3- nitroacetophenone anion

The following represent the resonance forms of the 3-nitroacetophenone anion ... 

They were found not to react with BESOD, the rate constant was estimated to be < 10 M s , if there was a reaction at all The reaction of BESOD was also investigated with several other radicals generated by pulse radiolysis. With the semiquinone of riboflavin 5 -phosphate no reaction was detected. The semiquinone of 9,10-anthraquinone-2-sulfonate and the radical anion of 4-nitroacetophenone converted the enzyme into an unreactive form... 

The cyclohexadienyl anion intermediate is more stable, and is formed faster, when the electron-withdrawing nitro group is ortho to chlorine. o-Chloronitrobenzene reacts faster than m-chloronitrobenzene. The measured difference is a factor of approximately 40,0(X) at 50°C. 4-Chloro-3-nitroacetophenone is more reactive, because the ring bears two powerful electron-withdrawing groups in positions where they can stabilize the cyclohexadienyl anion intermediate. 

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