Physikalisch‐chemische Eigenschaften und Elektronenstruktur der Azo‐Verbindungen. Teil X: Über die Protonierung der Azo‐Gruppe in p′‐ oder m′‐substituierten Derivaten des p‐Dimethylamino‐azobenzols

The absorption spectra and relative basicities of p‐dimethylamino‐azobenzene and of ten of its p′‐ or m′‐substituted derivatives have been determined. The bathochromic shift of the long‐wave π → π*‐transition on protonation of the azo link and the pK′1 values for this particular acid‐base equilibrium have been compared with the respective values found previously for correspondingly substituted phenylazoazulenes.