An electronic spectral study of the coupled effect on the tautomeric equilibria of some α-hydroxy azo compounds

Abstract

The spectral behaviour of six a-hydroxy azo compounds has been investigated in solution. The bands appearing in the u.v. and visible regions are assigned to possible electronic transitions. Azo compounds containing pyrazolone and acetyl or ester moieties are found to exist mainly in the hydrazo form in solution, while those containing the naphthol moiety exist in the azo-hydrazone tautomeric equilibrium. The solvatochromic behaviour of the compounds is investigated by studying their spectra in organic solvents of different polarities. The acidity constants are determined from the spectra of the compounds in aqueous ethanolic solutions of varying pH values.