Ab initio molecular dynamics studies on substitution vs electron transfer reactions of substituted ketyl radical anions with chloroalkanes

How do the two products form in a borderline mechanism?

Hiroshi Yamataka, Misako Aida, Michel Dupuis

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

We present a qualitative analysis, based on ab initio molecular dynamics (MD) calculations, of the SN2/ ET mechanistic spectrum for three reactions: (1) HC(CN)=O.- + CH3Cl, (2) HC(CN)=O .- + (CH3)2CHCl and (3) H2C=O .- + CH3Cl, passing through their SN2-like transition states. Finite temperature (298 K) direct MD simulations indicate that the trajectories for reaction (1) appear to have a propensity towards SN2 products, the propensity for trajectories for reaction (2) seems to be towards ET products, whereas trajectories for reaction (3) appear to show no particular propensity towards either ET or SN2 products. The mechanistic diversity is consistent with the electron-donating ability of the ketyl species and steric bulkiness of chloroalkanes. We find that the trajectories have characteristics that reflect strongly the types of process [SN2 trajectories in reactions (1) and (3) vs ET trajectories in reactions (2) and (3)]. Trajectories that lead to SN2 products are simple with C-C bond formation and C-Cl bond breaking essentially completed within 50 fs. By contrast, trajectories leading to ET products are more complex with a sudden electron reorganization taking place within 15-30 fs and the major bonding changes and electron and spin reorganizations completed after 250 fs.

Original languageEnglish
Pages (from-to)475-483
Number of pages9
JournalJournal of Physical Organic Chemistry
Volume16
Issue number8
DOIs
Publication statusPublished - Aug 2003

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Anions
Molecular dynamics
electron transfer
Substitution reactions
Trajectories
trajectories
substitutes
molecular dynamics
anions
Electrons
products
electrons
qualitative analysis
Computer simulation
simulation

Keywords

  • Borderline mechanism
  • Direct molecular dynamics simulation
  • Electron transfer
  • MO calculations
  • S2
  • Transition state

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry

Cite this

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title = "Ab initio molecular dynamics studies on substitution vs electron transfer reactions of substituted ketyl radical anions with chloroalkanes: How do the two products form in a borderline mechanism?",
abstract = "We present a qualitative analysis, based on ab initio molecular dynamics (MD) calculations, of the SN2/ ET mechanistic spectrum for three reactions: (1) HC(CN)=O.- + CH3Cl, (2) HC(CN)=O .- + (CH3)2CHCl and (3) H2C=O .- + CH3Cl, passing through their SN2-like transition states. Finite temperature (298 K) direct MD simulations indicate that the trajectories for reaction (1) appear to have a propensity towards SN2 products, the propensity for trajectories for reaction (2) seems to be towards ET products, whereas trajectories for reaction (3) appear to show no particular propensity towards either ET or SN2 products. The mechanistic diversity is consistent with the electron-donating ability of the ketyl species and steric bulkiness of chloroalkanes. We find that the trajectories have characteristics that reflect strongly the types of process [SN2 trajectories in reactions (1) and (3) vs ET trajectories in reactions (2) and (3)]. Trajectories that lead to SN2 products are simple with C-C bond formation and C-Cl bond breaking essentially completed within 50 fs. By contrast, trajectories leading to ET products are more complex with a sudden electron reorganization taking place within 15-30 fs and the major bonding changes and electron and spin reorganizations completed after 250 fs.",
keywords = "Borderline mechanism, Direct molecular dynamics simulation, Electron transfer, MO calculations, S2, Transition state",
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T1 - Ab initio molecular dynamics studies on substitution vs electron transfer reactions of substituted ketyl radical anions with chloroalkanes

T2 - How do the two products form in a borderline mechanism?

AU - Yamataka, Hiroshi

AU - Aida, Misako

AU - Dupuis, Michel

PY - 2003/8

Y1 - 2003/8

N2 - We present a qualitative analysis, based on ab initio molecular dynamics (MD) calculations, of the SN2/ ET mechanistic spectrum for three reactions: (1) HC(CN)=O.- + CH3Cl, (2) HC(CN)=O .- + (CH3)2CHCl and (3) H2C=O .- + CH3Cl, passing through their SN2-like transition states. Finite temperature (298 K) direct MD simulations indicate that the trajectories for reaction (1) appear to have a propensity towards SN2 products, the propensity for trajectories for reaction (2) seems to be towards ET products, whereas trajectories for reaction (3) appear to show no particular propensity towards either ET or SN2 products. The mechanistic diversity is consistent with the electron-donating ability of the ketyl species and steric bulkiness of chloroalkanes. We find that the trajectories have characteristics that reflect strongly the types of process [SN2 trajectories in reactions (1) and (3) vs ET trajectories in reactions (2) and (3)]. Trajectories that lead to SN2 products are simple with C-C bond formation and C-Cl bond breaking essentially completed within 50 fs. By contrast, trajectories leading to ET products are more complex with a sudden electron reorganization taking place within 15-30 fs and the major bonding changes and electron and spin reorganizations completed after 250 fs.

AB - We present a qualitative analysis, based on ab initio molecular dynamics (MD) calculations, of the SN2/ ET mechanistic spectrum for three reactions: (1) HC(CN)=O.- + CH3Cl, (2) HC(CN)=O .- + (CH3)2CHCl and (3) H2C=O .- + CH3Cl, passing through their SN2-like transition states. Finite temperature (298 K) direct MD simulations indicate that the trajectories for reaction (1) appear to have a propensity towards SN2 products, the propensity for trajectories for reaction (2) seems to be towards ET products, whereas trajectories for reaction (3) appear to show no particular propensity towards either ET or SN2 products. The mechanistic diversity is consistent with the electron-donating ability of the ketyl species and steric bulkiness of chloroalkanes. We find that the trajectories have characteristics that reflect strongly the types of process [SN2 trajectories in reactions (1) and (3) vs ET trajectories in reactions (2) and (3)]. Trajectories that lead to SN2 products are simple with C-C bond formation and C-Cl bond breaking essentially completed within 50 fs. By contrast, trajectories leading to ET products are more complex with a sudden electron reorganization taking place within 15-30 fs and the major bonding changes and electron and spin reorganizations completed after 250 fs.

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