Comparison Study for Stability Constants of Azo-dyes Produced from The Reaction of Tetracycline with Two Diazotized-reagents at Different pH

Our research focused on a spectroscopic study of the stability constants of the formation of two azo dyes prepared from the reaction of tetracycline with two different diazotized reagents and at three acidic medias: acidic, neutral and basic, and at a constant temperature (288K). We studied the optimal conditions for each prepared azo-dye, as well as the optimal mole-ratios for its components, which were (1:1) for (drug: reagent)”.We determined the stability constants of the two prepared azo-dyes at the three acidic media and at the five temperatures (283, 293, 303, 313 and 323K). After that, we studied the factors that affect the values of its stability constants, which are; The effect of temperature: We calculated the stability constants at the five temperatures mentioned above, and it became clear from them that the formation reactions of azo-dyes are spontaneous and exothermic, from the negative values of(DG° and DH) respectively, and also the negative value of (DS°) supports the aforementioned.The effect of the pH-function: We found the stability constants for each of the prepared dyes at each pH and at different temperatures, so we obtained the values of the stability constants, which were evidence of the preparation of stable azo-dyes”.The effect of structures: It was found that the difference in the structural formula of the diazotized-reagent has a clear effect on the values of the stability constants for the formation of the prepared azo-dyes, and this was proven through the variation in the values of the stability constants”.