Electrophilic substitution. Part IV. Kinetics of the nitration of acetophenone, benzamide, benzoic acid, and NN-dimethylaniline N-oxide in aqueous sulphuric acid

Abstract

The nitrations of NN-dimethylaniline N-oxide and of benzamide in 81–93% sulphuric acid proceed through their conjugate acids. Up to acidities at least as high as that represented by ca. 90% sulphuric acid, benzoic acid and acetophenone are nitrated as the free bases. An investigation of the dependence on temperature of the extent of protonation and of the rate constant for nitration of acetophenone permits direct evaluation of the Arrhenius pre-exponential factor for the reaction of the free base (log A_fb= 10·1 ± 1·0); the result is in accord with the postulated free base mechanism, in contrast to similar results for certain heterocyclic N-oxides.

Isomer proportions for the nitration of acetophenone are reported and discussed.