Substituted Aniline Acid And Its Complex Stability Constant Determination And Calculation Of The Thermodynamic Functions

At isothermal condition, by pH titration, stability constant of three succinanilic acid compounds: (COOCH2CH2CONHC6H5, COOCH2CH2CONH-(2-OCH3)C6H4, COOCH2CH2 CONH-(4-OC2H5)C6H4) and two phthalanilic acid compounds: 2-COOC6H4CONHC6H5,2-COOC6H4CONH-(2-OCH3)C6H4 at three different temperature were determined. At the same condition, by the same way, the stability constant of their binary and tribasic nickel complexes were determined and the corresponding thermodynamic function were calcula-ted. The stability constant of the binary complexes of cadmium and the five ligand acid were also determined at 293.15K. Because of the induction effect and the conjugative effect that produced by substituting group -OCH3, -OC2H5, the value of stability constant of substituted anilic acid decreased with the increasing density of electronic cloud of reaction center, but the value of stability constant of binary and tribasic complexes were increased . The stability constant of binary complexes of cadmium and nickel at 293.15K were taken as the example to illustrate the linear relationship between the binary complexes and the corresponding ligand acid. The possibility of effecting this relationship is discussed.