苯硫酚分子内质子转移取代基效应的理论研究

在B3LYP/6-311+G(d, p)水平上研究了2-(1H-咪唑)苯硫酚(1d)、2-(噁唑)苯硫酚(2d) 、2-(噻唑)苯硫酚(3d)及其衍生物的基态质子转移过程, 探讨取代基电子效应对质子转移的影响. 结果表明: 吸电子引入后分子平面电子密度减小, N2-H1间距减小, 分子内氢键增强, 醇式到酮式质子转移能垒减小; 供电子基引入后分子平面电子密度增大, N2-H1间距增大, 分子内氢键减弱, 质子转移能垒增大. Localized orbital locator(LOL)分析表明: 取代基的引入对N1原子成键性质产生影响明显. 三者质子转移能垒大小为1d<3d<2d, 取代基引后能垒相对大小不变.

Theoretical Study On Subsituent Effects in Intramolecular Proton Transfer Processes of Thiophenols

The ground-state intramolecular proton transfer (GSIPT) reactions of 2-(1H-imidazol-2-yl) benzenethiol(1d), 2-(oxazol-2-yl) benzenethiol(2d), 2-(thiazol-2-yl) benzenethiol(3d) and their subsituent derivatives have been studied at B3LYP/6-311+G(d, p) level. The electronic effects of substituents on the intramolecular proton transfer reactions have been explored. The results show that when electron-withdrawing substituents are introduced, electron density of the whole molecular plane decreases, N2-H1 spacing decreases, intramolecular hydrogen bonding is enhanced, the proton transfer barrier from enol to keto decreases. When electron-donating substituents are introduced, electron density of the whole molecular plane increases, N2-H1 spacing increases, intramolecular hydrogen bonding is weakened, the proton transfer barrier from enol to keto increases. LOL(Localized orbital locator) function analysis reveals that substituents have significant effect on the bonding properties of atom N1. The energy barrier order of the three is 1d<3d<2d, it remains the same when substituents are introduced.