Elektronendonator-Akzeptor-Komplexe von Diazonium-Ionen und die Struktur von stabilisierten Diazonium-Salzen. 20. Mitteilung zur Kenntnis der Azokupplungsreaktion

1. In 0.1N HCl/H₂O, o- and p-nitrobenzenediazonium ions rapidly form a complex with 2-naphthol-6, 8-disulphonic acid anions. Visible and NMR, spectra show that it has the structure of a charge-transfer complex (π-complex). The latter is probably an intermediate in the electrophilic aromatic substitution (diazo coupling reaction). 2. Diazonium ions form charge-transfer complexes with naphthalene, 1-methylnaphthalene, naphthalene-1-sulphonic acid, 1-naphthyl-methanesulphonic acid and also 2-naphthol-1-sulphonic acid. The equilibrium constants of all these complexes have been determined. 3. The stabilisation of diazonium salts by arylsulphonic acids with regard to decomposition is due to charge-transfer complex formation and not to formation of diazosulphonates as assumed by former investigators. The sulphonic group is not essential for the stabilisation. 4. Charge-transfer complex formation decreases the electrophilicity of the diazonium ion (rate of diazo coupling reaction) only slightly.