View source for Talk:Parrot on a diet=poly-no-meal

1.1   Your energies for 1 and 2 are very high!  Your structure 1 is missing, but 2 looks OK, so I'm not sure why.   Why is the endo-isomer kinetically preferred?   Energies for 3 and 4 are also far higher than they should be.   What is the reason for the greater torsional strain in 3?

1.2  Structure 5 looks OK, but what is its energy?   The other structure is missing from its purple box...  In fact, this compound prefers to have the carbonyl "down", so there is something wrong with your explanation for the observed stereochemistry.....   I don't understand your last comment about having dihedral angles drawn on the models to "save computer modelling" - how else would you measure the dihedrals if you didn't use a computer?

1.3  What are the energies of the two isomers?  In fact, the "down" isomer should be lower.   The low reactivity of the alkenes is more subtle than simply steric hindrance. 

1.4  Your 4 structures look fine - but again, what are their energies?  This problem probably requires more detailed modelling than the question/paper suggest, but you haven't really explained why e.g. the first of your structures can't cyclise fast.

1.5  IR frequencies fine, but you haven't explained why the exo and endo alkene stretches are different.  

Mini-project: Glad to see you chose your own!  However, the point of the exercise was to compare two isomers - and you seem to have just picked one molecule, although the paper does discuss conformers of each cation, which give different NMRs.   Then you got an "odd" cyclopropane structure...  I think this is because your starting structure (judging by the ChemDraw drawing) had an H on the ester carbonyl.  That structure would have two formal positive charges.  If you gave it only one in your optimisation, I can quite imagine that the optimisation would then lead to the cyclopropane.  Effectively, you'd have two adjacent trivalent centres which then form a bond.   Where was the charge located according to your calculations?  

Overall - you got there, but quite a few missing pieces of info (especially energies) and interpretation