Isodesmic Reactions

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Isodesmic Reactions
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Isodesmic Reactions

• An isodesmic reaction is one in which the number
  and type of bonds in the reactants and in the
  products is the same.
• It may be a hypothetical reaction that is, one
  that could never occur.
• It is the best way to cancel out errors in
  computations, and get at the effect of a
  particular structural feature.

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Isodesmic Reactions
Isodesmic reaction scheme to test the
possibility of intramolecular stabilization of a
carbocation by fluorine
Calculate the energy of each geometry
optimized structure, then compute the DH of the
isodesmic reaction above using Hess Law. If
there is stabilization due to the F-C
interaction, the DH of the isodesmic reaction
should be negative
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Isodesmic Reactions
DHisodesmic rxn -2.7 kcal/mol