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Problems Set #7
General announcements:
1. The draft version for the paper is due on Friday, February 2, 2007 at 5 pm in YH3077E.
ATTN: answers to the below questions are due at the start of your lab period of Meeting 7; these answers should be part of your pre-lab write-up.
1. The last step of the epoxidation involves flash chromatography.
a. What is the purpose of this step?
b. Why and where is sea sand used to prepare the column?
c. A student forgets to pre-treat the stationary phase with a 1% NEt3 solution. What would be most likely observe?
d. How do you find out which part of the eluent contains the desired epoxide?
2. NMR spectroscopy
a. Which solvent is used to acquire the NMR spectra of the final product? Why?
b. What is the "proper" labeling for the NMR tube?
c. Which information can one extract from the 1H-NMR and the 13C-NMR spectrum?
3. A student acquires the GC/MS spectrum for his epoxide using a modified b-cyclodextrin column. Which conclusions can the student draw from the data below?
| time (min) | area (units) |
| 1.25 | 5000 |
| 5.10 | 500 |
| 9.85 | 700 |
| 10.15 | 300 |
| 10.5 | 100 |
Note: The last three peaks exhibit the same molecular weight.