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The Effect of Microsolvation on E2 and S N 2 Reactions: Theoretical Study of the Model System F − + C 2 H 5 F + n HF
Author(s) -
Matthias Bickelhaupt F.,
Baerends Evert Jan,
Anibbering Nico M. M.
Publication year - 1996
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19960020212
Subject(s) - solvation , chemistry , density functional theory , gas phase , transition state , molecule , solvent effects , computational chemistry , thermodynamics , crystallography , solvent , physics , catalysis , organic chemistry , biochemistry
The model reaction system F − +C 2 H 5 F + n HF ( n = 0–4) has been investigated by use of a density‐functional method, in order to achieve a qualitative understanding of the effect of solvation on the E2 and S N 2 reactions. Two characteristic effects already occur upon monosolvation: a) the activation energies of the E2 and S N 2 pathways increase significantly and even become positive, because reactants are more strongly solvated than transition states; b) the S N 2 transition state is stabilized much more and becomes lower in energy than the anti ‐E2 transition state. This agrees with general experience from gas‐ and condensed‐phase experiments. The solvation is analyzed from two complementary viewpoints: a) as an interaction between solvent molecules and the F − /C 2 H 5 F reaction system; b) as an interaction between the [F − , n HF] solvated base and the C 2 H 5 F substrate. The extent to which condensed‐phase characteristics can be modeled by this microsolvation approach is discussed.