二氧六环-水体系的1H和17ONMR研究

1H and 17O NMR Study of the Dioxane-Water System

Fratiello等对二氧六环(DO)-水体系进行了变温实验,估算出一级平衡常数β=0.15—0.20/mol·dm.之后Clemett在研究环氧类化合物水溶液时,认为不能用简单的一级平衡来解释这类化合物的水合现象;Mirti和Zelano等用溶剂破坏水的氢键能力的因子(f)来衡量溶剂的性质,但未对未配位水与溶剂之间的相互作用作定量描述.本工作用配位平衡和快交换方法定量描述了DO-水体系中H和O化学位移随浓度的变化.讨论了未配位水的结构破坏程度及其存在形式.

~1H andO NMR of the dioxane (DO)-water system have been studied. The complex equilibrium constants [β=0.10/mol·dm, β=0.050/(mol·dm)~2] in this system were obtained from the ~1H. chemical shift variation of DO with its concentration. With these equilibrium constants, we calculated the equilibrium concentrations of each species in all the samples. The variations of ~1H andO chemical shifts of water were analyzed with the fast exchange method. It is found that ~1H andO chemical shifts of free water in this system is linearly related to the natural logarithm of its concentrations by the following formula:δ= 3.33 + 0.36ln[HO],δS=-10.9 + 2.72ln[HO]. The degree of structural break of water by DO was evaluated by these formulas.