全氟辛磺酸(PFOS)的结构、稳定性的密度泛函理论研究

Research on Density Functional Theory of Structure and Stability of Perfluorooctane Sulfonate

全氟辛磺酸因其在环境介质中的稳定性、环境持久性和生物累积性,正逐渐引起科学界的广泛关注。本研究应用Gaussian09程序,采用密度泛函理论B3LYP/6-31G(d,p)方法,对89个全氟辛磺酸(C8F17SO3H)异构体进行了结构优化及频率、吉布斯自由能及激发态的计算,通过异构体的吉布斯自由能相对大小确定各物质的相对稳定性。研究结果表明,直链全氟辛磺酸的稳定结构呈现螺旋状,由于氟原子紧密包裹在碳链外侧,C-F键键能很高,F原子间的空间位阻效应和电子效应使得89个全氟辛磺酸异构体中含有端基三氟甲基的异构体具有较高的稳定性,含有较多或较大取代基的多为不稳定异构体。

With stability, environmental persistence and bioaccumulation in environmental media, PFOS has gradually been causing widespread concerns of scientific community. The research was optimized structure and calculated frequency, Gibbs free energy as well as excited state of 89 PFOS （C8F17SO3H） isomers by using Gaussian09 program. Relative size of Gibbs free energy determined relative stability of each substance. The research result showed that stable structure of straight chain PFOS presented helical. Due to fluorine atom was tightly wrapped in the outer side of the carbon chain; bond energy of C-F was high. Steric-hinerance effect and electronic effect of F interatomic which contain TerrninalTri-fluoro-methyl,-CF3 made PFOS isomer has higher stability. PFOS isomers most were instability isomer which contained more or larger substituent.