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Problems Set #6
ATTN: answers to the below questions are due at the start of your lab period of Meeting 6; these answers should be part of your pre-lab write-up.
Announcements:
1. Make sure that you make progress on your formal report as well in terms of literature research and writing the parts that you completed already in the lab. The draft version of paper is due on April 24, 2009 at 5 pm. The draft version is worth 15 points, the final paper 45 points. For more information what the draft is supposed to contain see here. Late submission will receive less credit. The more of your work you submit in the draft, the more feedback you will get, which will beneficial for the final version. We will try to return the reports by Monday, April 27, 2009.
2. It is highly advisable to look at the reader prior to attending to lecture. There are a lot of issues to discuss in the individual experiments, but not enough time to discuss every little thing in great detail. It is also recommended to review the techniques that should be familiar to you from 30AL/BL i.e. extraction, recrystallization, TLC, IR/NMR spectroscopy, etc.
And now to the fun part...the prelab questions:
1. Referring to the catalyst design, answer the following questions.
a. What is the function of the tert.-butyl groups in the catalyst? Can they be replaced by methyl groups?
b. How can the structure of the catalyst be described in terms of the Mn-atom?
c. What is the function of the cyclohexane part in the catalyst?
d. Why is manganese used as central atom here?
2. Referring to the epoxidation reaction carried out in the lab, answer the following questions.
a. A student uses hexane as solvent for the reaction. Which problem does this choice pose?
b. Why is it imperative to use a buffer in this reaction?
c. Why is it important to work up the reaction immediately after the reaction is completed?
d. The student starts off with a solvent mixture of dichloromethane:hexane=1:1 for TLC. The procedure asks to optimize the mixture. What does this mean and how is this accomplished? Why is this optimization important?
e. How are the alkene and the epoxide being visualized? Outline a brief procedure.
f. Another point that was stressed in lecture was the removal of the catalyst from the crude product. How is this accomplished and why is this necessary?