SINGLE-ELECTRON TRANSFER IN AROMATIC NUCLEOPHILIC-SUBSTITUTION ON DINITROBENZONITRILES

Reaction of OH- with 3,5-dinitrobenzonitrile in water or water-DMSO gives a mixture of unproductive 2- and 4-Meisenheimer complexes that equilibriate and eventually form 3,5-dinitrobenzamide and finally the benzoate ion. The corresponding reaction of 2,4-dinitrobenzonitrile gives the 5-Meisenheimer complex and then a mixture of 2,4-dinitrobenzamide and 2,4-dinitrophenoxide ion. The ratio amide:phenoxide ion increases with increasing [OH-]. These reactions appear to involve formation of charge-transfer complexes of the radical anion of the substrate and .OH which collapse to give Meisenheimer complexes and final products. The rate constants of the various reaction steps can be estimated by simulation based on relaxation theory, which also fits the product mixture from 2,4-dinitrobenzonitrile. This reaction scheme is consistent with observations of exchange of arene hydrogen and of extensive broadening of H-1 NMR signals of the substrates during reaction.