K. Mahmudov, R. A. Rahimov, M. Babanly
Aug 1, 2011
Citations
0
Influential Citations
25
Citations
Journal
Journal of Molecular Liquids
Abstract
Abstract The structural, tautomeric and acid–base properties of the new 1-phenyl-2-(2-hydroxy-3-sulfo-5-chlorophenylhydrazo)butane-1,3-dione (H2L1), 1-phenyl-2-(2-hydroxy-3,5-disulfophenylhydrazo)butane-1,3-dione (H2L2), 1-phenyl-2-(2-hydroxy-3-sulfo-5-nitrophenylhydrazo)butane-1,3-dione (H2L3) and 1-phenyl-2-(2-hydroxy-4-nitrophenylhydrazo)butane-1,3-dione (H2L4) were studied using IR, 1H and 13C NMR spectroscopies and potentiometry. The study reveals that H2L1–4 and the known 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H2L5) exist in solution as a mixture of Z-enol-azo-II and hydrazo-III tautomeric forms and that an increase in the solvent polarity shifts the tautomeric balance to the enol-azo form. The thermodynamic parameters of the proton dissociation in H2L1–5 were determined showing that this process is unspontaneous, endothermic and entropically unfavorable.