苯及其衍生物的密度泛函理论研究

Study on Density Functional Theory of Benzene and Its Derivatives

采用密度泛函理论B3LYP/6-31G*方法对苯及其衍生物进行结构优化,并对其稳定性、电荷布局、振动频率进行分析讨论。结果表明:当苯环上的一个氢被-CH3、-NH2、-OH、-OCH3取代后,其结构稳定性依次增强;邻对位碳原子具有较高的负电荷,所以邻对位易于发生亲电取代反应;取代基为-CH3的C-H伸缩振动向短波方向移动,-NH2、-OH、-OCH3使C-H伸缩振动向长波方向移动。找到了苯及其衍生物之间存在的规律,为实验研究提供理论指导。

Density functional theory B3LYP with 6 -31 G basis set has been used to optimize the geometries of benzene and its derivatives. Tile stability, Mulliken charges and vibrational frequencies have been investiga- ted. The results show that stability is intensive when the benzene ring is replaced by - CH3 , - NH2 , - OH, - OCH3. Electrophilie substitution could occur in ortho - position carbon and para - position carbon which have higher negative charge. C - H stretching vibration will move toward the short wavelength with - CH3 substituent. And C - H stretching vibration will move toward the long wavelength with - NHz, - OH, - OCH3. The regularity between benzene and its derivatives has been found, thus providing theoretical guid- ance for experimental research.