Talk:Mod:479231

Introduction

Good introduction.

Cope rearrangement

Some conformers successfully optimised ­although not all of them. Good comment about their relative energy. Be careful: “This is a difference in energy from the lower basis set of (234.61171-­231.69254) 2.91917 a.u which is equal to 1831.81 kcal/mol. This is a large difference in energy and shows that using a more accurate basis set gives a vastly different result.” you should not compare absolute energies computed with different methods, as they're on different energy scales. Good interpretation of the frequency calculation. Transition states successfully optimised with the different methods suggested. You correctly checked the presence of one imaginary frequency. Good interpretation of the IRC calculation and good conclusion about the preferred mechanism.

Diels-­Alder cycloaddition

The HOMO you have drawn for butadiene + ethene looks symmetric. It is suprising the HOMO and LUMO are the same symmetry as they should result from the formation of either the anti­symmetric pair of fragment orbitals, giving rise to a fragment MO (or the same for the symmetric pair). The lowest real frequency is symmetry breaking, suggesting that this motion is uphill in energy (and would not occur). Can you label the SOO interactions in the computed MO diagrams? Extra discussion on this: <http://pubs.acs.org/doi/abs/10.1021/ar0000152>