Szabó István, Olasz Balázs, Czakó Gábor
Department of Chemistry, King's College London , London SE1 1DB, United Kingdom.
Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged , Rerrich Béla tér 1, Szeged H-6720, Hungary.
J Phys Chem Lett. 2017 Jul 6;8(13):2917-2923. doi: 10.1021/acs.jpclett.7b01253. Epub 2017 Jun 14.
Due to their importance in organic chemistry, the atomistic understanding of bimolecular nucleophilic substitution (S2) reactions shows exponentially growing interest. In this publication, the effect of front-side complex (FSC) formation is uncovered via quasi-classical trajectory computations combined with a novel analysis method called trajectory orthogonal projection (TOP). For both F + CHY [Y = Cl,I] reactions, the lifetime distributions of the F···YCH front-side complex revealed weakly trapped nucleophiles (F). However, only the F + CHI reaction features strongly trapped nucleophiles in the front-side region of the prereaction well. Interestingly, both back-side and front-side attack show propensity to long-lived FSC formation. Spatial distributions of the nucleophile demonstrate more prominent FSC formation in case of the F + CHI reaction compared to F + CHCl. The presence of front-side intermediates and the broad spatial distribution in the back-side region may explain the indirect nature of the F + CHI reaction.
由于双分子亲核取代（S2）反应在有机化学中的重要性，对其进行原子层面的理解展现出呈指数增长的研究兴趣。在本出版物中，通过准经典轨迹计算结合一种名为轨迹正交投影（TOP）的新颖分析方法，揭示了前侧复合物（FSC）形成的影响。对于F + CHY [Y = Cl, I]反应，F···YCH前侧复合物的寿命分布揭示了弱捕获的亲核试剂（F）。然而，只有F + CHI反应在前反应阱的前侧区域具有强捕获的亲核试剂。有趣的是，后侧和前侧攻击都显示出形成长寿命FSC的倾向。与F + CHCl相比，在F + CHI反应中亲核试剂的空间分布表明FSC形成更为显著。前侧中间体的存在以及后侧区域广泛的空间分布可能解释了F + CHI反应的间接性质。
