Talk:Mod:BYL109

Q1

• Your energies for 3 and 4 are slightly off. I think it’s because you used hydrogenated product of 1 rather than 2, judging from the pictures you included.

• You correctly identified torsion as the main contributor to the difference in energy between 1 and 2, but did not explain which part of the molecules.

• I think you understand the contribution of bending energy to 3 and 4.

Q2

• “There are two things”. This isn’t very academic writing!

• “Apparently, the compound isomerises to the alternative” which compound? To which?

• Your optimised structures are not the lowest energy conformers, but close.

• How well does the MMFF94 data agree with MM2 data? A little bit more analysis here would go a long way.

• Decent account of the hyperstability of the alkene. Good use of visual aid.

Q3

• Cl2C: is an electrophilic carbene, and so would not attack LUMO. HOMO is what we need to worry about here.

• Most of your MOs look right, except LUMO+1

• You mentioned pi-sigma* interaction, but which pi? Which sigma*?

• Correct IR frequencies but you analysis is still very unclear to me.

Q4

• Correct choice of Me group and PM6 for the job.

• Structure A’ is a wrong isomer, not the same structure as A. B is more likely be B’. And your B’ is actually B, but in PM6 while the rest are in MM2. C returns an error of missing file. Your PM6 energies value are also higher than the global minima.

• Your explanation for stabilisation of A over A’ is rather vague. Showing your optimised structure with numbering would b much better.

• With PM6, A = C, B = D. This is due to the fact that PM6 handles quantum mechanics and treat electrons as belonging to the whole structure. Consequently bonds can be formed or broken to optimise energy.

• Your explanation of diastereospecificity is rather confusing.

Mini project

• Good statement of techniques used. However, you didn’t say which technique was employed to optimise the structure?

• Your structure of Cubebol is wrong. We’ll just have to work with this new structure now.

• C4, where the OH is, doesn’t give a good match between experimental data and predicted spectra. Neither is C15. I think the conclusion here must be that prediction doesn’t work well with this structure. But if we think about it carefully, you’re using the experimental data of Cubebol to fit a different structure -> no surprise it fails.