Bridging the gap between the gas phase and solution: transition in the kinetics of nucleophilic displacement reactions

Böhme, Diethard K.; Mackay, G. I.

doi:10.1021/ja00394a062

Cited by 181 publications

(149 citation statements)

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“…We use molecular dynamics computational simulation to examine model SN2 reactions roughly patterned after the CI + CH 3 CI reaction in water. The intrinsic SN 2 potential is taken to be the form of a double well, established in gas phase experiments 2 , 3 , 16 and quantum mechanical calculations,," 7 -20 but we take the methyl group as simplified to a single united atom. A fairly realistic model for flexible water is adopted.…”

Section: S'mentioning

confidence: 99%

“…(2.1) and (2.2) is intended to be a simplified representation of the model SN 2 reaction, C-+ CH 3 Ci --CICH 3 + C-, occurring in liquid water solvent. The total potential is composed of the potentials representing smaller parts of the problem as described below.…”

Section: B Potentialsmentioning

confidence: 99%

“…The total potential is composed of the potentials representing smaller parts of the problem as described below. 5 2 Gas Phase Potential Our SN2 gas phase potential is very roughly modeled after the one-dimensional Cl-+ CHIi --CH 3 Ci + C-ab initio gas phase potential of Jorgensen and co-workers., 9 The Jorgensen potential was only given along a reaction coordinate defined as the gas phase minimum potential energy path between reactants and products. To describe a full three-dimensional potential energy surface for our model SN 2 reaction we use a London-Eyring-Polanyi-Sato (LEPS) 27 potential energy function.…”

Section: B Potentialsmentioning

confidence: 99%

“…This incorporates the main features of the one-dimensional, double-well potential determined by Jorgensen, including the calculated barrier height, but uses a united atom representation for the central CHI group. The form of the LEPS potential is in which r, and r 2 are the variable bond lengths between the CH 3 united atom and the two Cl atoms, r 3 is the bond length between the two Cl atoms, and Qj and J are linear combinations of the "singlet" and *triplet* diatomic energies:…”

Section: B Potentialsmentioning

confidence: 99%

“…1 -3 This reaction is well known to be experimentally sensitive to solvent polarity," 4 and, beginning with the famous work of Hughes and Ingold, 5 7 solvent effects have been interpreted in terms of the equilibrium solvation thermodynamic free energies of activation of the transition state complex. This theme has been pursued in modem statistical mechanics in a Monte Carlo equilibrium simulation of CI-+ CH 3 Ci by Jorgensen and coworkers8 , 9 and in integral equation work by Chiles and Rossky. 10 In this paper we use the Molecular Dynamics simulation technique to explore a quite different and novel aspect of the reaction pathway: The role of polar-solvent dynamics and configurations in affecting, at the molecular level, the reaction trajectories and the value of the rate constant.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Molecular dynamics of a model S N2 reaction in water

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Gertner

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et al. 1987

The Journal of Chemical Physics

318

172

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Molecular dynamics are computed for a model SN2 reaction Cl−+CH3Cl→ClCH3+Cl− in water and are found to be strongly dependent on the instantaneous local configuration of the solvent at the transition state barrier. There are significant deviations from the simple picture of passage over a free energy barrier in the reaction coordinate, and thus, a marked departure from transition state theory occurs in the form of barrier recrossings. Factors controlling the dynamics are discussed, and, in particular, the rate of change of atomic charge distribution along the reaction coordinate is found to have a major effect on the dynamics. A simple frozen solvent theory involving nonadiabatic solvation is presented which can predict the outcome of a particular reaction trajectory by considering only the interaction with the solvent of the reaction system at the gas-phase transition barrier. The frozen solvent theory also gives the transmission coefficient κ needed to make the transition state theory rate agree with the outcome of the molecular dynamics trajectories. This theoretical κ value, which is the implementation for the SN2 reaction of the van der Zwan–Hynes nonadiabatic solvation transmission coefficient, is in good agreement with the trajectory results. In contrast, a Kramers theory description fails dramatically.

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Section: S'mentioning

confidence: 99%

Section: B Potentialsmentioning

confidence: 99%