1144. The rearrangement of aromatic N-nitroamines. Part IV. The intramolecularity of the acid-catalysed rearrangements of N-nitro-1-naphthylamine and its N-methyl homologue

Abstract

The acid-catalysed rearrangements of the above-mentioned compounds have bcen studied at various aciditics in the presence of l5N-label1ed nitric and nitrous acids. The rearrangement products contained no detectable tracer. These observations, together with the results of experiments with added scavengers, exclude mechanisms involving fission to ionic or radical species followed by intermolecular recombination of the counter-fragments.THE formation of C-nitro-products from the acid-promoted rearrangement of N-nitroarylamines is generally considered to be intramole~ular,~-~ but few substrates have been adequately studied over a range of reaction conditions, and in one example an intermolecular component of rearrangement has been claimed.5 Various methods can give information on this point, but each has its limitations if taken as an isolated criterion.We have studied the rearrangements of N-methyl-N-nitro-l-naphthylamine and Nnitro-l-naphthylamine, using a combination of methods to enable a decision concerning the intra-or inter-molecularity to be reached. Analogies with previous work l s 5 suggest that intermolecular mechanisms may be especially favoured for these substrates. RESULTSTracer E=cperimeizts.-Reactions were carried out in the presence of 15N-labelled nitric and nitrous acids a t different acidities. The only rearrangement products were the 2and 4-nitroderivatives, and a dinitro-derivative under one set of conditions. These products were isolated, purified, and examined for tracer-uptake by mass spectrometry. Results are in the Table . The error in the abundance measurements was & @ l o in the units quoted for experiments 1-3, and f0-15 for experiment 4.Attempts to simulate the condition of experiment 1 f a i l d for N-rdro-l-naphthylamine ; rearrangement was negligible but much tar was formed. This seems a characteristic fate if

Nitro derivatives of 1,3-dihydrobenzimidazol-2-one: II. Rearrangement of N-nitrobenzimidazol-2-ones

“…Low acid concentration favors tarring. The authors presumed [12][13][14][15][16][17] that the rearrangement is intramolecular.…”

“…It is known that [12][13][14][15][16][17] aromatic N-nitro amines, such as N-nitroaniline and N-nitropyridin-2-amine, in aqueous solutions of strong acids undergo rearrangement involving migration of the nitro group into the aromatic ring. The major products of this rearrangement are the corresponding ortho-nitro derivatives, though some amounts of para-nitro derivatives were also detected.…”