氨基酸在水或氯化钾水溶液中体积性质的研究

A Study on Volumetric Properties of the Amino Acid in Water or in Aqueous Potassium Chloride

在298.15K和常压下利用密度法测定了十几种α-氨基酸在水或氯化钾水溶液中的表观摩尔体积,由此得到了各氨基酸的偏摩尔体积和其相应的转移偏摩尔体积,以及氨基酸中侧链对其偏摩尔体积的贡献值.从理论上计算了各氨基酸在上述溶液中的水化数和体积相互作用参数.结果表明,氨基酸的转移偏摩尔体积值随着盐溶液浓度的增加而增大;氨基酸与共溶质间的相互作用以1∶1形式为主;氨基酸的水化数随盐浓度的增加而减小.对所得结果进行了定性讨论.

The apparent molar volumes, φ_v, of some α-amino acids in aqueous solutions and four various molalities potassium chloride solutions were determined from precise density measurements with a DMA 602 digital density meter at ordinary pressure and 298.15K. Partial molal volumes, V°, have been also evaluated from the apparent molar volumes in various solute concentrations. These data have been used to calculate the partial molar volumes of transfer of amino acids from water to aqueous potassium chloride solutions and the contributions of the side-chain in amino acid to partial molal volumes of amino acids in water and po■ssium chloride aqueous solutions, respectively. The number of water molecules hydrated to amino acid and volumetric interaction coefficients were calculated. The results indicate: the partial molar volumes of transfer of amino acids increase with increasing the molality of potassium chloride; 1:1 interaction between amino acid and KCl in solutions is dominant; the hydration number decrease with the increasing of potassium chloride molality. A qualitative discussion is given.