Abstract
The visible absorption spectra of 4-(2-benzothiazolylazo)resorcinol (BTAR) and 4-(2-benzothiazolylazo)salicylic acid (BTAS) have been recorded in water-organic solvent mixtures in the pH range 0.5–12.0. The organic solvents used are methanol, ethanol,n-propanol, iso-propanol, acetone, dioxane and dimethyl formamide. The spectral changes have been explained in terms of shifts in equilibria among different molecular and ionic species of BTAR and BTAS existing in solution. The pK a values corresponding to the different ionization steps have been determined at 25°C and I=0.1M (KNO3) by graphic analysis of the absorbance-pH curves. The results obtained are discussed in terms of the molecular structure of the reagents and the nature of the organic co-solvent used.
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Abu-Bakr, M.S., El-Shahawy, A.S. & Ahmed, S.M. Spectrophotometric study of acid-base equilibria of 4-(2-benzothiazolylazo)resorcinol and 4-(2-benzothiazolylazo)salicylic acid in water-organic solvent media. J Solution Chem 22, 663–675 (1993). https://doi.org/10.1007/BF00646785
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DOI: https://doi.org/10.1007/BF00646785