3C, Solvent effects
All semi-empirical programs (MOPAC, AMPAC, VAMP) have incorporated
In MOPAC the COSMO model has been implemented, which is invoked by the
The activation energy of almost any reaction will be influenced by the polarity
of the solvent. However, in a comparison of two reactions, the effects
may be similar, and cancel if the difference is calculated.
In paragraph 2A we mentioned an SN1 reaction, the dissociation of methyl
bromide, which doesn't display a maximum in energy in the range shown.
Now repeat this calculation after adding the keyword EPS=78.4 (submit
to power queue) and try to locate a maximum.
Also study the effect of substitution at the central carbon: ethyl bromide,
isopropyl bromide, tert.butyl bromide.
For an extensive presentation of all existing models (very nicely illustrated),
page on this subject.
This is part C of chapter 3: More theory
Previous part, B: FMO theory
Next part, D: Electrostatic interactions
Back to Chapter 3 Contents page.