The Stability Constants and Thermodynamic Parameters of Borate - Carbohydrate Complexes by pH Measurements

Abstract

The complexation of borate with carbohydrates was studied potentiometrically at  temperatures 298.15-328.15K in aqueous medium at constant ionic strength, I = 0.1M  KCl. The stability constants (?) and thermodynamic parameters of borate-carbohydrate  complexes were determined using the technique proposed by Verchere and Hlaibi.  Carbohydrates such as D-fructose, D-Sorbitol, D-Mannitol, D-Galactose, D-Glucose and  D-Raffinose were used as ligands in this study. The ?₁ values for the complexes at  different temperatures were found to follow the order: D-fructose > D-Sorbitol > DMannitol > D-Galactose > D-Glucose > D-Raffinose. The ?G⁰ values were found to be  negative and the negative values increased according to the above order. The values of  ?H⁰ and ?S⁰ were both negative which indicated that the complex formation was an  exothermic process and the spontaneity of its formation is driven by enthalpic  contribution overcoming the negative contribution of ?S⁰.

DOI: http://dx.doi.org/10.3329/jbcs.v25i1.11766

Journal of Bangladesh Chemical Society, Vol. 25(1), 15-20, 2012