The Study Of Thermodynamics Properties Using Quantum Chemistry

Some new methods have been applied in Chemistry more and more deeply with the development of computer science and elevation of computing rate. Computation using Quantum Chemistry was carried out in this paper, and a predicting model for predicting the infinite dilution activity coefficient , an important parameter in thermodynamics. Then we provide the important theoretical basis of isoflavone separation by calculating their structures.In the first place, computation of geometry structure of more than 300 kind of chemical substances were carried out using STO-3G and 3-21G from ab initio and AM1 and PM3 from semi-empirical method. Then the microstructure properties of those chemical substances were obtained. The infinite dilution activity coefficient of different kind of substances were made regression, and prediction equations were obtained. Then different methods were compared in predicting the infinite dilution activity coefficient.Additionally, three kind of isoflavone, such as genistein, daidzein and glycitein, which are the functional component of soybean, were calculated by using molecular mechanics methods. The relations between volume of isoflavone and the properties of solution, such as solubility parameter and critical pressure, have been obtained. The influences of molecular bond length and bond angle on molecular volume were also analyzed. Those provide theoretical basis for using what kind of membrane and solvent for membrane separation of isoflavone. And these results also lay a foundation of building a model of oil phase membrane separation.Generally speaking, a new and simple way of predicting the infinite dilution activity coefficient was suggested in this paper. We provide a theoretical basis for separation of isoflavone practically, on which we can choose suitable solvent for extracting isoflavone, which has specified volume, according to given membrane separation, or choose membrane with suitable pore size according to different solvent and concentration for separation. Thus we can decrease our experimental work and raise our efficiency. Those provide a new idea for our future researches.