Asymmetric identity SN2 transition states: Nucleophilic substitution at α-substituted carbon and silicon centers

Marcus V.J. Rocha; Nicole W.G. Smits; Lando P. Wolters; Abel de Cózar; Célia Fonseca Guerra; Teodorico C. Ramalho; F. Matthias Bickelhaupt

doi:10.1016/j.ijms.2016.06.003

Asymmetric identity S_N2 transition states: Nucleophilic substitution at α-substituted carbon and silicon centers

Marcus V.J. Rocha, Nicole W.G. Smits, Lando P. Wolters, Abel de Cózar, Célia Fonseca Guerra, Teodorico C. Ramalho, F. Matthias Bickelhaupt

Research output: Contribution to journal › Article › peer-review

16 Citations (Scopus)

Abstract

We have quantum chemically investigated the archetypal nucleophilic substitution reactions at carbon (S_N2@C) and at silicon (S_N2@Si) in the model reaction systems Cl⁻ + A(CH₃)₂(CH₂X)Cl (A = C, Si; X = H, F, Cl, Br, I) using relativistic density functional theory (DFT) at ZORA-OLYP/TZ2P. Our purpose is twofold. We wish to understand: (i) how the α-substituent X affects S_N2 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 S_N2 model reactions are symmetric, i.e., constitute identity reactions, they proceed via slightly asymmetric transition states. We have also explored competing E2 pathways.

Original language	English
Pages (from-to)	85-91
Number of pages	7
Journal	International Journal of Mass Spectrometry
Volume	413
DOIs	https://doi.org/10.1016/j.ijms.2016.06.003
Publication status	Published - 1 Feb 2017
Externally published	Yes

Keywords

Density functional calculations
Nucleophilic substitution
Reaction mechanisms
Silicon
Substituent effects

ASJC Scopus subject areas

Instrumentation
Condensed Matter Physics
Spectroscopy
Physical and Theoretical Chemistry

Access to Document

10.1016/j.ijms.2016.06.003

Cite this

@article{893f044a0c0a41318e485557bd34c853,

title = "Asymmetric identity SN2 transition states: Nucleophilic substitution at α-substituted carbon and silicon centers",

abstract = "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)Cl (A = C, Si; X = H, F, Cl, Br, I) using relativistic density functional theory (DFT) at ZORA-OLYP/TZ2P. Our purpose is twofold. We wish to understand: (i) how the α-substituent X affects SN2 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.",

keywords = "Density functional calculations, Nucleophilic substitution, Reaction mechanisms, Silicon, Substituent effects",

author = "Rocha, \{Marcus V.J.\} and Smits, \{Nicole W.G.\} and Wolters, \{Lando P.\} and \{de C{\'o}zar\}, Abel and \{Fonseca Guerra\}, C{\'e}lia and Ramalho, \{Teodorico C.\} and Bickelhaupt, \{F. Matthias\}",

note = "Publisher Copyright: {\textcopyright} 2016 Elsevier B.V.",

year = "2017",

month = feb,

day = "1",

doi = "10.1016/j.ijms.2016.06.003",

language = "English",

volume = "413",

pages = "85--91",

journal = "International Journal of Mass Spectrometry",

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TY - JOUR

T1 - Asymmetric identity SN2 transition states

T2 - Nucleophilic substitution at α-substituted carbon and silicon centers

AU - Rocha, Marcus V.J.

AU - Smits, Nicole W.G.

AU - Wolters, Lando P.

AU - de Cózar, Abel

AU - Fonseca Guerra, Célia

AU - Ramalho, Teodorico C.

AU - Bickelhaupt, F. Matthias

PY - 2017/2/1

Y1 - 2017/2/1

N2 - 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)Cl (A = C, Si; X = H, F, Cl, Br, I) using relativistic density functional theory (DFT) at ZORA-OLYP/TZ2P. Our purpose is twofold. We wish to understand: (i) how the α-substituent X affects SN2 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.

AB - 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)Cl (A = C, Si; X = H, F, Cl, Br, I) using relativistic density functional theory (DFT) at ZORA-OLYP/TZ2P. Our purpose is twofold. We wish to understand: (i) how the α-substituent X affects SN2 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.

KW - Density functional calculations

KW - Nucleophilic substitution

KW - Reaction mechanisms

KW - Silicon

KW - Substituent effects

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DO - 10.1016/j.ijms.2016.06.003

M3 - Article

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