四甲基脲与水二元混合体系的拉曼光谱研究

Study on the 1,1,3,3-Tetramethylurea-Aqueous Binary System by Raman Spectrometry

密度泛函B3LYP方法在6-311G*基组水平对四甲基脲(TMU)气态的几何构型进行全面优化,计算了最优构型的拉曼光谱,并与实验得到的拉曼光谱进行比较,对TMU的各拉曼谱带进行归属。实验测得了TMU与水不同体积比二元混合体系的拉曼光谱,得到了TMU分子的特征拉曼谱线在不同浓度下的频移情况,受氢键和缔合水分子空间位阻的共同作用,在H2O/TMU体积比小于2时,TMU羧基伸缩振动频率向低波数的变化与体积比成线性关系,当体积比大于2时,其振动频率为定值1585cm-1,其它拉曼带的频率受到溶剂的非专一化作用而随溶液中水的增加变化不大。

The DFT（density functional theory） method was used to optimize and calculate the geometry struc-ture of 1,1,3,3-tertramethylurea （TMU） molecular and Raman frequency in the level of 6-311G＊ basis set. Meanwhile, in order to make the Raman assignments to the TMU molecular, the calculated TMU Raman frequency was compared with its Raman frequency that was measured in experiment. The frequent shift of TMU-aqueous binary solution at different concentration was measured by Raman method. Under the influence of special interactions （ hydrogen band） and steric hindrance of the associated water molecule ; when this ratio was lower than 2, the frequency changes of stretching vibration of carboxyl in TMU was linear proportion to this ratio ; when this ratio was larger than two, the frequency of stretching vibration of carboxyl was a constant at 1585cm^-1. Under the influence of non-special interactions of solvent effects, other vibration frequency change was small.