Talk:Mod:jh2810

Introduction

Absent

Cope rearrangement

All conformers identified. Good discussion about their relative energy but you should not only consider the steric effect but also the orbitals overlap that could lower the energy. When optimising the ANTI2 conformer using a more accurate method, did you use 6-31g basis set instead of 6-31g* (as it was asked in the wiki instructions)? Have you checked from your frequency calculation that your optimised ANTI2 conformer was a minimum on the PES (i.e. no imaginary frequency)? Chair TS optimised. Good interpretation of the ‘one imaginary frequency’. Be careful, a TS is not a global maximum: it is a maximum along the reaction coordinate (the coordinate that links the reactant and product identified by the imaginary vibrational mode) and it is a minimum in all other orthogonal coordinates. When optimising the Chair TS, you could have tried the second method with ‘Freezing the Coordinate’ even if your first try worked. Boat TS optimised. Good interpretation of the IRC calculation. You computed energies difference but be careful, in order to compare with experiments, you need to consider electronic and ZPE at least (and not only electronic energy). Have you concluded anything about the preferred mechanism? Any comments about the comparison between calculated and experimental values?

Diels Alder

What does the lowest real frequency suggest about motions that break the symmetry? (That at the TS this is uphill in energy). As well as butadiene HOMO and ethene LUMO, compare butadiene LUMO and ethene HOMO. Could draw a correlation diagram to show the FMO overlap clearly. “Therefore the activation is also smaller (by 0.96 kcal/mol) which explains why this is the thermodynamically more stable and favoured product.” Activation energy determines the kinetic product, Reaction energy determines the thermodynamic product. “However, it is possible that interactions between other lower lying molecular orbitals causes this effect.” And did you look for this and find it?

Overall

How do you ab inito or semi-empirical results compare to empirical rule such as the Woodward- Hoffmann rule for pericyclic reactions? Diagrams comparing what is expected and what was found would improve this report.