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Problems Set #4
ATTN: answers to the below questions are due at the start of your lab period of Meeting 4; these answers should be part of your pre-lab write-up.
The draft version of paper is due on 1-31-2003 at 5 pm in YH 1217. The draft version is worth 15 points, the final paper 35 points. The draft version should contain the following parts: Abstract, complete introduction, complete discussion of steps 1, 3, 4, and 5, complete experimental part for steps 1,3,4, and 5, spectra discussion for Step 1, 3, 4, and 5,and references. Do not include an essay certain techniques e.g. TLC, GC, NMR etc work. The final paper should not be longer than 15 pages (~1-2 page introduction, 6-7 pages discussion, ~4-5 pages experimental, 3-4 pages spectra section, ~1 page conclusion + references). The draft version should be double spaced with 1'' border for the grading.
1. Why do you use a staining solution in order to visualize the spots on your TLC plates during the epoxidation? What do you expect to observe?
2. What is the source of the oxygen in the formation of the epoxide? Which other oxygen sources could you use with this catalyst?
3. How can you determine the composition of your compound in terms of enantiomers? Explain briefly.
4. How could you improve the ee for your reaction?
5. What are possible byproducts that contaminate your product? How do you explain their presence?
6. Which information do you get from the [a]D of your ligand?
7. Using Spartan, perform a PM3 calculation for Mn(salen)Cl and SalenH2. Based on the calculation, answer the following questions:
a. How does the C=N-distance in the ligand change as you go from SalenH2 to Mn(salen)Cl? How could you detect the change using spectroscopic techniques available to you?
b. How do the Mn-O, Mn-N, Mn-Cl (in Mn(salen)Cl) and the O-H and N-H distance compare to the published values from crystal structures?
c. How do the observed O-H-distance and the N-H distances compare to the the bond distances found in NH3 or H2O? What are the consequences?