摘要
前文曾报导用离子选择电极研究铜(Ⅱ)-α-氨基酸体系的稳定常数logK_(CuL),但此法不能测定第二级稳定常数logK_(CuL_2)。为深入研究其线性热力学函数关系,本文用PH电位法测定铜(Ⅱ)-α-氨基酸体系配合物在25、35及45℃logK_(CuL)~t和logK_(CuL_2)并分别求得在上述温度时配合物的自由能变化(△G_(CuL)和G_(CuL_2))、生成焓(△H_(CuL)和△H_(CuL_2))及生成熵(△S_(CuL)和△S_(CuL_2))研究结果表明,上述氨基酸配合物(CuL和CuL_2)的稳定性与配位体碱性强度之间均成线性自由能关系;配合物的生成焓与配位体的加质子焓△H_L~之间也存在着线性关系。
In this paper, the stability constanls of coordination compounds formed from aminoacids: DL-Serine, DL-Valine, DL-Alanine and α-amino-isobutyric acid with Cu(Ⅱ) are determined by pH-Potentiometry at 25℃, 35℃ and 45℃ in the presence of 0.16 mol·L^(-1) KNO_3. The linear free energy relations not only exist between the stability comstants of Cu (Ⅱ)-aminoacid coordination compound with the base strength of ligands, but also exist between tbe formation enthalpy of coordination compounds with the protnaton enthalpy of the ligands, it can be represented by the linear equation. 25-45℃, △H_CuL_2=3. 37△H_L+113, r=0. 999.
