β-环糊精及其衍生物与酚酞的包结行为研究

Complexation Reaction Between β-cyclodextrin with Its Derivatives and Phenolphthalein

由于β-环糊精与酚酞的结合平衡常数很大,理论研究表明用差光谱Hildebrand-Benesi方程的计算结果会比实际偏小。改进了Hildebrand-Benesi方程在β-环糊精包结酚酞上的使用,获得的实验结果与理论相符。并研究了pH值、甲醇浓度、离子强度对β-环糊精包结酚酞的影响,计算得到包结平衡常数。结果显示,包结平衡常数随pH值、甲醇浓度的升高而减小,随离子强度的增大而增大。证明疏水作用是驱使酚酞分子进入β-环糊精空腔的重要驱动力。比较了β-环糊精及其衍生物包结酚酞的能力,结果表明边臂上的不同功能基团影响很大。

The association constant of β-cyclodextrin （β-CD） including phenolphthalein （PP） is very large, and the results of theoretical study show that association constant calculated by the Hildebrand-Benesi equation would be smaller than that obtained in the experiments. In the paper, the Hildebrand-Benesi equation is developed in the complexation reaction between β-CD and PP, and therefore, the experiment results are identical to theoretical study. The effects of pH, solvent and ionic strength on equilibrium constants are investigated by the developed equation. The results indicate that association constants decrease with the increasing of pH and concentration of methanol while they increase with the increasing of sodium chloride concentration. The results suggest that hydrophohic interaction is an important driving force in the inclusion reaction. In addition, the inclusion abilities of β-CD with its four derivatives to PP are compared and the results show that the substituted groups on the borders have a great effect on the inclusion abilities of β-CD.