Université de Lyon, CNRS (UMR5182), Université Lyon 1, école Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
Phys Chem Chem Phys. 2012 May 21;14(19):7170-5. doi: 10.1039/c2cp40438a. Epub 2012 Apr 10.
Depending on the selected DFT functional, two different mechanisms are found for two organic reactions (an intramolecular nucleophilic aromatic substitution and a nucleophilic addition on a carbonyl moiety). Indeed, B3LYP predicts a concerted mechanism whereas M06-2X foresees a multistep one. Calculations at the MP4(SDQ) level proved the mechanisms to be stepwise. We studied these reactions with a large panel of exchange-correlation functionals and demonstrated that the amount of exact exchange is of first importance. For some borderline cases, the form of the functional has also an impact, e.g. the Meisenheimer σ-adduct of the intramolecular nucleophilic aromatic substitution can be located with B3PW91 but not with B3LYP. These results stress the need to use recently proposed functionals to investigate chemical reactivity.
根据所选的 DFT 函数，两种不同的机制被发现适用于两种有机反应（分子内亲核芳香取代和羰基上的亲核加成）。实际上，B3LYP 预测协同机制，而 M06-2X 则预测多步机制。在 MP4(SDQ)水平上的计算证明了这些反应是分步进行的。我们用大量的交换相关泛函研究了这些反应，并证明了精确交换的数量非常重要。对于一些边界情况，函数的形式也有影响，例如，分子内亲核芳香取代的 Meisenheimer σ-加合物可以用 B3PW91 定位，但不能用 B3LYP 定位。这些结果强调了需要使用最近提出的泛函来研究化学反应性。
