论文部分内容阅读
乙二胺四乙酸二钾盐的晶体属于空间群C_(2h)~5·晶胞参数:a=9.08(?),b=18.99(?),c=9.75(?),β=94°2·晶胞内含有4{K_2H_2[C_10N_2O_8]·2H_2O}。 由所收集的二千多个独立的衍射数据计算了三维帕特逊函数。根据由帕特逊函数导出的八个钾原子的位置,用最小值函数的图解重迭法成功地直接引出了绝大多数轻原子。结构最后用差值函数法确定少数轻原子的参数和进行修正,并得到电子密度函数p(x,y)、p(y,z)、p(x,z)的验证。 结构分析表明:EDTA分子对二个钾离子中的一个实行了弱螯合,采取了‘螯而不抱’的结合形式;分子构象介于非螯合的伸展构象与强螯合的顺式构象之间。 结构分析证实了N—H……O分子内氢键的存在。由于氮原子对质子的俘获和分子对质子的螯合作用,EDTA分子电离质子的机理得到了满意的说明。
The crystal of dipotassium salt of ethylenediaminetetraacetic acid belongs to the space group C 2h ~ 5. Cell parameters: a = 9.08 (?), B = 18.99 (?), C = 9.75 · Unit cell contains 4 {K_2H_2 [C_10N_2O_8] · 2H_2O}. The three-dimensional Patterson function is calculated from the collected data of more than 2000 independent diffraction. According to the positions of the eight potassium atoms derived from the Patterson function, the graphically overlapping method with the minimum function successfully leads directly to the vast majority of light atoms. In the end, the parameters of a few light atoms are determined and modified by the difference function method, and verified by the electronic density function p (x, y), p (y, z), p (x, z). Structural analysis shows that: EDTA molecule weakly chelates one of the two potassium ions and takes the form of a chelate without embracing; the molecular conformation is between the non-chelating stretching conformation and the strongly chelating cis-conformation between. Structural analysis confirmed the presence of hydrogen bonds in the N-H ... O molecule. Due to the capture of protons by nitrogen atoms and the chelation of molecules to protons, the mechanism by which EDTA molecules ionize protons has been satisfactorily described.