23223-05-4Relevant academic research and scientific papers
Tautomerism in Some Azo Dyes
Bhagwat, R. V.,Karambelkar, N. P.,Tiwari, Alok
, p. 419 - 422 (2007/10/02)
A series of azo dyes (II) has been synthesized by coupling various aryldiazonium salts with β-(4-methoxyphenyl)glutaconic anhydride (I) in aqueous acetone at pH 1.0 to 1.5.In solid state these compounds exist almost exclusively in hydrazone-form (II).Apparent dissociation constants (pKa) measured in dioxane-water (3:1) and μ=0.1M show significant correlation with Hammett's ? constants, indicating that the hydrazone-form (II) is the most predominant form in polar solvents.With the help of PMR spectroscopy in different solvents the two tautomeric forms, keto-azo (III) and keto-hydrazone (II) have been identified.The tautomerism constants (KT) show a significant correlation with Hine's ? constants.The results indicate that an electron donating substituent on the phenyl ring of hydrazone favours keto-hydrazone form (II) over keto-azo form (III) in the tautomeric equilibrium.
