Electronic absorption spectra of some analogues and derivatives of Michler's ketone

Abstract

Analogues of Michler's ketone in which the terminal groups are effectively conjugated with the aromatic system give charge-resonance systems by protonation of the oxygen atoms in acid solution. In terminally bridged ketones, tendency of the amino-nitrogen atoms to conjugate with the aromatic rings is reduced when trimethylene groups are replaced by ethylene groups. Formation of a quinonoid cation is completely inhibited by the presence of crowding substituents adjacent to a dimethylamino-group.