Study On Cephalosporins With Quantum Methods

An important direction in chemistry development in the 21st century is the research on the level of molecule, which reflects that the molecular research plays more and more crucial role. Almost every process, development and design on new technology of chemical engineering are tightly connected to the systemic thermodynamic functions, therefore, it seems urgent to study the molecular thermodynamic property. In this paper, we calculate the thermodynamic functions and structural optimizations of three pharmaceutical molecules by means of quantum chemistry. In terms of the different objects, the research content is divided into three parts. Firstly, the vibration analysis and structural optimization is implemented on 7-amino-3-deacetoxycephalo-sporanic acid (7-ADCA) by dint of B3LYP method of the Density Function Theory (DFT) with the basis sets of STO-3G (5D, 7F), 3-21G (6D, 7F) and 6-31G (6D, 7F) respectively. Then we have three sets of frequencies of IR spectrum, which are compared with experimental data, and structural parameters and atomic net charges of 7-ADCA. We achieve the values of enthalpy, Gibbs energy and entropy of formation of 7-ADCA, moreover, we correct them. In the end we learn the difference between the dimensional configurations and electric charge distribution of 7-ADCA with three different basis sets. Secondly, DFT at the level of B3LYP/3-21G*, AM1 and PM3 methods have been employed to achieve the IR spectrum of cefuroxime axetil. The frequencies by calculations have been contrasted with those by experiment and then the errors are obtained. The method with the minimum error is used to calculate the values of enthalpy, Gibbs energy and entropy of formation of cefuroxime axetil and optimize its configuration。 Finally, B3LYP method of DFT with the basis set of STO-3G (5D, 7F), AM1 and PM3 methods have been applied to achieve the IR spectrum of cefaclor. The frequencies by calculations have been contrasted with those by experiment,thus, we can attain three errors. Next we make use of the method with the minimal error to calculate the values of enthalpy, Gibbs energy and entropy of formation of cefaclor and optimize its configuration. In a word, in this paper we achieve several thermodynamic functions of 7-ADCA, cefuroxime axetil and cefaclor, and optimize their dimensional configurations and atomic charge distributing. These results have indicative and theoretic meaning in the directions of the study on the property, synthesizing, and application.