尿嘧啶及其衍生物溶解焓的影响因素探讨

On the Influencing Factors of Dissolution Enthalpy of Uracil and its Derivatives

在298.15K、一个大气压下,用密度泛函数在B3LYP/6-31+G*水平上利用PCM(Polarizable continuum model)极化连续模型模拟尿嘧啶,5-氟-尿嘧啶,5-氯-尿嘧啶,5-溴-尿嘧啶和5-三氟-尿嘧啶溶入甲醇和水中的焓值.计算所得尿嘧啶及其卤素衍生物在水中的溶解焓与实验值一致,但尿嘧啶及其卤素衍生物在甲醇中的溶解焓与实验值差别较大.由此分析了分子在两种溶剂中的氢键、电子密度拉普拉斯值以及它们的π键的影响,结果表明溶于甲醇溶液的氢键键能偏大,电子密度拉普拉斯值以及分子的π键与实验结果有良好的相关性.

Density functional at B3LYP/6-31＋G＊level was used to explore the enthalpies when uracil,5-fluorine uracil,5-chloro-uracil,5-bromo-uracil and 5-（triflu）-uracil is dissolved in methanol and water at 298.15 Kand 1atmospheric pressure.The calculated enthalpies of dissolution of uracil and its derivatives in water are in agreement with the experimental values,but they are very different in methanol.Therefore,the paper analyzes the molecular hydrogen bond,Laplacian of electron density and the influence ofπof the molecules in two solvents.The results show that the hydrogen bond dissolved in methanol solution can be too large,the electron density value and Laplacian of electron density andπbond electron has good correlation with experimental results.