Kinetic and equilibrium studies of the ambident reactivity of aniline, and some derivatives, towards 4,6-dinitrobenzofuroxan†‡

Abstract

The reactions of aniline and its derivatives at the 7-position of 4,6-dinitrobenzofuroxan (DNBF) may result in rapid reaction via the nitrogen centre to give anionic σ-adducts. Equilibrium constants for these reactions in DMSO are reported and correlate with pK_a values of the corresponding anilinium ions. Slower reactions are observed involving electrophilic substitution by DNBF at ring-carbon atoms of the aniline derivatives; rate constants are reported. These reactions produce zwitterionic carbon-bonded σ-adducts which, in the presence of excess aniline, are in rapid equilibrium with deprotonated forms. Equilibrium constants for this acid–base process have been measured and indicate that the negatively charged DNBF moiety is electron withdrawing relative to hydrogen.