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

Abstract

Abstract 1. In 0.1N HCl/H 2 O, 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.