A pulse radiolytic study of aqueous solutions containing nitrobenzene and methylviologen

Solutions containing 2-propanol, nitrobenzene (NB), and methylviologen (MV²⁺) have been studied in wide ranges of concentrations and pHs. The two radicals NB^- and MV⁺ are formed by the reactions of NB and MV²⁺, respectively, with both the hydrated electron and the 2-propanol radical. Studies were carried out at 578 nm where only the MV⁺ absorbs light. The decay of MV⁺ follows a single second-order process whose fate constant depends on [NB], [H⁺], and [MV²⁺]. Our findings could be explained by a fast equilibrium between the viologen and nitrobenzene redox systems followed by a slow reaction between MV⁺ and either NB^- or its acidic form NBH.