Ab initio quantum mechanical methods with the B3LYP/6-31G* method were used
to model the reactants, transition states, and products of Claisen rearran
gements of allyl vinyl ethers substituted at all positions with CN, NH2 or
CF3 groups. The calculations predict that 1-CN, 1-CF3-cis, 5-NH2, 6-CN, and
6-CF3 substituents increase the activation barriers, in agreement with exp
erimental results on substituent effects by CN, CF3, and the related 5-OCH3
example. All other substituents lower activation energies. A Marcus theory
type analysis was applied to separate the intrinsic and thermodynamic cont
ributions to the activation energies.