Abstract The rearrangements of 4′-methoxy-N-methyl-and N-methyl-4′-nitro- diatzoaminobenzene have been studied in 20% acetonitrile/aqueous buffers. The reactions are specifically acid catalyzed and involve pre-equilibrium formation of amine and diazonium salt followed by rate-limiting attack of the diazonium ion at a C-atom (C-coupling) to give the corresponding aminoazo compounds. There is no evidence to suggest that, ...