Talk:Mod:YYTmod3
Cope Rearrangement
Presentation:
Data clearly tabulated. Figures and Tables given appropriate legends. Animations would be useful at times (e.g. to illustrate imaginary frequencies). Appropriate links to files given. Note you have misquoted 3-21g as 3-21 a number of times in the script.
Results:
Optimized anti and gauche conformers inc. gauche 3 - good. This is the lowest energy isomer according to these calculations, would you expect this? For the HF and B3LYP optimised anti-2 conformer you cannot compare energies between different methods (HF and DFT) - they’re calculated on different energy scales! Further comment on their geometries? Included IR spectra and thermochemical data – good. Calculations at 0K?
Chair/Boat TS: Results generally good. Images of optimised structures would be useful. Also please note the frozen co-ordinate method is a 2 step approach – the reason the structure/energy from the ’2nd’ optimization is different to the ‘1st’ and ‘3rd’ is because bond lengths are constrained in this stage. Once the whole molecule is optimised free of constraints (in the 3rd optimisation) the chair TS has a similar energy and structure to that from the TS Berny method. IRC calculations carried out for the chair structure using a range of methods – good. Could do the same for the boat structure.
Activation energies calculated for both levels of theory at 0K and 298K – very good. Good comparison to experimental data.
Understanding:
Good concise introduction and have summarised findings well at end. Steps taken clear. Could comment more on why these steps were taken, why a certain level of theory was used, use of keywords etc. Good explanation of the IRC method.
Diels Alder
Presentation:
Data clearly tabulated. Good use of images and Jmol. Animation of TSs would be useful. Appropriate links to original files provided.
Results:
MOs of butadiene good – correct symmetry noted. MOs for ethylene?
TS – Results generally good. See above for comments on frozen co-ordinate method. Correctly noted the C-C bond forming distance is < 2 x vdW radius of C, thereby showing shared electron density. Good explanation of the interaction of the reactants – diagrams assist explanation well.
Exo/endo: Results generally good. Correctly noted endo lower in energy. Could comment on the symmetry of the TSs and comment on the interaction of the MOs of the reactants as in the previous section. Have reasoned endo is lower energy due to secondary orbital overlap effect – good. Can you see this effect in the MO diagrams?
Understanding:
Could do with more than a line for the introduction/conclusion. Steps taken generally clear. Could add reasoning as to why these steps were taken, e.g. why use of opt=noeigen in TS optimisation? Interactions between MOs of reactants and allowed/forbidden reactions good. As mentioned above, secondary orbital overlap effect is discussed – would be good to apply to your results.