User talk:Xx108(module 3)
Cope Rearrangement
Presentation:
Data clearly tabulated. Good use of images and Jmol. Could do with animations to show imaginary vibrations. Links to some of the original files provided.
Results:
Many anti and gauche conformers considered. Correctly noted gauche 3 is lowest in energy and rationalised using MOs – good.
Anti 2 – Reoptimised. Note, you cannot compare energies between different methods (HF and DFT) - they’re calculated on different energy scales. Good comparison of geometries for both. Thermochemical data provided. Thermochemical energies (e.g. sum of electronic and thermal energies, sum of electronic and thermal enthalpies) at 0K should all be the same as thermal energies should all be 0. The link to the 0K calculation does not appear to be the right one, as there is no frequency analysis, or setting the temperature in this file.
Boat/Chair TS: Results good. IRC calculations for chair – have attempted a number of methods. Boat? Activation energies calculated for chair and boat at both levels of theory at 0K and 298K – v. good.
Understanding:
Good concise intro and conclusion. Steps taken very clear, and have rationalised these steps and the advantages/disadvantages of different approaches – good. Also good explanation of results obtained. Appropriate references made to primary literature.
Diels Alder
Presentation:
Same as above
Results:
MOs of reactants good with correct symmetry assigned. Interactions of these MOs and allowed reactions mentioned. MOs of TS – good with correct symmetry. Correctly noted the C-C bond bonding distance is < 2 x vdW radius of C, suggesting bond forming. Calculated activation energy using 2 different levels of theory as extra work and compared to literature value – excellent!
Endo/exo – results v. good. Investigated 2 different levels of theory for TS optimisation. Correctly noted endo is lower in energy. Good consideration of steric reasoning vs. secondary orbital overlap effect.
Understanding:
Nice introduction. Good understanding of the work being done and limitations of the calculations carried out. The method of TS optimisation has been carefully considered looking at the advantages/disadvantages of each. Suggestions for possible further work also mentioned . Results well analysed including considering HOMO/LUMO interactions and allowed/forbidden reactions. Also provided a very good explanation of secondary orbital overlap with use of diagrams – but are these apparent in your MOs?