View source for Talk:Mod1:ch1508

1.2.1 Cp dimers:  You really think the endo conformation is that strange?  Would have been nice to have a little more about kinetic/thermo control.  Excellent discussion and nice to see a quantitative analysis of strain.

1.2.2 NAD:  A better way to comment on your minimisation (and to show off how much work you did) would be to plot a graph of energy vs. dihedral angle.  Sterics and electronic repulsion are not the same thing.

1.2.3 Taxol:  Your discussion is good but a little on the short side.  Energy for B is correct but A is slightly out as your structure is incorrect (look at the hydrogens on the cyclohexane).  Are there any particular interactions which would cause higher strain after hydrogenation of the alkene? 

1.3.1 Carbene: Your molecule has a plane of symmetry yet your orbitals are not symmetrical.  This is something I would have expected you to pick up on.  The problem is caused by a bug in MOPAC PM6.  Moral of the story: question the results the computer gives you, learn to identify these errors and how cope with them.   A deeper analysis of the interactions between the MOs would have been nice. 

Mini-project:   They could have used DEPT to assign the carbons, NOE will be the best way.  Good to see you graphically analysing the differences in calculated and experimental NMR. That’s a lovely bit of Paint work you’ve done there.  Good to see you’re thinking practically about other analytical techniques.  Having worked with very similar molecules, I can tell you that the best NOE interactions to observe are between the methylene group and the protons you’ve labelled C or D (if you want to differentiate between endo/exo isomers at least). 

Overall:  Discussions earlier in your report are perhaps a little low level (you should assume by now your audience does know something about chemistry), this doesn’t detract from the fact that they are good discussion though.  It is also good practice to number your compounds sequentially throughout rather than naming them (‘proline derivative’, ‘starting material’ etc).  A good report.