Substituent effects of positive poles in aromatic substitution. Part V. Variation in the substituent effect of the –NH3+ group in aromatic nitration

Abstract

As the acidity of the medium is decreased, the yield of meta-substitution in the nitration of anilinium salts decreases, and that of both ortho- and para-substitution increases; over the range 98–82% sulphuric acid, the yield of meta-substitution falls from 62% to 36%. An analysis of the rate profiles for substitution at these positions together with the effect of N-deuteriation on the reaction rate shows that the change in the orientation of substitution is not a consequence of reaction through the aniline molecule or of proton loss from the nitrogen pole during reaction. It appears instead to derive from differential salt effects on substitution at the ortho-, meta,- and para-positions in the anilinium ion.