NMR法研究Na+在二元混合溶剂中的溶剂化(Ⅱ)

本文测定了NaBPh_4在CH_3OH-CH_3COCH_3, CH_3OH-CH_3CN, DMSO-DMF, DMSO-HCONH_2混合溶剂体系中~(23)Na~+的化学位移随溶剂组成的变化规律。利用Covington模型计算了四个混合溶剂体系中一种溶剂B对另一种溶剂A的优先溶剂化自由能。同时利用等溶剂化点法比较了各种溶剂对Na~+的溶剂化能力。两种方法得出的相对溶剂化能力为: 对甲醇体系二种方法皆为CH_3OH>CH_2-COCH_3>CH_3CN。对DMSO体系, Covington模型: DMSO>HCONH_2>DMF; 等溶剂化点法: DMSO=HCONH_2>DMF 实验结果表明: 在二元混合溶剂体系中一种溶剂对阳离子的溶剂化能力的大小除了与其本身的特性有关外, 还与共同构成二元系的另一种溶剂的性质有关。

A STUDY ON THE SOLVATION OF Na+ IN BINARY MIXTURE OF SOLVENTS BY Na-23 NMR (Ⅱ)

~(23)Na~+ chemical shifts of NaBPh_4 in mixed solvents of CH_3OH-CH_3COCH_3, CH_3OH-CH_3CN, DMSO-DMF, DMSO-HCONH_2 were measured. By means of isosolvation point the solvating abilities were compared. Meanwhile the data were treated quantitatively to obtain a geometric equilibrium constant, K~1/n, and the free energy of preferential solvation, △G/n, as outlined by Covington. According to the results, the relative solvating abilities of the solvents were found to be: CH_3OH>CH_3COCH_3>CH_3CN, DMSO=HCONH_2>DMF by iso-solvation point and DMSO>HCONH_2>DMF by ΔG/n.The order indicates that the solvating ability of one solvent in binary mixture depends not only on its own nature, but also on character of cosolvent and structure of binary mixture.