3种黄酮醇类化合物核磁共振碳谱的理论研究

在B3LYP/6-31G水平下优化了3种黄酮醇类（山奈酚，槲皮素，杨梅素）化合物的几何构型. 在振动分析中，均未出现虚频率. 在B3LYP/6-31G的水平下计算了该类化合物的核磁共振碳谱. 研究结果表明：3种分子均有分子内氢键形成，且分子内氢键的键长为0.17~0.18 nm左右 . 本文讨论了羟基引入之后对邻近C的化学位移的影响. 从取代基对NMR的影响来看，随着取代基对苯环的供电子能力的加强，取代基邻近的一些C的化学位移有所改变. 

A Theoretical Study on Nuclear Magnetic Resonance Spectra of Three Flavonol Derivatives

The configurations of the title compounds were optimized at the B3LYP/6- 31G level. The results show that there is no imaginary frequency in the vibrational analysis. The 13C NMR spectra of the compounds were studied at the same level by the GIAO method. The calculated results show that there exist intramolecular hydrogen bonds in the three flavonol derivatives, and the bond lengths are estimated to be about 0.17- 0.18 nm. The effects of hydroxyl substituents on the chemical shifts of the adjacent carbons are also discussed. It appears that the more donated electrons from the substituent groups to benzene, the larger the chemical shifts of the adjacent carbons will change.