Kinetics of protonation of the 1,2-dinitrobenzene radical anion and dianion by phenol

The kinetics of protonation of electrochemically generated 1,2-dinitrobenzene (1,2-DNB) radical anions and dianions by phenol in DMF was studied by chronoamperometry. In the presence of phenol, the rate-determining step of electroreduction at the first wave potentials is the protonation of the 1,2-DNB radical anion with a rate constant of 103 +/- 13 L mol(s-1) s(s-1). The number of electrons involved in the process with phenol excess is 3, which corresponds to the formation of azoxy compounds. At the second wave potentials under these conditions, the electroreduction process is four-electron, which corresponds to the formation of 2-nitrophenyl-hydroxylamine, The rate constant for 1,2-DNB dianion protonation is 265 +/- 60 Lmol(s-1) s(s-1). The comparison of the experimental data with the results of quantum chemical calculation suggests the orbital control of the protonation reaction.