Solvent Effects on Isotope Effects: Methyl Cation as a Model System

Date

2014-07-17

Advisors

Journal Title

Journal ISSN

ISSN

Volume Title

Publisher

American Chemical Society

Type

Article

Peer reviewed

Yes

Abstract

The isotopic sensitivity (CH3+ vs CD3+) of the equilibrium between the methyl cation in vacuum and in solution has been investigated. Two alternative options for describing the shape of the solute cavity within the widely used polarized continuum model for implicit solvation were compared; the UFF and UA0 methods give equilibrium isotope effects (EIEs) that vary as a function of the dielectric constant in opposite directions. The same isotope effect was also obtained as the average over 40 structures from a hybrid quantum mechanical/molecular mechanical molecular dynamics simulation for the methyl cation explicitly solvated by many water molecules; the inverse value of the EIE agrees with UFF but not UA0. The opposing trends may be satisfactorily explained in terms of the different degrees of exposure of the atomic charges to the dielectric continuum in cavities of different shapes.

Description

Keywords

Isotope Effect, Methyl Cation, COMT, Density Functional Theory

Citation

Wilson, P.B. et al. (2014) Solvent Effects on Isotope Effects: Methyl Cation as a Model System. The Journal of Physical Chemistry, 119 (3), pp. 802-809

Rights

Research Institute

Leicester Institute for Pharmaceutical Innovation - From Molecules to Practice (LIPI)