Thermochemical study of equilibria in the Cu2+-D,L-threonine system in an aqueous solution

The heats of interaction of Cu²⁺ ions with D,L-threonine in an aqueous solution were determined by direct calorimetry at ionic strengths of 0.50, 0.75, 1.00 (KNO₃) and temperatures of 288.15, 298.15, and 308.15 K and the corresponding heats of dilution were found. In calculation of the equilibrium composition of the system, side protolytic processes were taken into account along with the complexation reactions. The standard heats of formation of the CuThr⁺ and CuThr₂ species were found. The results were analyzed on the basis of Gurney views. The standard enthalpies of formation of complex species in the hypothetical undissociated state in an aqueous solution were calculated.