Asymmetric identity S(N)2 transition states: Nucleophilic substitution at alpha-substituted carbon and silicon centers

作者：Rocha Marcus V J; Smits Nicole W G; Wolters Lando P; de Cozar Abel; Guerra Celia Fonseca; Ramalho Teodorico C; Bickelhaupt F Matthias

来源：International Journal of Mass Spectrometry, 2017, 413: 85-91.

DOI：10.1016/j.ijms.2016.06.003

• Density functional calculations
• Nucleophilic substitution
• Silicon
• Substituent effects
• Reaction mechanisms

We have quantum chemically investigated the archetypal nucleophilic substitution reactions at carbon (SN2@C) and at silicon (SN2@Si) in the model reaction systems Cl- +A(CH3)2(CH2X)CI (A= C, Si; X= H, F, Cl, Br, I) using relativistic density functional theory (DFT) at ZORA-OLYNTZ2P. Our purpose is twofold. We wish to understand: (i) how the alpha-substituent X affects S(N)2 reactivity; and (ii) how methyl substituents at the central electrophilic atom A exactly participate in the transition vector of the Walden inversion. Interestingly, despite the fact that our SN2 model reactions are symmetric, i.e., constitute identity reactions, they proceed via slightly asymmetric transition states. We have also explored competing E2 pathways.

• 出版日期2017-2