View source for Talk:Mod1:zy909

====Q1====
*Well researched and written introduction.
*"ring A (blue - see structure)" I could find this, even including the Jmol structures.
*It's not MM2 fault for not being able to predict the major product as implied in your text. We're only examining the products here. The question highlights that one need to consider all factors in a reaction before making prediction of the major product.
*Good arguments on the torsion and bend energy.
*you could have reported the bond angles for 3 and 4 to illustrate your point.
====Q2====
*"isomerises to the down position" should be "isomerises to the 'down' position"
*Reasonably optimised structures. But you didn't specify which method was used for the Jmol? Were the two results independently optimised by MM2 and MMFF94? Or did you use the optimised structure of one method and just calculate the energy using the other?
*Overall, I think you made very good analysis of the data from your "hyperstable alkenes" calculation. However, the work might have benefited from a more detailed explanation of "hyperstable alkenes". You're making the assumption that the readers know the subject.
*One important thing when comparing energies of different compounds (not isomer) is that you must balance the equation. In this case, the energy of H2 (0 kcal/mol) should have been mentioned in the comparison betwee3n 10 and 11.
====Q3====
*syn/anti terminology is preferred here for consistency with the question.
*The facial selectivity was well spotted and easy to explain. Maybe you should have explained it.
*You're the first one this year who put down why the calculated MOs were not symmetrical as they should be, and how to solve it.
*Your MOs were clearly visualised in Gaussview and not Chem3D. How were they calculated (PM6 or DFT)?
**''They were actually calculated by PM6 and visualised in Chem3D - I can provide the .c3xml files if required'' - [[User:Zy909|Zeqi Yang]] 17:36, 7 December 2011 (UTC)
*Correct analysis of HOMO and mixing between two MOs.
*How did you calculate your vibrational frequencies? It seems to me that structure 15 wasn't properly optimised.
*You forgot to measure the bond lengths to back all the arguments on bond strength up.

====Q4====
*The picture A/A' could have benefited from an clarification on the method used.
*The orientation of the 6-OMe group is quite interesting. In MM2, certain arrangement can bring the energy extremely low. I'm not sure I understand your argument that"this hampered the interaction between the 2-OAc and the oxonium". More clarification is needed here.
*The fact that you included the Jmol of all methods is much appreciated.
*A' (MM2) is off.
*Did you notice that for PM6, A = C, B = D? They are the same structure. Again, the almost identical energies are the clue.
*Your energies are generally alright, but the link to the experimental diastereoselectivity is missing. Energies of intermediates in different pathways are quite important when it comes to explaining the diastereoselectivity of the reaction.
====Mini project====
*5% for your own mini project
*Well defined question!
*The difference between experimental and calculated data shouldn't have been taken as absolute value. See the example from Rzepa and Braddock in my talk for data presentation.
*The comparison between calculated and experimental data you did is very tricky when difference were taken as absolute values.
*Generally the average difference is quite uninformative. We tend to focus on the C's we expect to have significant change in chemical shifts. The reason for the change in the carbonyl carbon chemical shifts is quite interesting here.
*Nevertheless, a quick look at your raw data led me to suspect (6S, 11R) to fit the chemical shifts of C6 and C11 better. Obviously, the project would have benefited much more from a discussion with us.