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Problems Set #7
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. Some of the students will add pyridine N-oxide to their reaction mixture. What is the function of this compound? Show approriate intermediates.
2. Why is the epoxidation carried out in a two-phase system? Explain briefly.
3. A student acquires the GC/MS spectrum for his epoxide using a cyclodextrin column. One peak at t(r)=11.0 min has a absolute area of 120 units, while another one at t(r)=11.2 min only has 40 units. Both peaks show identical fragmentation in the mass spectrum.
a. Assuming that the student used styrene, assign the peaks.
b. Determine the ee-value for the reaction.
4. The last step of the epoxidation involves a flash-chromatography.
a. What is the purpose of this step?
b. Why is it necessary to treat the column with triethylamine prior applying teh crude sample?
c. How does one know which solvent to use for elution here?
d. How do you find out which part of the eluent contains the epoxide?