In reactions under kinetic control the products are less important for the calculation of activation energies.
It should be checked however that proposed TS's lead to the expected products. This is done by minimization of a structure close to the TS, or by an IRC calculation.

In bond forming reactions (additions, cyclizations), the TS geometry is most conveniently obtained from the product geometry, by gradually increasing the bonds in question.
An example is given in chapter 1E, where the TS for an Diels-Alder reaction is approached from the (norbornene) product side.

Back to Chapter 1, part A.