Dissociative Electron Transfer, Substitution, and Borderline Mechanisms in Reactions of Ketyl Radical Anions. Differences and Difficulties in Their Reaction Paths
Dissociative Electron Transfer, Substitution, and Borderline Mechanisms in Reactions of Ketyl Radical Anions. Differences and Difficulties in Their Reaction Paths
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羰基阴离子反应中的离解电子转移、取代和边界机制。
DOI：
10.1021/ja971105d
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发表时间：
1997
影响因子：
15
通讯作者：
H. Schlegel
中科院分区：
文献类型：
--
作者：
S. Shaik;D. Danovich;G. Sastry;A. Ayala;H. Schlegel
对与甲基氯反应的酮基阴离子和氯代烷基阴离子ω(CH2)NC(H)O-·(n=2，3)的计算研究发现了相互竞争的机制： 离解电子转移(ET)机制和导致C-烷基化产物的取代(子(C))机制。H(CN)CO-·/CH_3Cl明确地通过亚(C)机理进行，而ω-氯代烷基阴离子通过ET机理进行，但对H(CN)CO-·/CH_3Cl的机理的解释取决于用于探索该途径的坐标系。Z矩阵内部坐标中最陡峭的下降路径导致了ROHF/6-31G*和UHF/6-31G*级别的ET乘积。在受限的开壳HARTREE−Fock表面上产生ET产物，而在无限制的HARTREE−Fock表面上产生次(C)产物。在质量加权超高频路径上出现了一个指向ET产物方向的谷型−脊拐点，表明势能面向ET产物方向分支。
Computational studies on ketyl anion radicals with methyl chloride and on ω-chloroalkanal radical anions, Cl(CH2)nC(H)O-• (n = 2, 3), find competing mechanisms: a dissociative electron transfer (ET) mechanism and a substitution (SUB(C)) mechanism leading to a C-alkylation product. H(CN)CO-•/CH3Cl proceeds unequivocally via the SUB(C) mechanism, and ω-chloroalkanal radical anions proceed by the ET mechanism, but the interpretation of the mechanism for H2CO-•/CH3Cl depends on the coordinate system used to explore the path. The steepest descent path in Z-matrix internal coordinates leads to the ET product at both the ROHF/6-31G* and UHF/6-31G* levels. The mass-weighted path leads to the ET product on the restricted open-shell Hartree−Fock (ROHF) surface but to the SUB(C) product on the unrestricted Hartree−Fock (UHF) surface. A valley−ridge inflection point heading in the direction of ET products was located on the mass-weighted UHF path, indicating that the potential energy surface branches toward ET produ...