共轭效应的本质及其在有机反应中的特殊性
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摘要
共轭效应是有机化学中特别重要的电子效应之一,存在于共轭体系之中;大学有机化学教学目标要求学生掌握并能熟练应用共轭效应理论解决有机化学中的实际问题。由于共轭效应涉及微观认知,学生普遍感觉不易理解。但作为教学重点与难点,又必须掌握;同时也是学生大学毕业后继续深造学习所必须的基础理论知识,理解、掌握并能熟练应用该理论知识解决有机化学中的学习问题显得尤为重要。本文采用密度泛函理论方法计算并给出了3个二烯烃分子轨道中最高占据分子轨道(HOMO)、最低空分子轨道(LUMO)结构图,揭示了共轭体系内部因存在电荷转移现象而产生电子云的平均化本质,表现在键参数中的键长平均化变化。
Conjugate effect,existing in conjugation systems,is one of the crucial electronic effects in organic chemistry. One of the teaching objectives of organic chemistry at university stage lies in enabling students to master and skillfully apply the conjugate effect theory to solve practical problems in organic chemistry. As conjugate effect belongs to the scope of microcosmic cognition,undergraduates often have some difficult in learning this theory.However,as the main and difficult points in teaching contents,the knowledge about the conjugate effect must be grasped by undergraduates. Meanwhile,it also is the basic theoretical knowledge that graduate students need to master. Therefore,it is very important for undergraduates to understand,master and skillfully apply the knowledge about the conjugate effect. In present paper,we calculated the HOMO and LUMO of three alkadiene molecules using theoretical calculation method at DFT level. The nature of equalization for electron cloud density is derived from the charge transfer in conjugation systems,which further leads to the equalization of bond distances.
Conjugate effect,existing in conjugation systems,is one of the crucial electronic effects in organic chemistry. One of the teaching objectives of organic chemistry at university stage lies in enabling students to master and skillfully apply the conjugate effect theory to solve practical problems in organic chemistry. As conjugate effect belongs to the scope of microcosmic cognition,undergraduates often have some difficult in learning this theory.However,as the main and difficult points in teaching contents,the knowledge about the conjugate effect must be grasped by undergraduates. Meanwhile,it also is the basic theoretical knowledge that graduate students need to master. Therefore,it is very important for undergraduates to understand,master and skillfully apply the knowledge about the conjugate effect. In present paper,we calculated the HOMO and LUMO of three alkadiene molecules using theoretical calculation method at DFT level. The nature of equalization for electron cloud density is derived from the charge transfer in conjugation systems,which further leads to the equalization of bond distances.
引文
[1]王积涛,张宝申,王永梅等.有机化学(第二版).天津:南开大学出版社,2003,90.
[2]王积涛,张宝申,王永梅等.有机化学(第二版).天津:南开大学出版社,2003,91.
[3] A D Beck. J. Chem. Phys.,1993,98(7):5648~5659.
[4] C Lee,W Yang,R G Parr. Phys. Rev. B,1988,37(2):785~791.
[5] M J Frisch,G W Trucks,H B Schlegel et al. Gaussian 09,Revision B. 01,Gaussian,Inc. Wallingford CT,2010.
[6]曾昭琼主编,李景宁副主编.有机化学(上册,第四版).北京:高等教育出版社,2004,94.
[7]王永梅,王桂林编.有机化学提要·例题和习题.天津:天津大学出版社,1999,181-182.
[8]曾昭琼主编,李景宁副主编.有机化学(下册,第四版),北京:高等教育出版社,2004,205.
[9]曾昭琼主编,李景宁副主编.有机化学(下册,第四版).北京:高等教育出版社,2004,209.
[2]王积涛,张宝申,王永梅等.有机化学(第二版).天津:南开大学出版社,2003,91.
[3] A D Beck. J. Chem. Phys.,1993,98(7):5648~5659.
[4] C Lee,W Yang,R G Parr. Phys. Rev. B,1988,37(2):785~791.
[5] M J Frisch,G W Trucks,H B Schlegel et al. Gaussian 09,Revision B. 01,Gaussian,Inc. Wallingford CT,2010.
[6]曾昭琼主编,李景宁副主编.有机化学(上册,第四版).北京:高等教育出版社,2004,94.
[7]王永梅,王桂林编.有机化学提要·例题和习题.天津:天津大学出版社,1999,181-182.
[8]曾昭琼主编,李景宁副主编.有机化学(下册,第四版),北京:高等教育出版社,2004,205.
[9]曾昭琼主编,李景宁副主编.有机化学(下册,第四版).北京:高等教育出版社,2004,209.