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Q1
- Correct energies for 1 and 2. But wrong structures and energies for 3 and 4.
- You correctly identified torsion energy as the difference between 1 and 2, but failed to give the correct account of torsion energy.
- Dimeric and monomeric cyclopentadiene don’t exist in equilibrium. The dimerisation is pretty much one way at room temp.
Q2
- Correct lowest energy conformers.
- Decent comparision to MMFF94, although the relative difference in energy between 9 an 10 should have been commented on.
- You seem to understand the ‘hyperstable alkenes’ concept, but the explanation could have been clearer.
Q3
- Correct MOs. In later modules you may want to crop the picture to remove some of the background and improve the pictures’ quality.
- Correct prediction of reactivity.
- You completely ignore/miss the interaction between the anti pi bond and the sigma* orbital of C-Cl bond.
- The 1747 cm-1 frequency is wrong, did you optimise your structure before calculation?
- I would really love to see some comparison of bond lengths for C=C and C-Cl bonds.
Q4
- Correct choice of Me group.
- None of your A/A’ and B/B’ structures show any interaction between acetyl and the carbocation. Further optimisation is clearly needed.
- C and D seem to be too high in energy, check your ring conformation.
Mini project
- It’s very hard for me to compare your data with lit. values. A table will be much appreciated.
- What level of theory did you use for GIAO?
- There seem to be a clear difference between the calculated NMRs and the literature. What would help your comparison with the full assignment of all Cs in the structure so you can identify which ones are likely to be different between the two structures. I’m still not fully convince the data favours 15a (look at the low end of chemical shifts!)
- Overall, mini project as usual would have benefited from a discussion with us.
