Talk:Mod:thatssoraven
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Q1
- "ab inition" should be "ab initio".
- Correct energies for 1, 2, 3 and 4. I got 99:1 for exo:endo under equilibrium. Far higher ratio for 3 and 4. You might have mistaken kcal/mol for kJ/mol.
- "where the reduction is thermodynamically controlled, under conditions such as Pd/C + H2 this wouldn't be the case because the bridgehead carbon would likely hinder access to the C1-2 double bond". In fact unless under exceptional circumstances, all hydrogenation are under kinetic control! The whole analysis of 3 and 4 is just for a good story.
Q2
- I think the same mistake for your population calculation.
- Your analysis was decent, but you should have specified which method was used for calculation.
- You have not compared the results of MM2 and MMFF94.
- I think you get what hyperstable alkenes are about, but could have explained it better. In which molecules do they often happen? and where in the molecule?
Q3
- Correct choice of double bond reactivity, correct MO, although pictures could have been easier to see.
- I can't find the structure of 12a.
- You mention interaction between the anti double bon and LUMO+1 in the IR calculation, but this was not shown in your MOs.
Q4
- Correct choice of the Me group.
- Why is A' PM6 N/A?
- Same ChemDraw structure for B and B'. I can't get the same energies as yours using the Chem3D files you supplied for B and B'. The values I have are much higher.
- With both A and B, your optimised energies are close, but not quite the lowest. Your C and D optimised structures are spot on.
- Corrected c3xml files were sent to me on 26/10, some of the originally reported energies were not reproduced but the mistakes with structures were corrected.
Mini project
- 5% for coming up with your own project.
- Biological systems pi-stacking are often in water -> hydrophobic groups stay together. In THF, their proposal is far less likely.
- Decent trashing of the 'proposed' pi-stacking.
- Comparison between ALPHA and BETA: your numbers tell me ALPHA is more stable, by 0.01347 Hatree = 8.46 kcal/mol. MASSIVE! Ouch!
- Comparison of 13C NMR: The key 13C NMR signal here is that of the C-OH where the stereochemistry is different betweeh ALPHA and BETA. One would expect significant difference here due to the inherent strain of trans-[3.3.0] bicyclic structure. This chemical shift is typically 60-80 ppm and if you have a careful look at the numbering in Gaussian, you will find your carbon and the rather differently predicted chemical shifts for the two structures.