The enthalpies of solution of glycine in aqueous solutions of urea,formamide,acetamide,DMSOand acetone were measured at298.15 K by a RD496-Ⅲ microcalorimeter.The transfer enthalpies(ΔtrH) ofglycine from water to aqueous organic mixtures were derived and interpreted qualitatively with structural hydra-tion interaction model.The results suggest that hydrophilic-hydrophilic interaction between glycine and cosol-vent molecule gives a negative contribution to the transfer enthalpies of glycine,while the hydrophilic hydro-phobic interaction makes a positive contribution.The relative position ofΔtrH-composition profiles viz.urea
利用Anton Paar DMA 55精密数字密度计测定了L-丙氨酸在LiNO3,NaNO3,KNO3和NaClO4水溶液中的密度,计算了L-丙氨酸的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积、理论水化数和体积作用系数.根据静电相互作用和结构水合作用模型讨论了阴离子和阳离子对迁移偏摩尔体积的影响.结果表明,L-丙氨酸在四种含氧酸盐水溶液中的迁移体积均为正值,并且随着盐浓度的增大而增大.L-丙氨酸两性离子端基和阴阳离子间的静电作用对迁移体积的贡献是主要的.静电作用削弱了两性离子带电中心对周围水分子的电致收缩效应,造成了理论水化数随溶液浓度的增加而减小.L-丙氨酸在NaNO3,KNO3和NaClO4水溶液中迁移体积的不同主要是由于静电作用的不同引起的,在LiNO3水溶液中迁移体积的“反常”是由于结构相互作用的影响较大所致.
Densities of glycine,L-alanine and L-serine in various aqueous D-xylose solutions were measured at 298.15 K by an Anton Paar Model 55 densimeter.Apparent molar volumes,limiting partial molar volumes and hydration numbers for these amino acids were calculated.The transfer volumes from water to aqueous(D-xylose) solutions were obtained and discussed in terms of the structural hydration interaction model.The results show that all of the transfer volumes are positive,and increase with increasing xylose concentration;the side-chain contributions to the transfer volumes are highly related to the nature of side-chain groups;the hydration numbers for the three amino acids in solutions decrease with increasing xylose concentration.
