Nitration of Phenol and Aniline Derivatives : Role of Nitrous Acid

Abstract

WHILE nitrous acid (we include in this term all material that with water gives nitrous acid) is a negative catalyst in aromatic nitration generally, it has often been found to be a positive catalyst in the nuclear nitration of phenol and aniline derivatives. New experiments, mainly with phenol derivatives, have lessened the contrast by showing that, in the nitration of these substances, both positive and negative catalysis may be encountered in different ranges of nitric acid concentration, and that the negative catalysis is quite similar to that appearing in the nitration of aromatic compounds of other types. Nevertheless it is clear that certain special mechanisms, dependent on nitrous acid, intervene in the nitration of phenol and aniline derivatives, and we have been attempting to throw some light on their nature by a study of the kinetics and products of the nitration of these compounds.