Abstract A series of novel substituted-azo dyes 8-(aryldiazenyl)quinolin-5-ol (5a-i) were synthesized by the coupling reaction 5-hydroxyquinoline with diazotized aniline derivatives in presence NaNO2 HCl/H2O mixture. The study spectroscopic and solvatochromic properties performed FT-IR, 1H 13C-NMR UV-Visible spectroscopies. tautomerism these was studied using deuteration technique measurements....