Diazotisation of Aromatic Primary Amines of Weak Basicity (Part 1) -Effects of Inorganic Salts-

Abstract

In order to disclose side reactions in the diazotisation of aromatic primary amines of weak basicity, the reactions of 6-bromo-2, 4-dinitrobenzenediazonium [1] and 6-chloro-2, 4-dinitrobenzenediazonium compounds C_2C'D with some inorganic salts in sulfuric acid have been investigated. In the reaction with NaNO₂, [1'] gives not only 2, 3, 5-trinitrobromobenzene but also 1, 2- dibromo-3, 5-dinitrobenzene under a preferential replacement of the -NZ group even in the absence of copper catalyst in strong sulfuric acid. In the reactions with inorganic halides (KF, NaCI, NaBr, KI), [1] gives the corresponding halogen compounds by the replacement of -N2 group except in the case of KF. The yield of the halogen compound varies in the order: FCCl < Br <I.
Similar results are obtained also in the reactions of C_2C'. The reactions of dazonium compounds derived from 2, 4-dinitroaniline, p-nitroaniline, and aniline with inorganic halides have also been carried out. However, the, yield of the corresponding halogen compound decreases with decreasing number of the nitro groups on the aromatic nucleus.
These results suggest that the replacement of -N, group in these reactions takes place by a bimolecular mechanism. Nucleophilic reagents of weak basicity and moderate nucleophilicity appear to react even in sulfuric acid with C. M and C_2C'D under a cleavage of N2 group to give the corresponding substitution products.