Synthesis of some new azo dyes derived from 4-hydroxy coumarin and spectrometric determination of their acidic dissociation constants

A series of azo coumarin dyes was synthesized by the coupling of 4-hydroxy coumarin and diazonium salts, which obtained by diazotization of aniline and aniline derivatives. The azo dyes were characterized by IR, 1HNMR and UV-Visible spectra. The acid dissociation constants, Ka, of the dyes were determined using electronic spectroscopic method. Substitutions effect on this parameter was reported and discussed.