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首页> 外文期刊>Bulletin of the Chemical Society of Japan >Thermal Isomerization at a C=N Double Bond:How Does the Mechanism Vary with the Substituent?
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Thermal Isomerization at a C=N Double Bond:How Does the Mechanism Vary with the Substituent?

机译：C = N双键的热异构化：机理如何随取代基变化？

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摘要

Thermal isomerizations at the C=N double bonds in R_1R_2C=NC_6H_4X proceed via an inversion mechanism,in which the C=NC_6H_4X bond angle is near 180 deg at the transition state(TS).Available experimental data on the reactions of(CF_3)_2C=NC_6H_4X and YC_6H_4CH=NC_6H_4X have suggested that the reaction mechanism changes with substituent X.In the present study,HF,B3LYP,and MP2 computations were carried out to analyze the modes of mechanistic change with the substituent for the reactions of(CF_3)_2C=NC_6H_4X,YC_6H_4CH=NC_6H_4X,and other systems.There are two possible pathways within the inversion mechanistic framework:a planar pathway with the R_1R_2C=N double-bond plane and the aromatic ring being coplanar at the TS and a perpendicular one with the two planes being perpendicular to each other at the TS.It was found that the mechanistic change is not due to a change in the relative importance of two independent and competitive reaction pathways,but arises from a change of the character of a single TS from planar to perpendicular geometry when the substituent becomes more electron-withdrawing.
机译：R_1R_2C = NC_6H_4X在C = N双键处的热异构化是通过反演机理进行的，其中C = NC_6H_4X键角在过渡态（TS）处接近180度。（CF_3）_2C反应的可用实验数据= NC_6H_4X和YC_6H_4CH = NC_6H_4X表明反应机理随取代基X的变化而变化。在本研究中，进行了HF，B3LYP和MP2的计算，以分析（CF_3）_2C反应的机理。 = NC_6H_4X，YC_6H_4CH = NC_6H_4X和其他系统。在反转机制框架内有两种可能的途径：具有R_1R_2C = N双键平面的平面途径和芳香环在TS处共面且与两者垂直的途径研究发现，机理的变化不是由于两个独立的竞争性反应途径的相对重要性的变化，而是由于分子特征的变化引起的。当取代基变得更吸电子时，从平面几何结构到垂直几何结构的单个TS。

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