Talk:Mod:mw1409module3
Cope Rearrangement
Presentation:
Generally good use of images, with appropriate legends. Could have included images of the chair TS. Limited use of Jmol which would be useful at times to view the molecules from different angles. Good use of animations to illustrate IRC, animations for TS? Data not always tabulated, have to look through script to find values. Useful links to files.
Results:
Investigated anti and gauche conformers. Why didn’t you investigate gauche 3, which in Appendix 1 is the lowest energy conformer when optimising using HF/3-21g? Would you expect this to be the lowest energy conformer? You’ve mentioned that the lowest energy conformer would be expected to be anti.
Have re-optimized the anti 2 conformer – quite a large difference between the 2 structures, would you still describe the B3LYP optimised isomer as anti 2? Thermochemical data provided – good. Could have also run these frequency calculations at 0K. IR spectra?
Optimisation of chair/boat TS: Results good, images would be useful here. IRC present for chair and boat – with a number of methods investigated – v. good. Given data required to calculate activation energies. However it is unclear what activation energies were calculated. Value given for the activation energy for the chair TS at 0K using the B3LYP level of theory, and for the boat – is this also at 0K and using B3LYP? Could have calculated activation energies for both levels of theory at both temperatures and compared them to experimental data.
Understanding:
Brief intro given – could have been expanded (the same goes for the conclusion). Has explained why the steps were taken, and has an understanding of the methods used and their limitations.
Diels Alder
Presentation:
Good use of Jmol, and animations for TS. Data clearly tabulated. Useful links to files.
Results:
HOMO and LUMO provided for cis-butadiene, what about ethylene? Correct symmetries noted for cis-butadiene. Interactions between reactants for transition states good – could go into further detail here about allowed/forbidden reactions etc. Correctly noted C-C bond forming distance is <2xC vdW radius apart, therefore suggesting bond forming.
Endo/Exo: Results generally good. Correctly noted endo as lower in energy. Good animation of imaginary frequency and analysis of geometries. HOMO and LUMOs for exo and endo all antisymmetric – good. Interaction of reactants explained well.
Understanding:
Intro and conclusion a little too brief. Steps taken clear – perhaps include more justification for these steps – such as why certain methods chosen. Secondary orbital overlap and steric hindrance considered (could explain this a little further). Looked for secondary orbital overlap effect in results and showed not apparent in them. Very good use of reference to explain endo selectivity!