Study of the stability constants of a number of aromatic azo-chalcone dyes through their reaction with the reagent para-phenylenediaminetetraacetic acid

Younis, Asmaa Mohamed; Hussin, Mohammed Mahmood

doi:10.33899/berj.2025.187025

	Study of the stability constants of a number of aromatic azo-chalcone dyes through their reaction with the reagent para-phenylenediaminetetraacetic acid
College Of Basic Education Research Journal
Volume 21, Issue 1, March 2025, Pages 634-650 PDF (1.27 M)
Document Type: Review Paper
DOI: 10.33899/berj.2025.187025
Authors
Asmaa Mohamed Younis^* ; Mohammed Mahmood Hussin^*
Department of Chemistry, College of Education for Pure Sciences, University of Mosul, Iraq
Abstract
The research included a thermodynamic spectroscopic study of five azo dyes prepared from the reaction of five different chalcones with the reagent (nitrogenous para-phenylenediamine) at their natural pH. Optimal conditions were found for each dye, and the optimal molar ratio (2:1) of nitrogenous reagent:chalcone was studied for all the dyes prepared at temperatures (372, 382, 392, 313, and 323) K. The degree of agglomeration (α) or degree of dissociation was then determined, from which the stability constant of the resulting dye was calculated. When applying the Van't Hoff integral equation, negative enthalpy values (∆H) were obtained, indicating that the reaction is exothermic. This is confirmed by the decrease in the stability constant when the reaction temperature increases. The free energy of gypsum (∆G) was also calculated, and its value was negative, which is expressed by the following equation: (∆G=-RTLnK). The entropy (∆S), which was also negative, indicates an increase in the regularity of the resulting substance when compared to the reactants of chalcone with the reagent para-phenylenediaminetetraacetic acid.

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