Yun-Yun Liu, Fang-Zhou Qiu, Jun Zhu, Yi Ren, Kai-Chung Lau
College of Chemistry and Key State Laboratory of Biotherapy, Sichuan University, Chengdu, 610064, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry and Department of Chemistry, Xiamen University, Xiamen, 361005, China.
J Mol Model. 2017 Jun;23(6):192. doi: 10.1007/s00894-017-3351-7. Epub 2017 May 20.
The modified G4(MP2) method was applied to explore microsolvation effects on the reactivity of four solvated normal oxy-nucleophiles YO(CHOH) (Y = CH, CH, FCH, ClCH), and five α-oxy-nucleophiles YO(CHOH) (Y = HO, CHO, F, Cl, Br), in gas-phase S2 reactions towards the substrate CHCl. Based on a Brønsted-type plot, our calculations reveal that the overall activation barriers of five microsolvated α-oxy-nucleophiles are obviously smaller than the prediction from the correlation line constructed by four normal microsolvated ones to different degrees, and clearly demonstrate the existence of an α-effect in the presence of one or two methanol molecule(s). Moreover, it was found that the α-effect of the mono-methanol microsolvated α-nucleophile is stronger than that of the monohydrated α-nucleophile. However, the α-effect of YO(CHOH) becomes weaker for Y = HO and CHO, whereas it becomes stronger for Y = F, Cl, Br than that of YO(HO), which can be explained by analyses of the activation strain model in the two cases. It was also found that the rationale about the low ionization energy of α-nucleophile inducing the α-effect was not widely significant. Graphical abstract Variation of alpha-effect in the gas-phase S2 reaction with the microsolvation.
采用修正的G4(MP2)方法，研究了在气相S2反应中，四个溶剂化的普通氧亲核试剂YO(CHOH) (Y = CH, CH, FCH, ClCH)和五个α-氧亲核试剂YO(CHOH) (Y = HO, CHO, F, Cl, Br)与底物CHCl反应时的微溶剂化效应。基于布朗斯特型图，我们的计算表明，五个微溶剂化的α-氧亲核试剂的整体活化能垒明显小于由四个普通微溶剂化亲核试剂构建的相关线的预测值，不同程度地清楚地证明了在存在一个或两个甲醇分子时α-效应的存在。此外，发现单甲醇微溶剂化α-亲核试剂的α-效应比单水合α-亲核试剂的更强。然而，对于Y = HO和CHO，YO(CHOH)的α-效应变弱，而对于Y = F、Cl、Br，其α-效应比YO(HO)的更强，这可以通过对这两种情况的活化应变模型分析来解释。还发现α-亲核试剂低电离能诱导α-效应的原理并不具有广泛的意义。图形摘要 气相S2反应中α-效应随微溶剂化的变化。
