Talk:Mod3:YJY1234
Cope Rearrangement:
Presentation:
Data generally tabulated. Images provided - would have been easier to assign images to the different conformers at the beginning rather than having to scroll back. Good use of animations for vibrational frequencies. Use of Jmol would be useful in places to visualise molecules from different angles. Use of file sharing?
Results:
Optimized gauche and anti structures and correctly noted gauche 3 is lowest energy conformer at this level of theory. Reasoning why? Could consider vdW interactions, MOs, etc. Anti 2 reoptimised and frequency analysis carried out. IR spectra – good, and thermochemical data provided. Same for 0K?
Chair/boat TS : Results ok. Energies for the boat and chair TSs? IRC carried out – would be good to include the graphs for these, to see if have reached a minimum. Same for boat? Activation energies calculated for both levels of theory for chair and boat. Activation energies at 0K? Note, you cannot compare energies between different methods (HF and DFT), they’re calculated on different energy scales.
Understanding:
No introduction or conclusion. Steps taken clear. Could expand on reasoning for methods/levels of theory/use of keywords etc. Perhaps a little confused here ‘The first method is to use Hartree Fock and the default basis set 3-21G . The second method is the frozen coordinate method.’ The HF/3-21g is the level of theory. The frozen co-ordinate method is a method of optimisation – they are not mutually exclusive.
Diels Alder:
Presentation:
As above. Have included some file sharing in this section. Use of animations for vibrational frequencies?
Results:
HOMO/LUMO of cis-butadiene good and correct symmetries assigned. Same for ethylene? Included MOs of TS. Would you expect the HOMO TS to be symmetric? Good explanation of HOMO/LUMO interactions.
Endo/exo: Reactants and TS MOs provided. Assigned HOMO of exo as symmetric, are you sure? Correctly noted endo as lower in energy. Have rationalised this using steric reasoning as well as secondary orbital overlap. This is explained very well with the use of diagrams. Have considered kinetic and thermodynamic control – good. When analysing C-C distances could have noticed C-C bond forming distance is <2 x vdW radius of C, suggesting a bond is forming.
Understanding:
No introduction. Steps taken provided, again explanation as to why certain methods/levels of theory etc. were used could be expanded on. HOMO/LUMO interactions for TS well understood – could expand onto allowed/forbidden reactions. Good explanation of results from endo/exo – and nice conclusion to this section.