丝氨酸在醇-水溶液中的溶解焓

Enthalpies of Solution of L-Serine in Aqueous Alcoholic Solutions

用RD-496III双热流精密微热量计测量了L-丝氨酸在纯水以及异丙醇、1,2-丙二醇和丙三醇水溶液中的溶解焓,并计算了从水到醇-水溶液中的迁移焓.实验发现,L-丝氨酸在水及醇-水溶液中的溶解焓都是正值,它从水到醇-水溶液中的迁移焓也都是正值,并且基本上随着醇浓度的增加而增加,说明在溶解过程中,溶质与混合溶剂分子的部分去水化吸热过程占主要地位.另外,实验还发现L-丝氨酸从水到异丙醇水溶液中的迁移焓大于在1,2-丙二醇水溶液中的,更大于在丙三醇水溶液中的,这是由于羟基的减少导致了疏水-亲水作用的增加和亲水-亲水作用的减弱.

The enthalpies of solution of L-serine were measured in water and aqueous solutions of isopropanol, 1,2-propanediol and propanetriol at 298.15 K with an RD-496Ⅲ microcalorimeter. Enthalpies of transfer （△Htrs） of L-serine from water to aqueous solutions were calculated as well. From the experimental result it was found that both the values of enthalpies of solution and enthalpies of transfer of L-serines were positive, indicating that it was endothermic. They were increased with the increasing of concentration of alcohols. Such evidence illustrated that in the process of solution the endothermic of the partial dehydration of solute and molecules of mixed solution was predominant. In addition it was also found that the enthalpies of transfer of L-serine from water to aqueous isopropanol solution is larger than that from water to aqueous 1,2-propanediol and propanetriol solution. This could be illuminated by the reinforcement of hydrophilic-hydrophobic interaction and by the weakening of hydrophilic-hydrophilic interaction.