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

The reactions of aniline and its derivatives at the 7-position of 4,6-dinit robenzofuroxan (DNBF) may result in rapid reaction via the nitrogen centre to give anionic sigma-adducts. Equilibrium constants for these reactions in DMSO are reported and correlate with pK(a) values of the corresponding ani linium ions. Slower reactions are observed involving electrophilic substitu tion by DNBF at ring-carbon atoms of the aniline derivatives; rate constant s are reported. These reactions produce zwitterionic carbon-bonded sigma-ad ducts which, in the presence of excess aniline, are in rapid equilibrium wi th deprotonated forms. Equilibrium constants for this acid-base process hav e been measured and indicate that the negatively charged DNBF moiety is ele ctron withdrawing relative to hydrogen.