Studies of the electrochemical reduction of 4-nitrophenol in dimethylformamide: evidence for a change in mechanism with temperature

The electrochemical reductions of 4-nitrophenol, 2-cyanophenol and 4-cyanophenol were studied in dimethylformamide (DMF) at gold microdisk electrodes at elevated temperatures up to 110°C. It was inferred that there is a change in mechanism for the reduction of 4-nitrophenol near 25°C. Over the entire temperature range 4-nitrophenol is reduced to the corresponding radical anion, with subsequent rapid protonation by the parent molecule to form a radical species. At temperatures above 25°C it appears that this species can undergo further electrochemical reduction at the gold electrode, introducing a new voltammetric reduction wave, contrasting the response observed at platinum