3C, Solvent effects

All semi-empirical programs (MOPAC, AMPAC, VAMP) have incorporated solvent models. (Short note in Dutch.)
In MOPAC the COSMO model has been implemented, which is invoked by the keyword EPS=n.nn.
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), see Mike Colvin's page on this subject.


This is part C of chapter 3: More theory
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