摘要
采用ab initio方法,在HF/6-31G水平上对4种酚类抗氧剂的平衡几何构型、净电荷及前线轨道组成和能级等进行了理论计算研究,探讨了这些化合物的结构特征、抗氧化活性和取代基效应。研究表明,这些抗氧化剂HOMO和LUMO均为π-分子轨道。由共轭大π-键的离域性和HOMO与LUMO的性质表明,不饱和的共轭体系不仅能与自由基结合,还因共轭体系的孤对电子更易转移而与金属形成配位键和化学吸附膜,添加剂的电子结构性质决定了抗氧作用。研究还表明酚类化合物的抗氧化活性与其释放活泼氢生成苯氧自由基的能力有关,活性大小与O-H间的Mulliken集居数、净电荷差、前线轨道能级和反应终态能量下降量有关。4种酚类化合物的抗氧化活性:化合物Ⅰ>Ⅳ>Ⅱ>Ⅲ,与实验结果一致。
Molecular geometry , atomic net charge, constituents and energy of frontier molecular orbital for four phenol antioxidant have been calculated by ab initio method at the 6-31G basis set level. Structural characteristics, antioxidative activities and substituent effect are investigated. It is found that HOMO and LUMO of four compounds are RRR-molecular orbital with lone pare electrons. Based on the delocalization property of conjugation system and activity of HOMO and LUMO, it is predicted that unsaturated conjugation system can be combined with radical and reacted with metal. The lone pair electrons of HOMO for antioxidant translates easily to LUMO of metal to form coordinate bond and chemical adsorption film. The antioxidative function of additives can be shown from the electron configuration characteristics. The free radical scavenging activity of four compounds are related to their capability of generating phenoxyl free radical after H-abstraction from phenol antioxidant. The antioxidative activities of four compounds have a bearing on their O-H Mulliken electron population, the difference of atomic net charge, frontier orbital energy and the decreased energy at the ending state. Therefore, the calculated results indicated that the order of the antioxidative activities for four compounds is the following: Ⅰ>Ⅳ>Ⅱ>Ⅲ, which is in good agreement with the antioxidative order reported in the experimental results.
出处
《计算机与应用化学》
CAS
CSCD
北大核心
2005年第4期287-290,共4页
Computers and Applied Chemistry
基金
国家自然科学基金项目(50005018)湖南省自然科学基金项目(02JJY2019)湖南省中青年科技基金项目(01 JZY2099)
关键词
酚类抗氧化剂
从头计算
结构-活性
前线分子轨道理论
phenol antioxidant, ab initio, structure-activity, frontier molecular orbital theory
