DMF—H2O缔合体系的^1H NMR研究

1H NMR Studies of DMF-H2O Association System

DMF水溶液是一种生物分子水溶液的简单生化模型 .测量了DMF H2 O体系不同温度下全浓度范围的1HNMR数据 ,对体系中的缔合情况进行了讨论 ,基于H2 O ,H2 O·DMF ,(H2 O) 2 和 (DMF) 2 ·H2 O的缔合平衡建立了化学缔合模型 ,采用最小二乘法拟合实验数据 ,联合遗传算法和Levenberg Marquardt算法对模型参数进行全局寻优求解得不同温度的缔合平衡常数K ,再根据不同温度的K求得缔合平衡的ΔH和ΔS .为了更好地理解DMF水溶液中分子间的相互作用 ,还测量了 2 98K下DMF CCl4和DMF BuOH体系全浓度范围的1HNMR数据作为比较 ,结合NMR的基本原理对各DMF溶液体系1HNMR的实验现象进行了分析和解释 ,认为水溶液的特殊结构、氢键和DMF酰胺基的共轭体系是影响DMF H2

Dimethylformamide (DMF) aqueous solution is a kind o f simple biochemical model of biological molecular aqueous solutions. In this pa per, ~1H NMR of DMF-H2O system was measured at different temperatures t o discuss molecular interactions in the mixtures. The association system was mo deled on the equilibrium among H2O, H2O·DMF, (H2O)2 and (DMF)2·H2O and calculated by nonlinear least-square fitting. Association equilibrium cons tant K and the corresponding ΔH and ΔS were obtained by combined G A and Levenberg-Marquardt algorithm. In addition, DMF-CCl4 and DMF-BuOH sy stems were also studied in order to further understand the nature of interaction s in DMF-water mixture. Some peculiar phenomena were found and considered to be mainly caused by the special structure of liquid water, the hydrogen-bonding i nteractions and the conjugate system of amide.