Talk:Km1710

Introduction Very good general introduction.

Cope rearrangement Some conformers were successfully identified. Good discussion about their relative energy. Frequency calculation correctly interpreted. Good discussion about the different methods to optimize a TS. Chair and Boat structures successfully identified with the different methods proposed. IRC calculation successfully done and interpreted. Good conclusion about the preferred mechanism.

Diels-Alder The structure labelled butadiene in “4. Yield of Reaction” is in fact 2-butene. Butadiene is stable wrt cis-trans isomerization as it would require conjugation to be broken. Secondary overlap suggests that interaction between pi orbitals not involved in the bond forming reaction stabilise the TS. This is based on an FMO approach but it is debatable whether calculations support it (http://pubs.acs.org/doi/abs/10.1021/ar0000152).

There are some misunderstandings in the text:

• Differences compared to experimental spectrum spectrum also because real molecular vibrations are anharmonic, and coupled.

• Approximate Hessians may affect convergence of a geometry optimisation, but with updating based on exploring a potential energy surface, convergence can often be improved.

• Can't compare energies between different methods and basis sets.

• Activation energy doesn't increase with temperature, but there are more molecules with energy above the activation barrier, and more with energy along the right coordinates for reaction to take place.

References to original literature supplied, and helpful use of JMol structures.