Jump to content

Talk:Ef108M1:Imp3rial

From ChemWiki

Cp: Energies all seem fine (although too many dec. places given!) Why is the endo-isomer kinetically preferred? For 3 vs 4, the main difference looks to be the bend energy term.

NAD: Structures look OK (what were their energies?)

Taxol: Your energies are too high - can't see why for sure without rotatable (JMol) structures, but I suspect you have the "wrong" chair conformation for the 6-rings.

CCl2: Orbitals look OK. Your discussion of stretching frequencies is a bit confused/confusing - the C=C anti to the alkene should have the lower stretching frequency. Did you analyse the geometries (bond lengths)?

Mini-project: Although it's a bit hard to tell without rotatable structures, it looks to me like your "Cis-trans" isomer is an incorrect diastereomer...the tBu group on R-3C and the OH on R-5C should be cis, and they look trans- to me... This is on top of the fact that, as you say, you may have located a boat conformation instead of a chair. For the "missing peaks" for the 13C of the all cis-isomer - have a look at the structure and think about its symmetry properties. I agree that 1H-1H J values are the key thing to analyse for this project. All in all, it would have been good to apply thought at an earlier stage of the project. Good attempt at getting the calculations done, though.