Talk:Mod:clc09mod3

Cope Rearrangement

Presentation:

Good use of Jmol and animations (Would be useful at times, to have direct on the page and not having to click on a tab). Data generally tabulated - good. Files shared throughout.

Results:

Anti and gauche conformers investigated and all re-optimised using higher level of theory. Correctly noted gauche 3 is lowest energy isomer in HF calculation, and the change in energetic ordering with a higher level of theory. Why could this be? Could consider MOs, vdW interactions etc. Where is the frequency or thermochemical data for anti 2?

Chair/boat TS: Both chair and boat TSs found, and energies and imaginary frequencies provided. Analysis of this data? What does this tell us? IRC calculations carried out for both chair and boat – good. Minimum found? Could have attempted different methods/approaches to find minimum.

Activation energies calculated for both levels of theory at 298K and 0K – good. What do the activation energies tell us about the reaction? Are they close to the reported literature values?

Understanding:

Good concise introduction, no use of conclusion. Steps taken quite clear, but could expand on why these steps were taken, why certain methods were used etc. Whilst your results are good, they require further analysis as to what they tell you. What information has this study provided?

Diels Alder

Presentation:

As above.

Results:

HOMO/LUMO of cis-butadiene good and the symmetries assigned in the ‘vertical plane’ column are correct. MOs for ethene?

Could do with files for TS MOs, as results aren’t as expected. If, as you’ve stated “the HOMO of the TS is a combination of the HOMO of cis-butadiene and the LUMO of ethene”, then shouldn’t the TS HOMO be antisymmetric down the vertical plane? Your image shows it as symmetric (although you have incorrectly assigned it as antisymmetric). Whilst you have explained HOMO/LUMO interactions, it would be useful to apply this to your results.

Exo/endo: Why do the MO diagrams not show the MOs for the entire TS? Can we gain any information from these MOs? Correctly noted endo is lower in energy. How can we explain this? Look for the presence of secondary orbital overlap vs steric interactions. The animations for the TS do not appear to show bond formation (rather molecules just moving closer). The bond 'forming' is very far (3.7 Angstroms) apart. This value is larger than twice the vdW radius of C and therefore doesn't suggest your calculations are showing bond formation. You have only provided files for the frequency analysis and not the optimisation and therefore I can't tell you if anything in the calculation set up is incorrect. IRC calculations carried out – good.

Understanding:

Could do with use of introduction and conclusion. Steps taken generally clear, but again no explanation as to why. In general, could do with a much more thorough explanation of the results. What do they show us? What information do they provide? And can we explain this? HOMO/LUMO interactions briefly explained. Could expand with allowed/forbidden reactions.