast enough under these conditions for it to be expected to fall well within the KP zone. That this is the case was indicated by the fact that d p/dlog v was linear over a reasonably wide range of v (10— 1000 mV s-1). The highest value of the slope, observed at a phenol concentration of 100mM, was still significantly lower than 29.3 mV decade -1 predicted for a pseudo-first-order reaction. 

The conclusions of these studies were disputed by Saveant and coworkers [90] who claimed that the data are indeed consistent with the simple eCeh mechanism and implied that the previous interpretation was influenced by experimental error. More recently [91], they re-examined the data and found that it was necessary to propose a somewhat more complex mechanism involving reactions of AN- complexed with either one or two molecules of PhOH. 

LSV data for the reduction of anthracene in N, JV-dimethyl-formamide in the presence of phenol and phenoxide iona 

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