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Problems Set #7
General announcements:
1. The third quiz will be on April 27, 2004 in lecture.
2. The draft version for the paper is due on Friday, April 30, 2004 at 5 pm in YH1217.
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. A student acquires the GC/MS spectrum for his epoxide using a modified b-cyclodextrin column. One peak at t(r)=14.0 min has a absolute area of 100 units, while another one at t(r)=15.1 min only has 40 units. Both peaks show identical fragmentation in the mass spectrum and a [M]+-peak of 134 .
a. What is the advantage of using a cyclodextrin column here and instead of a HP-5 column?
b. Which conclusions can he draw from this data?
2. 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 the crude sample?
c. How does one know which solvent to use as mobile phase?
d. How do you find out which part of the eluent contains the desired epoxide?
e. Where is sand used in this step?