7-氨基-3-去乙酰基头孢烷酸的密度泛函研究

为了确定STO-3G、3-21G、6．31G三个基组是否适用于7-氨基-3-去乙酰基头孢烷酸(简称7-ADCA)，以及计算其热力学函数，本文用密度泛函理论的B3LYP方法分别在STO一3G、3-21G、6—31G水平上对7一ADcA进行红外光谱计算、能量计算和结构优化。将得到的三组红外光谱波数与实验值进行比较分析，发现3—21G和6—31G基组得到的数据比较可靠。得到的能量参数用于计算7一ADCA的一些热力学函数，例如标准生成热、生成吉布斯自由能和标准熵，并对结果进行校正。比较三个基组优化出的7-ADCA的结构，发现3—21G和6—31G基组得到的结果相近，而与STO．G相比有一些出入。这些分析结果有助于7-ADCA合成头孢药物的研究。

Analysis on the 7-amino-3-deacetoxycephalosporanic acid with the application of density functional theory

The objective of this article is established to make sure whether the bases set of STO-3G,3-21 G and 6-31 G areapplicable to the 7-amino-3-deaeetoxycephalo-sporauic acid(7-ADCA)or not and to calculate its thermodynamic func-tions.The B3LYP method of the Density Function Theory is employed on the 7-ADCA to calculate the IR spectrum andenergy parameters and optimize geometry,respectively at the level of STO-3G,3-21G and 6-31G.The frequencies calculat-ed with the basis set of STO-3G,3-21G and 6-31G are contrasted with the experimental frequencies and it is found that theparameters with the basis sets of 3-21G and 6-31G are more credible than those with the basis set of STO-3G.We achievethe thermodynamic functions of 7-ADCA with the energy parameters,such as enthalpy,Gibbs free energy and entropy offormation,and correct these values.Compared the structures of 7-ADCA optimized with the three basis sets,we find thatthe result of 3-21G basis set and that of 6-31G basis set are very parallel.These results are available for researching thepreparation of eephalosporin in virtue of 7-ADCA.