Issue 37, 2014

Solvent effects and potential of mean force: a multilayered-representation quantum mechanical/molecular mechanics study of the CH3Br + CN reaction in aqueous solution

Abstract

The bimolecular nucleophilic substitution (SN2) reaction of CH3Br and CN in aqueous solution was investigated using a multilayered-representation quantum mechanical and molecular mechanics methodology. The reactant complex, transition state, and product complex are identified and characterized in aqueous solution. The potentials of mean force are computed at both DFT and CCSD(T) levels of theory for the reaction region. The CCSD(T)/MM level of theory presents a free energy activation barrier height at 19.1 kcal mol−1 which agrees very well with the experimental value of 20.7 kcal mol−1, while the DFT/MM level of theory underestimated the barrier height at 16.5 kcal mol−1. The results show that the aqueous environment has a significant contribution to the potential of mean force. Both the solvation effect and the polarization effect increase the activation barrier height by ∼14.5 kcal mol−1 and the solvation effect plays a major role by providing about 70% of the contribution.

Graphical abstract: Solvent effects and potential of mean force: a multilayered-representation quantum mechanical/molecular mechanics study of the CH3Br + CN− reaction in aqueous solution

Article information

Article type
Paper
Submitted
14 Jun 2014
Accepted
06 Aug 2014
First published
07 Aug 2014

Phys. Chem. Chem. Phys., 2014,16, 19993-20000

Author version available

Solvent effects and potential of mean force: a multilayered-representation quantum mechanical/molecular mechanics study of the CH3Br + CN reaction in aqueous solution

Y. Xu, J. Zhang and D. Wang, Phys. Chem. Chem. Phys., 2014, 16, 19993 DOI: 10.1039/C4CP02635G

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