The concentration dependences of the stability constants of iodine-iodide-amylose complexes in aqueous solutions of electrolytes

摘要

The thermodynamic characteristics of complex formation between iodine-iodide particles and amylose in aqueous solutions of electrolytes (LiCl, KCl, CsCl, KNO3, and CaCl2) at 298.15 K were studied by potentiometry. The equilibrium constants for this process (log K (1)) were determined. The temperature dependences (T = 283.15-313.15 K) of the constants in solutions of KCl and CaCl2 were used to calculate the enthalpy and entropy of complex formation. Different electrolyte effects on the ionic strength dependence of log K-1 In were explained by the competition between the I-3(-) and I2Cl- ions for entering the amylose helix cavity and the influence of electrolytes on the interphase distribution of these ions and the solvation state of the low-molecular-weight reagents, amylose, and complexes in solution.